Class Ix Biology Book Notes 4q462

Biology

Sindh Text Book Board, Jamshoro.

SECONDARY STAGE BIOLOGY BOOK ONE

FOR CLASS IX

For

Sindh Textbook Board, Jamshoro.

Book arranged by www.mynoteslibrary.com

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CONTENTS SECTION

1

LIFE AND ITS ORIGIN

CHAPTER

1

INTRODUCTION TO BIOLOGY

SECTION

2

ORGANIZATION OF LIFE

CHAPTER

2

STRUCTURAL ORGANIZATION OF LIFE

SECTION

3

BIODIVERSITY

CHAPTER

3

CLASSIFICATION OF LIVING ORGANISMS

40

CHAPTER

4

VIRUSES, BACTERIA AND CYANOBACTERIA

45

CHAPTER

5

FUNGI AND ALGAE

53

CHAPTER

6

BRYOPHYTES AND TRACHEOPHYTES

58

CHAPTER

7

INVERTEBRATA

65

CHAPTER

8

CHORD ATA AND VERTEBRATA

71

SECTION

4

MAINTENANCE OF LIFE

CHAPTER

9

FOOD AND NUTRITION

78

CHAPTER

10

RESPIRATION

102


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Chapter 1 INTRODUCTION TO BIOLOGY Biology, the study of life is the most vital and challenging branch of science. Why? Because it is concerned with and affects all the aspects of human life. This field is ever growing, as old questions are answered and new questions are raised. When and where living organisms originated? How do they grow? How did this diversity of organism come into being? Who created it? This is just a glimpse of questions, biologists are working upon right from the day one. They are using this acquired knowledge of the basic natural processes for the welfare of mankind. Learning objectives:     

Definitions of biology and other branches of biology. Relationship of biology with other sciences. Biological methods of study. Contribution of medieval are recent Muslim and other Biologists Islamic and other views about origin of life on earth.

The word science is derived from a Latin word meaning "to know" Science is a way of knowing. It emerges from our curiosity about ourselves, the world and the universe. Science helps human beings to understand the natural world and is concerned solely with information gained by observing and testing that world. Natural world cannot be understood with out asking questions, like how did variety of living things evolve on earth? In what way they interact? What processes must occur in each organism? Why living things differ from non-living? Common questions like these form the basis of the science of biology. 1.1 WHAT IS BIOLOGY? On your way across school campus take a moment to look around you. You will notice a variety of organism around you, e.g. sparrows, squirrels trees, bushes, grasses etc. In addition to the countless tiny ones. These all living things are studied under the head of scientific discipline called Biology. The word biology is composed of two Greek words bios meaning life and logos meaning discourse, thought, and reasoning or in simply the study. It is a branch of natural science that deals with organisms and different phenomena of life. Biology is further divided into two main branches i.e. Botany and Zoology. Botany (Gr: Botane means plants) is a branch of biology which deals with scientific study of plants while Zoology (Gr: Zoo means animals) deals with the scientific study of animals. According to the revised classification system all the small, usually, microscopic organisms which were previously classified as plants or animals have now been separated into independent groups. Study of these micro-organisms is called Microbiology. The study of biology provides information about: 1) 2) 3) 4) 5) 6) 7)

Various kinds of living organism existing on earth. Relation of existing organisms with extinct organisms. Identification and grouping of living organisms on the basis of similarities, dissimilarities and relationship. Structure, function of an organism. Inheritance of characters from one generation to next generation. Relationships of organisms to their environment. Harmful and beneficial effects produced by different living organisms etc


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1.2 QURANIC TEACHING ABOUT ANIMALS AND PLANTS LIFE Almighty Allah has conveyed a great knowledge about animals and plants through our Holy book the Quran. A few of the Ayah are quoted as under: It says about the origin of life that; "We made every living thing of water. Will they not then believe?" (Surah Al-Anbiya, Ayah 30) "And Allah has created every animal of water. Of them is (a kind) that goes upon its belly and (a kind) that goes upon two legs and (a kind) that goes upon four. Allah creates what He will. Lo! Allah is able to do all things." (Surah Al-Nur, Ayah 45) An Egyptian mufassir, Allama Abdullah Yusuf Ali has symbolised water with the protoplasm and thus explains that the protoplasm is the basis of all living matter and "the vital power of protoplasm seems to depend on the constant presence of water." "He it is who sends down water from the sky and therewith we bring forth buds of every kind; We bring forth the green blade from which we bring forth the thickclustered grain; and from the date-palm, from the pollen thereof, spring pendant bunches; and (we bring forth) gardens of grapes, and the olive and the pomegranate, alike and unlike. Look upon the fruit thereof, when they bear fruit, and upon its ripening. Lo! Herein verily are portents for a people who believe." (Surah Al-An'am, Ayah 100) Holy Quran has explained the significance of water for plants and animals at several places. "Who has appointed the earth as a bed and has threaded roads for you therein and has sent down water from the sky and thereby We have brought forth divers kinds of vegetation." (Surah Ta-ha, Ayah S3) Glorious Quran has also revealed some facts about the growth and variety of plants. "And in the Earth are neighbouring tracts, vineyards and ploughed lands, and date-palms, like and unlike which are watered with one water. And We have made some of them to excel others in fruit. Lo! herein verily are portents for people who have sense." (Surah Al Ra'd, Ayah 4) "Lo! Allah (it is) who splitteth the grain of corn and the date-stone (for sprouting). He brings forth the living from the dead, and is the bringer-forth of the dead from the living. Such is Allah. How then are you pervented?" (Surah Al-An'am, Ayah 96) Above age refers to the wonderful act of production and also interaction of living and dead. Allah has also indicated the usefulness of some of the plants and animals to the human welfare. The following Ayah can be quoted for reference.


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"And Lo! In the cattle there is a lesson for you, We give you to drink of that which is in their bellies, from betwixt the refuse and the blood, pure milk palatable to the drinkers." (Surah An-Nahal, Ayah 66) "And the earth have We spread out and placed therein firm hills, and caused each seemly thing to grow there in." (Surah Al-Hijr, Ayah 19) The

Holy

Quran

also

informs

us

about

the

mechanism

of reproduction.

"Glory be to Him Who created all the sexual pairs, of that which the earth groweth, and of themselves, and of that which they know not!" (Surah Ya-sin, Ayah 36) "And thy Lord inspired the bee, saying: choose thou habitations in the hills and in the trees and in that which they hatch; then eat of all fruits, and follow the ways of thy lord made smooth (for thee). There cometh forth from their bellies a drink diverse of hues, wherein is healing for mankind Lo! Here is indeed a portent for people who reflect." (Surah Al-Nahal, Ayah 68-69) 1.3 BRANCHES OF BIOLOGY Nearly two million species (kinds-types) of plants and animals are known to the world. Modern biology does not concern only with the recognition and classification of these species but also deals with their structural and functional aspects. Extensive research during the 20 century has led to the division of biology into a large number of specialized branches. Some of the important branches of biology common to botany and zoology are: i)

Morphology (Gr: Morphe = form): This branch deals with the study of external structural characteristics of plants and animals.

ii)

Anatomy (Gr: Ana = up, tome = to cut): It deals with the internal structures or organs of an organism. In plants it deals with the arrangement of different types of tissues in root, stem leaf etc.

iii)

Histology: (Gr: Histos = web or tissues): It deals with the study of tissues of plants and animals under a microscope.

iv)

Cytology or Cell-Biology (Gr: Kytos = hollow vessel or cell): The study of structure, function and composition of cell and cell organelles is called cytology or cell-biology.

v)

Physiology (Gr: Phusis = nature): It is the study of functions of different parts of living organisms.

vi)

Ecology (Gr: Oikos = home): It is the study of relationships of living organisms with each other and with their non-living environment. It is also called environmental biology.

vii)

Embryology (Gr: Embryon = embryo) or developmental biology: It is the study of progressive developmental changes which occur after zygote formation upto an organism is formed.


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viii)

Taxonomy (Gr: Taxis = arrangement or grouping; Noms = laws related to naming): It deals with the description; identification, classification and scientific naming of living organisms, according to their similarities and dissimilarities.

ix)

Genetics (Gr: Genesis = origin): It deals with the study of inheritance including transmission of hereditary characters from parents to their offspring.

x)

Palaeontology (Gr: Palaios = ancient, ontos = being organisms): It is the study of animals and plants that lived in the remote past and are now found as fossils in the rocks. It can be further divided into two branches i.e. Palaeobotany; study of plant fossils, Palaeozoology, study of animal fossils.

In the ancient past fossil fuel.

large quantities of dead organisms were fossilized and formed coal, oil and other

xi)

Biochemistry: It deals with the chemistry and chemical aspects of the living system.

xii)

Microbiology (Micro = very small): It deals with the study of microscopic organisms such as viruses, bacteria, etc.

xiii)

Biotechnology: It is the manipulation of living things (animals, plants, micro-organism) for the welfare of mankind. Recently methods of genetic engineering have brought about a revolution in this field. By using these techniques not only yoghurt, cheese, bread, insulin, antibiotics etc. Are being produced but number of diseases are cured.

1.4 BIOLOGY AND OTHER SCIENCES Biology is a multi dimensional science. It is linked with the knowledge of chemistry, physics, mathematics, sociology, statistics etc. and these branches which are related to biology are biochemistry, biophysics, biometry, etc. Some of them are discussed below. 1.

Biochemistry: A complete branch of chemistry which requires firm knowledge of biology and chemistry to explain the synthesis of biomolecules, their requirement and the effect caused by the deficiency and efficiency of different molecules on the organisms and their metabolism.

2.

Biophysics: Branch of physics where we apply laws and techniques of physics to explain the metabolism of living organism, to find out the age of fossils etc. One of the sub-branch of biophysics is Radio-physics, where radioactive isotopes are used to trace the translocation of different material "in vivo", that is, within the living organism. Radio labeling and carbon dating also show some uses of radio active isotopes in determining the age of fossils. Use of sound waves as ultrasound and laser technology show some relationship of physics with biology.

3.

Biometry: It is branch of mathematics where data and measurements related to living organisms are dealt with. Without knowledge of mathematics and statistics no biological research and data analysis is possible. All biologists conclude their results by using knowledge of


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statistics

and

mathematics.

4.

Behaviourial biology: Many of the facts of biology are reflected in the study of behaviour it is an intersection of biochemistry, genetics, physiology, evolutionary theory and ecology.

5.

Biosociology: The study of behaviour, especially social behaviour, also associates biology to the social sciences and humanities. Through the study of life in general, we will learn more about ourselves.

Finally, we can say that biology is related with each branch of science. 1.5 BIOLOGICAL METHOD A biological method is a scientific approach used to resolve a biological problem related to or produced by a living organism. In order to resolve a specific biological problem a biological method is adopted, which consists of following steps. (i) Observation (ii) Hypothesis (iii) Deduction (iv) Experiment (v) Result (vi) Law or theory 1. Observation: Most of the biological investigations start with an observation. After selecting, specific biological problem, observations are made to collect relevant information. For example; take the case of malaria. Malaria is a the greatest killer disease of man for centuries. Malaria was the one among many other diseases for which a cure was needed. In 1878, a French physician, Laveran, studied the blood sample of malaria patient under microscope and observed tiny creatures in it. These creatures were later named Plasmodium. 2. Hypothesis: In the light of observed facts and previously collected information (data) biologists make 'intelligent guesses' as to what may be the possible answer to this particular question. This intelligent guess in a form of a statement is called hypothesis. So, the hypothesis is a statement made by scientists about a certain phenomenon, on the basis of available information. For example, an observation was made that Plasmodium is present in the blood of malaria patients. So a question was raised, is Plasmodium the cause of malaria? It would be a good guess to say 'yes' but it is only a guess which can be presented as a hypothesis that: "Plasmodium is the cause of malaria”. 3. Deduction: To test the hypothesis certain deductions that are logical prediction are made. In other words deduction is the logical explanation of a hypothesis. It does not require any type of experimentation. For example, to test the above hypothesis the following deductions were made. "If Plasmodium is the cause of malaria, then all the patient suffering from malaria should have malarial parasite in their blood while healthy people should not have". A number of deductions can be made to explain the hypothesis. These deductions can be tested and verified by experiments. 4. Experiment: The next step is to test each deduction (prediction) practically to find out whether or not the hypothesis is correct. In testing the deduction we are actually testing a hypothesis. This is where the scientist shows his skill as an experimenter. For this


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purpose, scientist performs two types of test i.e. control and experimental groups. Control group means a group of healthy people and experimental group means group of malaria patients. Both groups were kept in identical conditions. In order to find out the real cause of malarial, scientists examined the blood of about 100 malaria patients and also examined the blood of 100 healthy persons. 5. Result: From above experiment it was found that all the malarial patients had Plasmodium in their blood, where as the blood of healthy persons were free from Plasmodium. These results verified the deduction and finally the hypothesis i.e. "Plasmodium is the cause of malaria". 6. Theory: It is not always possible to confirm a hypothesis immediately. The validity of a hypothesis rests on a gradual accumulation of indirect evidences. As more and more evidence come to hand, the hypothesis gain increasing acceptance and eventually is promoted to the rank of a theory: A theory is a set of scientific assumptions consistent with one another and ed by evidence, but not fully proved e.g. theory of evolution Thus a biologist studies a problem in a sequential manner through observations, questions, hypothesis, deduction, testing or experimentation. A set of data taken from experiment, proves or disproves the hypothesis. A cautious attitude expressed in the form of criticism and further tests are performed until a satisfactory answer is obtained. The results of observations and experiments are published in scientific journals or presented in conferences, where they can be examined by all. These results must be repeatable that is they should be obtained by any one doing the same procedure.

1.6 HISTORY OF BIOLOGY The history of biology goes back to the ancient and pre historic time. Very briefly, perhaps the first noticeable development in our knowledge of biology occurred during the Greek period. Individual like Aristotle (322-384 B.C) is ed even today. He wrote a book "Historia Animalia". Carolus Linnaeus founder of biological classification, classified animals into two units i.e. genus and species. The Phrastus, discovered sex in plants and described about five hundred plants therefore, known as founder of Botany. Hardly any original addition to biological knowledge was made by the Romans, who followed the Greeks. It was not until the beginning of the Muslim period, nearly a thousand years later that revolutionary developments occurred not only in biology but in the science in general. From the 8th to the 15th century, Muslims studied Greek and other literature, translated books of Roman and Sanskrit into Arabic, wrote new books and opened numerous centers of learning which encouraged original research and exchange of ideas between different human societies. The most outstanding contribution of Muslim scientists had been the use of experiments for the first time in scientific study. This period was truly a period of progress in biology and medicine. The following is a modest list of contributions by the Muslim and other scientists between the 8th and 20th century. Muslim and other Biologists: Muslims have made important contributions in the field of biology in earlier ages. Jabir-Bin-Hayan (722-817 A.D), wrote books named "Al-Nabatat" and "AlHaywan" on plants and animals respectively.


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Abdul Malik Asmai (741 A.D), wrote books "Alkheil, Al-IbiL "Al-wahoosh", "AsSha" and "khalaqul Insan", describing structure and function of body parts of horses, camels, sheep, wild animals and human being. "Khalaqul Insan" was popular among the western experts in Zoology. He was regarded a specialist of his time. Ali bin Rabban Tubri (775-870 A.D), wrote book "Firdus-ul-Hikma" having many illustrations and detailed articles on Philosophy, Zoology, Psychology and Astronomy. Abu-Usman Umer Aljahiz, wrote book "Al-Haywan" which characteristics of 350 species of animals especially, about life of ants.

described

Al-Farabi (870-950 A.D) and Abul-Qasim Al-Zahravi (936-1004 A.D). Both were the renowned hakim and surgeon of the Islamic World. Al Farabi is the author of two very well known books i.e. "Kitab-i-Nabatat" and "Kitab-ul-Haywanat" and Zahravi was famous for the removal of urinary bladder stone. Ibn-al Haitham (965-1039 A.D), wrote books like "Kitabul Manazir" and "Mizanul-Hikma", He explained the phenomenon of vision and corrected the Greek conception about vision. Bu-Ali Sina (980 A.D), wrote books "Al-Qanoon" and "Fil Tib Al-Shifa", about plants, animals and non-living things. He is considered as one of the founder of medicine, acknowledged by the greatest expert of his time in medicines in east and west. Ziauddin Ibn-Baitar (13th century A.D) specialized in the study of plants. He travelled to several countries, observed and studied many species of plants. Ibn-al Nafees (13th century A.D) described the process of blood circulation in human body. Kamal-ud-Din al-Damiri (14th century A.D) compiled a book "Hayat-alHaywan" deals with the characteristics of 1000 kinds of animals. Ali bin Isa was a well known eye-specialist of his time and worked on structure, function and the diseases of the eye. He wrote three volumes on this subject in which he described 130 diseases of the eye. Abul Qasim Majreeti is especially known in Europe for his book on animal species. Other Biologists: After 15th century, European and other biologists made important contribution in the field of Biology. William Harvey (1578-1657 A.D), described circulation of blood. Galileo (1610) invented microscope to examine small organisms. Robbert Hook (1665) discovered "cell" the basic unit of living organism. Linnaeus (1707-1778 A.D), developed methods of classification for organisms and gave nomenclature and therefore, called father of taxonomy. Schleiden and Schawann (1839), worked on the detailed structures of plant and animal cell, finally formulated cell theory.


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Louis Pasteur (1822-1895) discovered bacteria as causes of many diseases like Tuberculosis. J.Lister (1860), discovered antiseptics e.g. Iodine and carbolic acid. E. Jennar (1896), discovered method of vaccination against small pox. Charles Darwin (1859), wrote his famous book "origin of species" about evolution of different species through Natural selection. Gregor John Mendal (1822-1884) gave his famous laws of heredity and laid foundation of Genetics. Watson and Crick (1953) proposed double helix model of DNA to explain the function of DNA as heredity material. 1.7 IMPACT OP BIOLOGICAL STUDIES ON HUMAN WELFARE Biology has made an enormous impact on human welfare by improving quality of life. It also helped in increasing food production and to improve health. New discoveries in the field of biology are bringing revolution in medicine, public health, agriculture, dentistry, veterinary medicine, animal husbandry, land-scape, horticulture, pest control and other related fields. 1.7.1 Production of food: Production of various kind of food especially crops like wheat, maize, rice and barely is very active field of biology. Man grew different vegetables and fruits to supplement his diet. With the advancement of biological techniques man has not only improved the quality and yield of the existing varieties but also produced many new varieties of crops. These successes have been achieved due to biological researches in the fields of pest control, genetics and biotechnology. Man also improved the quality and quantity of food products by developing dairy farming, poultry farming, kettle farming etc, and wheat, rice, maize and other plants. This helped to overcome the problem of food shortage. Incidence of famine has declined and economic conditions for mankind have improved. 1.7.2 Improvement of health: In the field of health, the discovery and development of new medicines, vaccines and diagnostic medical equipment has been very helpful to man kind. This is only possible due to research in biology. The discovery and development of antibiotics by biologist has played a vital role in improving our general health conditions. Many fatal and epidemic diseases such as smallpox, tetanus, diphtheria etc. can be easily controlled because of" development of vaccines against these diseases. This has resulted in a great reduction in infant mortality. Every day new drugs are constantly being developed by biologists to fight against the pathogenic organism enabling to solve the health problems of mankind. 1.7.3 Improvement of environment: During the past few decades, rapid industrialization has resulted in pollution of surroundings including air, land and water sources. As a result of this pollution not only human beings but also animal and plant life is exposed to all kinds of harmful effects. It is through biological research that we are finding out ways and means to overcome and at last eliminate the pollutants, for providing and maintaining healthy environment. 1.7.4 Genetic engineering: A new methodology referred to as recombinant DNA technology or genetic engineering has been developed. It is technique in which alteration of gene, DNA of an organism is carried out to seek benefit for mankind. It provides a way by


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which mammalian proteins can be produced in bacterial cells. Genes controlling the synthesis of important drugs and hormones can be taken from the organisms in which they occur naturally and placed in bacterium or other type of organism, from which the product can be recovered conveniently and in large quantities. Most noteworthy achievement is insulin production by adding human gene in bacterial DNA which is helping to produce human insulin (Humalin) from bacteria on commercial basis. This is very useful for treating diabetes. This is one example along with many others like cloning, tissue culture etc, where genetic engineering is being used. Many inheritable diseases can now be diagnosed in a developing child before birth. Recent research has led to the hope that cystic fibrosis (hereditary disease of human being in which affected individual secrete thick mucus that clogs the air ways of lungs / liver / pancreas) and other hereditary disease will soon be treatable. Although there are many side effects of these technologies yet no one of us wishes to go back to the days in which large number of people died of epidemic diseases. As science has conquered one disease after another, the world's death rate has fallen and the human population has exploded. Few of us are willing to give up technology's gift of private automobile, though we are concerned about the amount of air pollution that automobile generate.

1.8

ORIGIN OF LIFE

1.8.1 Islamic view about the Origin of life: The Holy Quran throws adequate light on the origin of life. The most important fact in the teachings of Quran is that Allah is the ultimate creator of every thing. Living and non-living are both created by Him. There are several verses of Quran in this regard. A few are quoted below: "He is the Creator of the heavens and the earth". (Surah Al'Ana'm, Ayah 102} "That is Allah your Lord. There is no god but Him, the Creator of all things. Therefore, serve Him. He is the Guardian of all things". (Surah Al-Ana'm, Ayah 103) The preceding verse explains that all living beings including insects and snakes (which crawl), monkeys and grazers (four legged creatures) and birds and humans (two legged creatures) were created ultimately from water. It is stated: "We did create man from an essence of clay". (Surah Al-mominoon, Ayah 12) "He (Allah) who created all things in the best way. He first created man from clay, then bred his offspring from a drop of paltry fluid. He then moulded him and breathed into him of His spirit. He gave your eyes and ears, and hearts: yet you are seldom thankful". (Surah Al-Sajda, Ayah 7-9} Once the life had been created, Allah implemented the process of reproduction for the continuity of races of animals. The various stages of reproduction have been described in Holy Quran in following way. "Then fashioned we the drop a clot, then fashioned we the clot a little lump, then fashioned we the little lump bones, then clothed the bones with flesh".


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(Surah Al-mominoon, Ayah 14) "Hath there come upon man (every) any period of time in which he was a thing uned?" (Surah Al-Dahar, Ayah 1) A close study of above sermons reveals that all animals had common origin but they gradually underwent changes afterwards and became different from each other i.e. some developed crawling, some started walking on two legs and some other had four. It seemed that animals of today are advanced forms of the past animals who achieved this form after ing through many changes. 1.8.2 Concepts of Abiogenesis and Biogenesis: Man had believed since ancient times that living organisms (both plants and animals) arise from clay, earth and other non-living matter not from pre-existing parents of their own kind. This was based on such observations as growth of fungus on pieces of bread and the appearance of maggots on dead bodies of animals. Aristotle believed that fishes, frogs and aquatic insects spontaneously developed from mud. This old belief that living beings can spontaneously develop from the non-living is termed as abiogenesis. The idea of production of living from the non-living was experimentally analyzed. The pioneer in such experiments was an Italian scientist named Redi. Through several experiments he showed that all living organisms arise from their parents and negated the idea of abiogenesis. The view that living beings can develop only from other living being is called biogenesis. The following are a few of the experiments which Redi performed and which led to the concept of biogenesis. Experiment No.1 Some dead snakes were placed in a box. It was noticed that flies gathered around the dead snakes. After three days maggots appeared in their bodies. After about eighteen days these maggots transformed into pupae. Some of these pupae were then transferred to separated glass containers covered with a sheet of paper. After eight days, a fly emerged from each pupa and all flies were similar to those which visited the body of the dead snakes. From this it was concluded that maggots were the offspring’s of flies. The flies had laid eggs on the dead snakes. These eggs gave rise to maggots which formed pupae and ultimately flies emerged from them. Experiment No.2 In another experiment Redi took eight bottles. He put dead snakes in two; pieces of meat in other bottle and dead fishes in other bottle. He kept four bottles open and four covered. After a few days, maggots appeared in the open bottles only. No maggots appeared in the bottles kept covered. This showed that if the flies were prevented from entering the bottles, the maggots did not appear. Some workers, however, criticized this experiment and said that the maggots failed to appear in the covered bottles because air being so essential for abiogenesis could not enter these bottles. To test this, Redi performed another experiment. Experiment No.3 Some pieces of meat were put in a bottle whose mouth was covered with a gauze. Thus, air could enter the bottle while flies remained out. Again no maggots appeared on the piece of meat, even after many days inspite of the fact that entry of air was possible.


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These experiments provide evidence ing the idea that only living beings give rise to living beings. Thus, the concept of Biogenesis is correct and that of Abiogenesis is wrong. Needham's experiment: In 1748, an English Scientist Needham, boiled meat in water, poured this gravy in bottles and closed their mouth with cork. After a few days many microorganisms were produced in these covered bottles. This once again excited the believers of Abiogenesis i.e. life from non-life (Fig: 1.3). Pasture's experiment: The argument on the issue of biogenesis and abiogenesis continued up to the middle of nineteenth century, till Louis Pasture, a renowned French scientist proved with experiments, that abiogenesis could not occur in the present environment of earth. In 1864, Pasture performed his experiment, in front of the commission formed of noted biologists, to resolve this issue. He took flasks which had long curved Sshaped necks (Fig. 1.4). He added fermentable infusion (yeast + sugar + water) in bottles and left their mouth open. The yeast infusions were boiled in the flasks and let steam released out of the neck of each flask. Then flasks were allowed to cool. No life was produced even after the lapse of several days; because micro-organisms entering along with incoming air got stuck up in on the curved walls of the glass neck. To prove this he broke up the curved necks, so that now contaminated air could reach directly to the infusion. It was observed that micro-organisms were produced within 48 hours. This proved that if care was taken and no micro-organisms or their spores were allowed to reach the infusion, no life could be produced. He rejected spontaneous generation. Commission decided in favour of bio-genesis. 1.8.3 Concept of chemical and organic evolutional The modern view of origin of life stresses upon the idea of chemical evolution and ties its origin to the history of the earth and the primitive atmosphere. How did it happen and what evidence s this idea? In the beginning, the universe was an intensely hot point where matter and energy were indistinguishable. About 15 billion year ago, there was a Big Bang (huge explosion). The universe started expanding and the temperature dropped drastically. In time, about 4.6 billion years ago our earth and other planets appeared as part of the solar system. The Primitive atmosphere of the earth was rich in Hydrogen. Soon gases from the very hot and liquid core of the earth added more elements to this atmosphere. It is believed that the earth's atmosphere at this stage consisted carbon monoxide, carbon dioxide, Hydrogen, Nitrogen, water vapours and was exposed to intense radiation and electric spark. It hardly had any free oxygen. With the age of time, the atmospheric temperature gradually dropped. This allowed condensation and heavy rains which caused formation of oceans. Thunder and lightning sparks together with ultraviolet radiation caused reactions of the atmospheric gases. This led to formation of simple organic molecules. These molecules I came down with rain and accumulated in the oceans, lakes, rivers and the soil over a very long period of time. These molecules had enough chances to interact in this environment and produce amino acids and proteins which are the building blocks of life. This sequence of chemical evolution was demonstrated in the middle of the 20th century by some clever laboratory experiments. Scientists were able to produce amino acids and simple sugars from a mixture of methane, ammonia, hydrogen and water by exposing it to electric sparks. More recent experiments using electric sparks in laboratory chambers have successfully produced not only amino acids and sugar but also the basic ingredients of fatty substances and DNA, all of which are the constituents of life.


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Life originated on earth more than 3.5 billion years ago. We do not know how life formed, although the evidence is consistent with the hypothesis that it evolved spontaneously from chemicals. There is considerable discussion among biologists about what the early stages of such an evolutionary process might have been like.

What was the first life form like? The first life form, perhaps, was a sphere of naked protein or RNA and was capable of making its copies (reproduction). At some stage, a membrane assembled around the sphere giving rise to the first cell. There is now general agreement that this first life form respired anaerobically because the earth's atmosphere lacked free oxygen; it reproduced asexually. Our present day knowledge of viruses, bacteria and how DNA makes its copies provide enough hints in of the above view. The first living organism may have been like viruses. The next step in this story was appearance of an autotrophic way of life, that is, an organism capable of photosynthesis, adding free oxygen into the atmosphere. This availability of free oxygen opened the way for an explosion of a variety of organisms in times to come. Further improvement became possible as some of the organisms achieved the capability, to reproduce sexually. For at least the first 2 billion years of life on earth, all organisms were bacteria. About 1.5 billion years ago, the first eukaryotes appeared.

The story of origin of life highlights change in matter. First inorganic molecules interacted in a way that organic molecules came into existence. The latter formed aggregates capable of making their copies and existed as naked spheres of protein or nucleic acids (RNA or DNA). Ultimately there arose the first cell a unit with a membrane. This tells us that life eventually arose by a slow process of chemical changes or organic evolution. The basic underlying concept in this process is that over a period of time (a very long period) one form gave rise to another. The idea of organic evolution was ed by scientist like Lamarck and Charles Darwin. They argued that new forms of life must have arisen from older ones through variations and that it was something in the process of heredity which was responsible for variations.


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SUMMARY Biology is the study of living things. It is further divided into three main branches Botany, Zoology and Microbiology. Biology can be divided further into a large number of branches like morphology, anatomy, histology, cytology, physiology ecology, embryology, taxonomy, genetics, paleontology, biochemistry, biotechnology, etc. Biology and other natural and social sciences like chemistry, physics, mathematics, sociology and statistics are inter-related. The systematic process used in resolving a biological problem is called a biological method. Biological investigation starts with observations and collection of information about the biological problems. Hypothesis is a guess made by scientist about the solution of a certain phenomenon. Deduction is a logical explanation of hypothesis. Experiment is the practical testing of hypothesis and deduction. New discoveries in the field of biology are bringing revolution in the fields of medicine, public health, agriculture, veterinary, landscape etc. The old discarded belief that the living beings can spontaneously develop from the non-living is termed as abiogenesis, and the view that only living things can produce their own kind is called biogenesis. Modern view of origin of life stresses upon the idea of chemical evolution and ties it with the origin of earth and the primitive atmosphere. Living organisms had a common origin but, with the age of time, they gradually changed and became different from one another.


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EXERCISE 1.

Fill in the blanks with appropriate : i) ii) iii) iv) v)

2.

Write whether the statements are true or false: i) ii) iii) iv) v)

3.

ii) iii)

iv)

v)

Biology is the study of (a) Life (b) Non-living things (c) Space (d) Earth Study of structure, function and composition of cell is called (a) Cell-Biology (b) Histology (c) Anatomy (d) Genetic Engineering Developmental biology deals with the (a) Growth of organism (b) Functions performed by an organism (c) Development of groups and classes (d) Changes occurring in zygote The intelligent guess of a scientist in the form of a statement is called. (a) Deduction (b) Theory (c) Hypothesis (d) Law Alkheil, Al-Ibil, Al-wahoosh were written by (a) Jabir-Bin-Hayan (b) Abdul Malik Asmai (c) Ibn-al-Haitham (d) Zia-uddin Baitar

Write detailed answers of the following questions: iv) Make a chart to show the steps of a scientific method. ii) iii) iv) v)

5.

Galileo discovered the first microscope. Origin of species is written by Charles Darwin. Study of tiny organism like virus, bacteria, etc is called parasitology. The living things spontaneously develop from mud and clay. Redi was the pioneer scientist who gave the idea of biogenesis.

Encircle the appropriate answer: i)

4.

Linnaeus developed method of _________ for organisms. considered as one of the founder of ________ was medicine. Biology also provides information about relation of existing organism with ______ organism. Sound waves, laser technology and use of radio-active isotopes shows relationship of biology with _______. ______ the deduction and finally the hypothesis.

Write an essay on the contributions of various scientists in the field of biology. Name some branches of biology. Also describe the relationship of biology with other branches of science. What do you mean by biogenesis and abiogenesis? Also give some experiments which explain the concept of biogenesis. Write an essay on origin of life.

Define the following : i) Physiology ii)


Biochemistry

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iii) v) 6.

Observation iv) Genetic Engineering vi)

Deduction Biogenesis

Distinguish between in tabulated form: i) Biogenesis and abiogenesis ii) Hypothesis and theory.


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Chapter 2 STRUCTURAL ORGANIZATION OF LIFE The cell is the basic unit of life. It is the smallest entity in which the life can exist. All the things that living organism can do are done by its cells. In fact some living things are made up of only one cell. Each cell gets food for energy, obtains oxygen, produces energy, gets rid of wastes, maintains homeostasis and produces new cells. How are all these life activities carried out? The answer can be found by examining the composition and working of its parts. Learning objectives:               

Cell as a basic unit of living organism. Discovery of cell and cell theory. Concepts of light microscopy and electron microscopy. Microscopic and Ultramicroscopic structure of plant and animal cells. Structure and functions of different cell structures. Concept of Prokaryotic and Eukaryotic cells and their differences. Reproduction of cell, different methods. Mitosis and Meiosis and their significances. Three level of organization in living organism i.e. tissues, organs and system. Types of plant tissues, simple and compound tissues, their further classification and function in different parts of plant body. Types of animal tissues, epithelial, connective, muscle and nervous tissues, structure of these in relation to their function. Unicellular organization, Amoeba a unicellular organism. Multicellular organization. Brassica as multicellular organization, with root, stem, leaf, flower, fruit and seed as their parts. Frog as multicellular organization with digestive, respiratory, circulatory, excretory, nervous and reproductive organs and systems.

Cell is as fundamental to biology as an atom is to chemistry. All organisms are made of cells, which behave as basic unit of their structure and function. The contraction of muscle cells moves your eyes as you read this book; when you decide to turn this page, nerve cells will transmit that decision from your brain to the muscle cells of your hand so every thing performed by organism is fundamentally occurring at the cellular level. 2.1 DISCOVERY OF CELL AND CELL THEORY In early classes we have studied that all living organisms are composed of cells. The question arises here how did biologist come to know that, obviously through observations. These observations started with the discovery of magnifying glasses and later on with the development of microscope. (Latin word micro = small; skopion = to see). In 1610 Galileo, an Italian astronomer and physicist developed microscope to observe small organisms. In 1665, Robert Hook made an improved microscope by combining lenses, called compound microscope and examined a slice of cork under it. He found small honey comb like chambers, which reminded him small rooms of monastery and are said cellula in Italian, so he also named these structures as cellulae or cell (small rooms). The cork was made from bark of oak, so he actually saw the cell-wall only. in 1842, Dutrochet, boiled plant material in nitric acid and then examined under microscope. It was found to consists of cells. In 1831, Robert Brown discovered a spherical body, the nucleus in the cells of orchids. Schleiden (1838) a German botanist, proposed that all plants are made up of cells. Next year another German Zoologist, Theoder Schwann stated that all animals are made up of cells. He


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observed nuclei in all types of animal cells but failed to observe cell-wall in them. From here the difference between plant and animal cell started to establish. In 1858, Rudolf Virchow stated that new cells come only from other cells i.e animals cells come from animal cell and plant cells from plant cell. The combined efforts of Schleiden, Schwann and R.Virchow finally gave rise to cell theory. The salient features of the cell theory are as under: i) ii) iii)

All living organisms are composed of one or more cells. The cell is the smallest, basic structural and functional unit of all organisms. New cells are formed by the division of pre-existing cells.

2.2 LIGHT MICROSCOPY AND ELECTRON MICROSCOPY The evolution of biology as well as science often parallels the invention of instruments that extend human senses to new limits. The discovery and early study of cells progressed with the invention and improvement of visual instrument, like microscope. Microscopes of various types are still important tools for the study of cells. Resolution  Resolution is the capacity to separate adjacent objects.  Resolution is maintained upto certain magnification.  Resolution improves as the wave length of illumination become shorter.

Magnification  Magnification is a means of increasing size of the object.  By increasing magnification resolution is disturbed.  Magnification improves with the focal length of lens.

The microscopes first used by scientist, as well as the microscope you use in the biology laboratory are light microscopes. These microscope use visible light as the source of illumination and glass lenses for magnification. These lenses reflect the light in a way that the image of the specimen is magnified as it is projected into the human eye. The light microscope can magnify the object upto 1000 times but its resolving power is very limited, i.e just 0.2µm (Resolving power is a measure of the clarity of the image). In 1935, a new type of power full microscope called Electron microscope was invented by scientist to improve the resolving power of microscope. It uses a beam of electron as a source of illumination. The electron beam increases its resolving power. Modern electron microscope can achieve a resolution of about 0.2 nm, a thousand times improvement over light microscope. The electron microscope uses electromagnet as lenses instead of glass lenses. This image cannot focus in human eye, therefore screen or photographic plates are used to review and focus these images. Units of measurement 1 centimeter (cm) = 10-2 meter. 1 millimeter (mm) - 10-3 meter. 1 micrometer (µm) =10-6 meter. 1 nanometer (nm) = 10-9 meter. Electron microscopes reveals many organelles that are impossible to be seen with the light microscope. But the light microscope has many advantages especially for the study of live cells. In electron microscopy, chemicals and physical methods are used to prepare sample which kills cells.


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2.3 BASIC STRUCTURE OF CELL Cells are of different shapes and size according to their functions. inspite of variation found in their shape, all cells basically share many structures in common like cell membrane, cytoplasm, nucleus, etc. In plant cell, cell-membrane is surrounded by a cell-wall. 2.3.1 Cell - Structural and Functional unit: Microscopic studies reveal that all living organisms are composed of cells. Therefore, cell is a unit of structure of living organisms. Cells are of different shapes and sizes, as they have to perform different functions. All basic functional activities, characteristic of living things, occur in the cell. Therefore, cell is also a unit of function of all living organisms. 1. Cell-wall: Cell-wall is the non living, outermost boundary of plant cells, bacterial cells and fungal cells. It is not found in animal cell. It is secreted by the protoplasm of the plant cell. In plant cell it is mainly composed of cellulose and pectin. Ultra microscopic structure of cell-wall shows that cellulose make the fibers which are arranged in criss cross manner. These fibers are kept in their position by a cementing material called calcium pectate (Pectin). Bacterial cell-wall is made up of protein and carbohydrate while fungal cell wall is made up of fungal cellulose and chitin. Thickness of cell-wall varies in different cells of plant. It is composed of three main layers: middle lamella, primary wall, secondary wall and some times tertiary wall. Middle lamella is formed between the primary walls of neighbouring cells. Primary wall, the first wall of plant cell is chemically composed of cellulose and pectin, some limes, lignin. Cell-wall provides protection and to the cell. It gives a definite shape to the cell. It also performs the function of transport of material from outside to inside or vice versa, therefore, it is permeable in nature. 2. Cell- membrane: The cell-membrane or plasma membrane surrounds nucleus and cytoplasm in all types of cells. However in bacteria and plants, plasma membrane itself is surrounded by a cell-wall. It can repair itself to some extent. Different models have been presented to understand the structure of cell membrane. The most acceptable model among them is Fluid mosaic model presented by Singer and Nicholson (1972). According to it, cell membrane consists of lipid (Phospho-lipid) bilayer, in which protein molecules float like iceberg in the sea. This basic structure is found in all the membranes of mitochondria, chloroplast etc. Therefore, it is also called unit membrane. Cell membrane is a selectively permeable membrane because it regulates selective movement of molecules. In many animal cells the cell membrane infolds, taking in materials in the form of vacuoles. This process is called endocytosis. 3. Nucleus or Karyon: Nucleus (discovered by Robert Brown in 1831) is an important arid prominent structure present inside the cell. It controls all the activities of cell. It may be spherical or irregular in shape. In animal cell it is usually present in the center but in plant cell, due to presence of large vacuole it is pushed towards cellmembrane. Nucleus is enveloped by a double membrane called nuclearmembrane. This membrane possesses large number of nuclear pores. Nucleus is filled with a gel like substance called nucleoplasm. The nucleoplasm contains nucleoli and a network of thread like structures called chromatin network. The threads of chromatin become prominent during cell-division. Each thread is called chromosome. These structures of major importance. They are composed of Deoxyribo nucleic acid (DNA) and protein. DNA plays significant role in the


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inheritance of characters as well as in controlling or regulating the cell activities. The number of chromosomes in the cells of all individual of the same species always remains constant. Cells of organism Man Frog Chimpanzee Drosophila (fruit fly) Onion Potato Garden pea

No. of Chromosomes 46 26 48 08 16 48 14

4. Cytoplasm: It is the translucent fluid portion of the cell lying in between plasma membrane and nucleus. It consists of an aqueous ground substance called cytosol and granular portion called cytoplasmic organelles. Chemically cytoplasm is about 90% water and forms a solution and serves as store house of vital chemicals. It is a site of metabolic reactions like protein synthesis, glycolysis etc. Many reactions can occur at the same time in different regions of the cytoplasm. Some important cytoplasmic organelles found in eukaryotic cells. 1. 3. 5. 7.

Endoplasmic reticulum Mitochondria Centrioles Vacuoles

2. 4. 6.

Golgi complex Plastids Ribosomes

1. Endoplasmic reticulum: (Endo= inside, plasma = protoplasm, reticulum=net work). It is a network of membranous channels or tubules extending throughout the cytoplasm. The channels seem to be in with plasma membrane as well as nuclear membrane. There are two types of endoplasmic reticulum. i) Rough endoplasmic reticulum having ribosomes at its outer surface which are involved in protein synthesis. ii) Smooth endoplasmic reticulum without ribosome. Endoplasmic reticulum plays important role in the synthesis and transport of material within the cell. It also provides mechanical to the cell so that its shape is maintained. It detoxifies the harmful effects of drugs. 2. Golgi complex: They were discovered by Camillo Golgi and thus called Golgi complex or bodies or apparatus". They are set of smooth membranes that are stacked into flattened, fluid filled sacs or vesicles containing carbohydrate, glycoproteins and enzymes. Golgi bodies are mainly concerned with the cell secretions. 3. Mitochondria (Sing; mitochondrion): They are generally rod-like or bean shaped organelles consisting of double membrane. The inner membrane is folded. These infoldings are called cristae while the fluid present inside is called matrix. Mitochondria contain enzymes which break the food for the production of energy. As producers of energy they are called Power house of the cell. The number of mitochondria in cell relates to its activities. 4. Plastids:


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Plastids are found in the cells of all the higher plants. These are the organelles which contain different types of pigments. Plastids are of three types on the basis of their pigment or colour (Fig: 2.11) i) Chloroplasts have green pigment i.e. chlorophyll found in leaves and other green parts of a plant. They manufacture carbohydrates by the process of photosynthesis. ii) Chromoplast have coloured pigments other than green found in fruit, flower, petals and other coloured parts of plants . iii) Leucoplast (leucos = white or colourless) are colourless, found in the cells of underground parts of plants. They store food in the form of starch. 5. Centrosome and Centrioles: A rounded structure, the centrosome is present near the nucleus in animal cells. A centrosome contains two centrioles (Fig: 2.12). Each centriole consists of a cylindrical array of 9 rows of microtubules. They form fibrous protein spindle which help in movement of chromosomes towards poles during animal cell division. 6. Ribosome: They are granules, rich in ribonucleic acid (RNA). They serve as sites where proteins are synthesized hence called protein factories of cell. They are found free in cytoplasm as well as attached on the surface of rough endoplasmic reticulum. 7. Vacuole: They are the fluid (other than cytoplasm) filled sacs surrounded by a membrane called tonoplast. In animal cell they are numerous, small but temporary structures while in plant cell they are permanent and very large in size, one or a few in number. They are concerned with storage of cell sap. 2.4 PROKARYOTIC AND EUKARYOTIC CELL There are two types of cells, Prokaryotic and eukaryotic cells. Prokaryotes have prokaryotic cell while eukaryotes have eukaryotic cells. Prokaryotic (pro: before; karyon: nucleus) cell does not possess true nucleus. It means its nuclear material is not enclosed in a proper nuclear membrane. These types of cells are found in bacteria and cyanobacteria (blue green algae). Such organisms are called prokaryotic organisms. Eukaryotic (eu: true, karyon: nucleus) cell possesses proper nucleus where nuclear material is enclosed in a proper nuclear membrane. Plants and animals are composed of this type of cells and are called eukaryotic organisms. Followings are the differences found between them.

1. 2.

3. 4. 5. 6.

Prokaryotic cell Nuclear membrane is absent therefore prokaryotic cells do not possess distinct nucleus. They do not have many of the membrane bound structures e.g. mitochondria E.R, Golgi apparatus etc. Ribosomes are of small size and freely scattered in cytoplasm. Nucleoplasm is absent. Single chromosome is found. Respiratory enzymes are located on the inner surface of the cell


1. 2.

3. 4. 5. 6.

Eukaryotic cell A double nuclear membrane is present. They have well defined nucleus. They have membrane bounded structures (organelles). Ribosomes are of large size and present either on endoplasmic reticulum or free in cytoplasm. Nucleoplasm is present Proper chromosomes in diploid numbers are present. Respiratory enzymes are

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7.

8.


membrane. These cells are simple and comparatively smaller in size i.e. average 0.5 -l0nm in diameter. Bacteria and cyanobacteria are examples of prokaryotes.

7.

8.

present in mitochondria. These cells are complex and comparatively larger in size i.e. 10l00nm in diameter average. Fungi, algae, animal and plants are examples of eukaryotes.

2.5 CELL DIVISION Cells reproduce and increase in number by division. After growing to a certain maximum size, a cell may undergo the process of cell division. During this process the nucleus divides first. This is followed by division of the cytoplasm. This nuclear division is called Karyokinesis (karyon=nucleus; kinesis = division) while the cytoplasmic division is called Cytokinesis. Thus two daughter cells arise from a single division of a cell. There are two main types of cell division found in living organisms. (1) Mitosis

(2) Meiosis

1. Mitosis: In this type of cell division a parent cell divides into two daughter cells in a way that the number of chromosomes in the daughter cells remains the same as in the parent cell. Although mitosis is a continuous process, its karyokinesis can be divided for convenience into four phases which are Prophase, Metaphase, Anaphase and Telophase. Let us now study mitosis is an animal cell. i)

ii)

iii)

iv)

Prophase: During early prophase chromatin material condenses and becomes visible as thick coiled, thread like structures called chromosomes. Each chromosome at this stage is already double, i.e. consists of two chromatids. The chromatids are attached to each other at centromere. The nuclear membrane gradually disappears and at the same time centrosome divides to form two centrioles, each moves towards the opposite pole of the cell and forms the spindle fibres. The centrioles are absent in plant cells. Metaphase: During this phase each chromosome arranges itself on the equator of the spindle. Each chromosome is attached to separate spindle fibre by its centromere. Anaphase: In this phase the centromere of a chromosome divides and the chromatids of each chromosome separates from each other and begin to move towards opposite poles. In this way one set of the chromatids (each chromatid is now an independent chromosome) move towards one pole while the other set towards the other pole. Telophase: This is a stage when the chromatids (now called chromosomes) reach the poles and their movement ceases. Each pole receives the same number of chromosomes as were present in the parent cell. The nuclear membrane is reformed around each set of chromosomes. In this way two daughter nuclei are formed in each cell. Soon the cytoplasm of the cell also divides and two daughter cells arise. The nucleus of each daughter cell contains the same


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chromosome number as in their parent cell. In this way the daughter cells are exact copies of their parent cell. Significance of mitosis: Mitosis plays an important role in the life of an organism. It is responsible for development and growth of organisms by increasing exact copies of cells. With few exceptions all kinds of asexual reproduction and vegetative propagation take place by mitosis. The production of new somatic cells, such as blood cells depends on mitosis. The healing of wounds, repair of wear and tear within organism is also dependent upon the mitotic division. 2. Meiosis: Meiosis or reduction cell-division is a special type of cell-division S| which a parent cell finally divides into four daughter cells in a way that the number of chromosome in each daughter cell reduce to half of their parent cell. Thus it is the reduction of the diploid (2n) number of chromosomes to the haploid (n) number. In animals meiosis produces gametes (sperms and eggs) while in plants it gives rise to spores. The process of meiosis involves two consecutive divisions. (a) Meiosis I - First meiotic division or reduction phase (b) Meiosis II - Second meiotic division or meiotic mitotic phase (a) Meiosis I - First meiotic division or Reduction Phase: This division consists of the following phases. i)

ii)

iii) iv)

Prophase I: Those chromosomes in the cell which 'are similar to each other in shape and size are called homologous chromosomes. Homologous chromosomes occur in pairs. The difference between mitosis and meiosis starts at this point. In mitosis individual chromosomes remain separate from each other while in meiosis the homologous chromosomes come together and form pairs. In each homologous pair, there are four chromatids, since each member (chromosome) of the pair has already doubled itself. Homologous chromosomes to exchange their parts at certain places. This exchange is called crossing over. During crossing over exchange of genetic material takes place and new combination of genes result. The nuclear membrane disappears and at the same time spindle fibres are formed. Metaphase I: During this phase pairs of homologous chromosomes arrange themselves on the equator of the spindle. Unlike mitosis, it is the homologous pair and not the individual chromosomes which attach at separate fibre of the spindle. Anaphase I: The of the homologous pairs now begin to separate and move towards the opposite poles. Telophase I: In this phase the chromosomes come to rest at the poles. The nuclear membranes are reformed around each set of chromosomes resulting in formation of two daughter nuclei. On completion of nuclear division, the cytoplasm also divides and two daughter cells are formed. Each daughter cell has half (haploid) the number of chromosomes present in the parent cell (compared with the cell in prophase) .Thus, the first meiotic division reduces the 2n (diploid-2 sets) chromosomes to n (haploid-half or one set).

(b) Meiosis II - Second meiotic division or Equational Division: During second meiotic division the details are almost similar to those seen in mitosis. During prophase, spindles are formed and the nuclear membrane


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disappears. In metaphase, the chromosomes (each consisting of two chromatids) arrange themselves on the equator. Their chromatids separate from each other in anaphase and migrate to the opposite poles. In telophase, the nuclear membrane reappears around each set of chromatids (now called chromosomes) and the cytoplasm divides forming two daughter cells. So at the end of meiosis four daughter cells are produced in total, each possessing a haploid nucleus. Thus meiosis produces cells (gametes or spores) with a haploid number of chromosomes. Significance of meiosis: Meiosis plays very important role in keeping chromosome number constant in a species from generation to generation. When the haploid male gamete (sperm) fertilizes i.e. fuses with the haploid female gamete (ovum) to form a zygote, the diploid number of chromosomes is restored (n + n = 2n). Meiosis is responsible for genetic variability i.e. the individuals of a given species differ from one another. It is due to crossing over which takes place during prophase I. This genetic variability provides the basis of evolution by providing raw material for it. 2.6 ORGANIZATION OP CELLS TO FORM TISSUES, ORGANS AND ORGAN SYSTEM So far you have learnt about the cell as the basic structural and functional unit of life. The question now is how can a cell express itself as an independent living thing? You know that some small organisms (Amoeba) are made of only one cell These organisms are called unicellular organisms. They represent single cells capable of independent existence by making use of their organelles. Once capable of independent existence, the cell has become an organism. Such an organism represents the unicellular level of organization of life. In some cases, cells have come together to form loose assemblies and live together as a colony. In others, cell with similar structure and function have formed groups. Both have laid down the foundation of multicellular level of organization of life. 2.6.1 Tissues: A major step in the direction of multicellular organization of life has been the formation of tissues. A tissue consists of a group of cells which are similar in structure and function. Both plants and animals tissues have achieved increasing complexity by formation of organs and organ systems. 1. Plant tissues: In plants there are two basic types of tissues which are as follows. i) Meristematic tissue: This tissue contains cells which have ability to divide, so that the number of cells increases and the organism can grow . Meristematic cells are smaller in size with comparatively thin walls and a nucleus in the center. This tissue is commonly present in root tips and shoot apex and helps to increase the length of the root and the shoot by adding primary tissue. ii) Permanent tissue: Permanent tissue is formed from meristematic cells. This tissue is different from meristematic tissue because its cells do not divide. The walls of these cells are thick enabling them to maintain their shape. Permanent tissue may be classified into two groups i.e. simple tissue and complex tissue. Simple tissue is made up of one type of cells forming a homogeneous or uniform mass and a complex tissue is made up of more than one type of cells working together as a unit. a) Simple tissue: Simple tissues may further be divided into following type on the basis of their structure, i.e. Parenchyma, Collenchyma and Sclerenchyma.


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i.

Parenchyma: It consists of living cells which are more or less equally expanded on all sides. These cells have intercellular spaces. They are present in all the soft parts of plant. It is food storing tissue. ii. Collenchyma: It consists of some what elongated cells with the corners filled with cellulose and pectin. Collenchyma occurs in a few layers under the epidermis of herbaceous dicotyledons. iii. Sclerenchyma: Sclerenchyma (scleros =hard) consist of very long, narrow thick walled and lignified cells. They are dead cells. They become hard by deposition of chemical like lignin and thus provide to the plants. They are found in xylem and hard fruit coats etc. b) Complex or Compound tissues: Compound tissues are mainly of two types: (a) Xylem (b) Phloem. These will be discussed later under conducting tissues. Types of permanent tissues on the basis of function: i) Epidermal tissues: The cells of these tissues are rectangular in shape. These tissues form the outer layer of root, stem and leaf .The cells in it are very compactly arranged so that there is no space between them. However, in the stem and leaves, pores called stomata are present through which gases are exchanged. These tissues protect the inner parts of plant. ii) Ground tissues: Ground tissues are composed of thin walled parenchymatous cells, which axe formed from meristematic tissue. These cells are basically meant for storing food. These tissues are present in all parts of the plant except the epidermal and the vascular tissues. iii) ing tissues: When cells reach a maximum size their cell wails become thick due to deposition of special material and become dead. Such cells make up ing tissue. This tissue is of various shapes and provides rigidity and to the plant. Sclerenchyma (thick walled, lignified and elongated) and collenchyma (living cells with thick cellular walls with few small intercellular spaces) are examples of the ing tissues. iv) Conducting or Vascular tissues: These tissues consist of elongated cells with thick or thin walls. Xylem and Phloem are examples of this tissue. The xylem consists of sclerenchyma vessels and fibers, which conducts water and salts from the soil to the leaves and also provides . The phloem is made up of living cells like sieve tubes, which conducts food from leaves to various parts of the plants. Xylem and phloem together form vascular bundle in the stem while they remain separate from each other in the roots. 2. Animal tissues: Like plants, animals have tissues which form organs and organ system. Some important types of animal tissues are: i)

ii)

Epithelial tissue: The cells of this tissue occur in a single layer and are closely packed together. This tissue forms surface layer under lines of the tubular organs of the body. Epithelial tissue occurs in glands where it is variously folded. Connective tissues: These tissues provide to other tissues and organs and bind them together. They consist of a ground substance, cells and fibres. They range from soft to very hard tissues. Fatty tissues are examples of the soft type. Cartilage and bone are special types of these tissues and are hard. Blood is also a special connective tissue with cells suspended in a fluid medium. It transports materials in the body.


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iii) iv)


Muscular tissues: This tissue is formed of muscle fibres. Each muscle fibre is an elongated cell, which has the ability to contract and relax. These tissues are responsible for movement of the body and body parts. Nervous tissues: These tissues are formed of cells called neurons or nerve cells. Nerve cells are specialized to conduct messages in the form of electrical currents. The nervous system (brain, spinal cord, nerves) is made up of this tissue. '

2.6.2 Organs: Your arm is an organ because it consists of various kinds of tissues such as epithelial tissue, muscular tissue, connective tissue and nervous tissue. All of these tissues have come together in the arm to make it an organ. Your heart, kidney, liver and many others structures are organs made in the same way. Similarly, in a plant the root, the stem and the leaves arc organs. The stem, for example, consists of several tissues such as epidermal tissue, ground tissue and conducting tissue. 2.6.3 Organ systems: Organs work together as a unit to perform a particular function to make an organ system. For example, the digestive system is made of organs such as mouth, gut, liver and pancreas are all working together to digest food. There are other systems in the animal body such as transport, respiratory, excretory, muscle, skeletal, nervous and reproductive systems. In plants also, the tissues and organs (root, stem, and leaves) are organized to form systems. However, the systems, here are not so clearly organized as in the animals. It is usual to study these in plants, as conduction, storage, ing systems, or root and shoot systems. In this chapter you are studying life at various levels of organization from the simplest to the most complex. A simple diagram of this organization is given below: Cells Tissues Organs  Systems  Organism 2.7 UNICELLULAR ORGANISMS Those animals and plants, which are single-celled, are called unicellular organisms. Amoeba is one of the example. Amoeba: It is a unicellular aquatic organism found in stagnant water pools and ponds. It is microscopic in size measuring about 0.25 millimeter. It does not possess a permanent form and' keeps on changing its shape. The structure of Amoeba is very simple. The nucleus and cytoplasm are surrounded by a protective cell membrane. Cytoplasm is differentiated into two parts. Its outer portion, which is clear and transparent is called ectoplasm. The inner viscous, translucent and granular part is called endoplasm. The endoplasm contains many food vacuoles of different size, a contractile vacuole and other cells organelles. Nucleus is usually present in the centre but as the Amoeba moves, the nucleus changes its position. The contractile vacuole functions to remove excess water from the body. The food vacuoles contain food particles. The animal moves by producing temporary finger-like projections called pseudopodia (Pseudo = false, podia a feet). The pseudopodia are also used to capture food particles, which enter the body as food vacuoles. Amoeba respires by exchanging gases with the surrounding water through its surface. 2.8

MULTICELLULARORGANISMS


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The majority of living organisms consist of many cells and are called multicellular organisms. Brassica and frog have been selected here as representative examples of multicellular plants and animals, respectively. 2.8.1 Brassica: Brassica campestris is the botanical name of mustard (sarsoun). You are very familiar with this plant since its oil (mustard oil) is used for cooking and its leaves are used as vegetable (saag). Structure of Brassica: This plant consists of roots, stem, leaves, flowers, fruit and seeds. These parts can be divided into two categories on functional basis i.e. vegetative parts and reproductive parts. The vegetative parts are those which do not directly take part in sexual reproduction. These parts are root, stem, branches and leaves. The reproductive parts consist of sex organs which are directly related to sexual reproduction. These are flowers. 1.

Vegetative parts: i) Root: The root is that part, which grows under the soil and develops from the radicle of the seed. The first part of the root to arise from the radicle is known as the primary root. During its growth it gives off secondary and tertiary roots. The primary roots are thicker than the secondary and tertiary roots. The tips of all the roots bear a cap, the root cap. The root bears fine, thin root hairs. The plant absorbs water and minerals from the soil through the root hairs only, the rest of the root fix the plant to the soil.

Internal structure: The outer part of a root is the epidermis (epi=above; derma=skin), which protects the root. Root hairs are outgrowths of epidermal cells. Next to epidermis is the cortex. Cortex is composed of parenchyma cells. Parenchyma cells store food material. Within the cortex is a central cylinder region called the stele. The stele of the root is surrounded on the outside by a layer of cells called endodermis. Next to the endodermis is a layer of cells called pericycle. Branch of the root originate from the pericycle. The central part of the stele is occupied by a star shaped xylem. In between the arms of the xylem is phloem. Rest of the stele is made of parenchyma cells. ii) Stem: This part of plant develops from the plumule of the seed and grows away from the soil. It bears branches and flowers. The point, on the stem or on a branch, which gives rise to leaf, is known as the node. The part between two adjacent nodes is called the internode. The stem and the branches transport water and salts from the root to the leaves. It also transports prepared food from the leaves to all parts of the plant. In addition, the stem s the leaves and the branches in the air, thus enabling the leaves to receive maximum amount of sun light for photosynthesis. The stem and its branches also bear flowers, which are the reproductive organs. Internal structure: A cross section of Brassica stem shows that it is surrounded on the outside by a single layered epidermis. Next to the epidermis is cortex. The cortex is made up of parenchyma and collenchyma cells. Food material is stored in the cortex. Next to the cortex is a ring of vascular bundles. Each bundle consists of xylem and phloem. Xylem is located towards the inside and phloem towards the outside. In between xylem and phloem, there is a region consisting of meristematic cells


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called cambium. The centre of the stem is occupied by pith. It is made up of parenchyma cells and stores food material. iii) Leaf: Leaves grow out on the stem and its branches from the nodes. Generally, the leaf of Brassica consists of two parts. The lower stalk like part is the petiole and upper green expanded portion is the lamina. Young leaves are without petioles and their margins are entire or smooth but in mature leaves the margin is wavy. There is a swollen vein in the middle of the leaf which is known as midrib. The branch veins emerge and spread in the leaf like a net. These veins are actually vascular bundles consisting of xylem and phloem. This network of veins s the leaf and keeps its lamina in an expanded position. New branches of the plant arise from buds present in the axil of the leaf. The function of the leaf is to prepare food. Therefore, all of its tissues are arranged in such a way that photosynthesis can take place easily.----------------------------------------The leaves are arranged on the stem and branches in such a way that their upper surfaces remain directly exposed to sunlight while the lower surface does not get the same amount of light. Due to this difference the upper and lower surfaces are slightly different from each other. Leaves having different upper and lower surfaces are called bifacial leaves. Internal structure: A leaf is composed of several distinct cell layers. The upper layer of a leaf is called the upper epidermis. The lower layer of the leaf is called the lower epidermis, which contains stomata (Sing: Stoma). Each stoma has a pore and two guard cells. The tissue between upper and lower epidermis is called the mesophyll. The mesophyll cells below the upper epidermis are longer than broad and are closely packed. It is called the palisade layer. The cells next to the palisade layer are irregular in shape and loosely arranged having spaces like sponge and is called the spongy layer. Photosynthesis takes place in palisade and spongy mesophylls. Running through the leaf are many vascular bundles or veins. The veins are composed of xylem and phloem. Xylem is located towards the upper side and the phloem towards the lower epidermis. 2. Reproductive parts Flower: With growing age, Brassica plant bears small, yellowish flowers. Flowers are the most beautiful and important parts of the plant. They are arranged on young branches in a special way. This special arrangement of the flowers on the stem is called inflorescence. Parts of the flower: The flower in Brassica is situated on a stalk known as pedicel. The tip of the pedicel bears thalamus. The floral leaves are arranged in four whorls on the thalamus. These whorls, starting from the outermost to the central one, are in the following order. i)

ii)

Calyx: This is the outermost whorl and consists of four free sepals. The sepals are light greenish in young flowers but as the flower matures, their colour also becomes yellowish like that of the petals. The most important function of the calyx is to cover the inner parts of the flower and to protect them from sunlight and rain. Corolla: This is the second whorl and is composed of four free yellow petals. Because of the petals, the flower becomes very conspicuous that honey bees, butterflies and other insects are easily attracted and thus help in pollination.


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iii)

iv)


Androecium: The androecium lies inside the petals. It makes the third whorl of the floral leaves. Its parts are not leaf-like. The androecium consists of six free stamens which are the male reproductive organs of the flower. In Brassica flower, the stamens are arranged in two circles. The outer circle has two small stamens. The inner circle has four long stamens. Each stamen has two well defined parts, a lower delicate stalk called the filament and an upper swollen part called the anther. Each anther contains numerous pollen grains. When the anther matures a longitudinal slit in its wall enables the pollen grains to escape. There are dark green nectaries of small size at the base of the androecium. These nectaries contain nectar (a honey-like substance). This nectar is the food of insects. When the insects are attracted towards the flowers to collect this nectar pollen grains get attached to their bodies and are transferred from one flower to another. This results in the pollination of flowers. Gynoecium: This is fourth whorl occupying the central position in the flower. The parts of the gynoecium are called carpels, who are the female reproductive organs of the plant. In Brassica, gynoecium is formed by the union of two carpels. Each carpel is divisible into three main parts. The lower swollen part is the ovary. Above the ovary carpel extends into a thin stalk, the style. The style has swollen tip, which is called stigma. In the ovary many ovules are present, which ripen into seeds. The ovary ripens and is converted into fruit. The fruit of Brassica is a long dry capsule with many seeds. The seeds are very small and light. They can be easily dispersed by air currents. When these seeds fall on a suitable place they germinate and produce new Brassica plants.

2.8.2 Frog: The frog lives both in water as well as on land. It swims in water and moves by jumping when on land. There is a membranous skin between its toes which helps in swimming. There are five toes in each foot but the hand has only four fingers because the thumb is rudimentary. In male frog the first finger is thicker than the others. Frog has neither a neck nor a tail. As the head is directly attached to the trunk frog cannot move it as we can. The conical head has two large bulging eyes. Behind each eye is a circular area called tympanic membrane. These membranes help in hearing. At the tip of the snout it has two openings called external nostrils by which frog breathes. The skin of the frog is loose and slippery. It is slippery due to secretions produced by glands present in it. Frogs are found in abundance in the rainy season during which they lay eggs. They hibernate during the winter season by burying themselves in the mud and stay there throughout the winter. This phenomenon is called hibernation or winter sleep. Internal organs: The internal organs are located in the body cavity, which is also called coelom. These organs make up various systems, which perform specific functions. These are as follows: 1. Digestive system: The organs involved in the breakdown of complex food into simpler form (digestion) constitute the digestive system. This system is composed of a tube, the alimentary canal and special glands associated with it. The alimentary canal consists of buccal cavity, pharynx, oesophagus, stomach and intestine. i) Buccal cavity: Food enters into the buccal cavity through mouth. The upper jaw has a row of weak but pointed teeth. They are not meant for chewing food but prevent it from slipping out of the mouth. The tongue of frog is unique in being attached in front to the floor of


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ii)

iii)

iv)

v)


the buccal cavity and being free behind. This allows the animal to throw it outward.---------------------------------------------------------Frog feeds mainly on insects. On seeing the prey, it suddenly throws out its tongue. The prey sticks to its sticky tongue. The tongue is then immediately withdrawn and the prey is swallowed. Pharynx: The buccal cavity opens into a short but narrow pharynx, which leads into a wide tube,, the oesophagus. Immediately behind the tongue on the floor of the pharynx is a slit like opening, the glottis, which opens into the lungs. When the food es into the oesophagus, the glottis is closed and during respiration it is opened. Oesophagus and stomach: Pharynx opens into a wide tube called oesophagus or gullet; It transports food into the stomach. Stomach is a thick walled, muscular and glandular sac. Anterior end of stomach is called cardiac end while posterior end is called pyloric end. Food is grounded in stomach and mixed with enzyme pepsin, which partially digest proteins. Food in stomach changes into a paste like substance called chyme. Intestine: The intestine is a long narrow coiled tube. It is divisible into small and a large intestine. The partially digested food from the stomach enters the small intestine through pyloric end, where its digestion is completed. The digested food is absorbed into blood. The undigestible parts of the food enter the large intestine, also called rectum. The short terminal part of rectum is called cloaca. From cloaca undigested food is expelled out as faeces through its opening called cloacal aperture. This is a common aperture for urine, reproductive and undigested food discharge. Liver and pancreas: The liver is a large reddish-brown gland located adjacent to the stomach. Its secretion is known as bile. Between the lobes of the liver is a rounded pouch called gall bladder, which stores bile. A bile duct arises from it. On its way, this duct es through pancreas and s the pancreatic duct. The pancreas lies between stomach and duodenum, the first part of small intestine. Its secretion, pancreatic juice, is carried by the pancreatic duct. The pancreatic duct and the bile duct to form a common hepato-pancreatic duct, which then opens into duodenum. The bile and the pancreatic juice help in the complete digestion of the food in the small intestine.-------------------------------------------Digestion is a process by which the complex insoluble food substances are converted into soluble form by the action of enzymes. The digested food is then absorbed into the blood through the intestinal walls.

2. Respiratory system: Energy is required by every organism to carry on all the life activities. It is produced by the oxidation of food specially glucose. This process takes place in the cells. For oxidation the cells require oxygen and as a result of oxidation of food they produce CO2 as waste product. This entire process called respiration, divided into two phases. a) b)

Gaseous exchange or Extra-cellular respiration Cellular respiration.

We will restrict our discussion upto gaseous exchange as respiration. Frog has three types of respiration on the basis of organs involved in the gaseous exchange. These are: i)

Pulmonary respiration


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ii) ii)

Cutaneous respiration Buccal respiration

i)

Pulmonary respiration:---------------------------------------------------The gaseous exchange, which takes place in lungs is called pulmonary respiration. The frog has two lungs, which are balloon like structures. Their outer surface is smooth but their inner surface has numerous folds which increase the area for gaseous exchange. The lungs are richly supplied with blood vessels. Each lung has a bronchus at its upper end. The two bronchi open into a larynx. The glottis opens into the larynx.------------------------During respiration air is taken in by the external nostrils. It es into the buccal cavity through the internal nostrils. From here it enters the glottis, es through the larynx and bronchi finally reach the lungs. In the lungs, exchange of gases between air and blood takes place i.e. oxygen is taken up by the blood and CO2 is given out, which leaves the body through same route. Aresting

ii)

iii)

human

breathes out

about

500

litres

of

CO2

every 24 hours.

Cutaneous respiration:---------------------------------------------------Gaseous exchange carried out by skin, is called cutaneous respiration. Frog uses skin as a respiratory organ during swimming and hibernation. Oxygen diffuse into blood through skin while CO2 diffuses out from the network blood capillaries in skin. Buccal respiration:--------------------------------------------------------The lining of buccal cavity is thin, moist and richly supplied with blood capillaries. Here also exchange of gases takes place between the air and blood. This type of respiration is called buccal respiration.

3. Circulatory system: Every cell requires a supply of oxygen and nutrient molecules and must get rid of waste products. For this purpose a transport system usually called circulatory system is required. Blood transports these materials during its circulation through out the body. Frog has a closed type circulatory system in which blood circulates in the closed circuit of blood vessels being pumped by an organ called heart, This system is also called cardiovascular system. It consists of: i) ii)

Heart- strong muscular pumping organ. Three kinds of blood vessels: (a) Arteries － Which carry blood away from heart. (b) Veins － Which return blood to the heart. (c) Capillaries － Exchange material between tissues and blood.

Heart: Heart is a conical, muscular pumping organ, located in the anterior region of body cavity. It is enclosed in a membrane called pericardium. It contracts and expands continuously through out the life. This contraction and expansion of heart is called heart beat, due to which blood circulates continuously in the body. Frog heart consists of three chambers. (i) (ii) (iii)

Right auricle or Atrium. Left auricle or Atrium. Ventricle.

The longest heart stoppage was 4 hours. A Norwegian fell into the sea in December 1987.


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Survival was due to the low temperature of his body in the sea.

The truncus arteriosus originates from ventral side of the ventricle and divide into two branches each of which divides into three arches (arteries). Another thin walled triangular sac called sinus venosus formed by major veins opens into right atrium. Both of these structures are not true chambers of heart but often called accessory chambers. In heart, the flow of blood is continuous and moves in two path ways. The oxygenated blood from the lungs enters the left auricle through pulmonary veins. The deoxygenated blood from all other parts of the body enters the sinus venosus. From sinus venosus, it reaches the right auricle. When the two auricles contract, the blood is pushed into the single ventricle. When ventricle contracts it is pumped into the truncus arteriosus From here it enter (a) the pulmonary arteries, which carry the blood to lungs for oxygenation and (b) the systemic arteries, which supply it to all parts.pf the body and (c) the carotid arteries, which supply it to the brain. A human being contains about 70 ml of blood per Kilogram of body weight. For an adult, this is about 4 or 5 liters.

The opening between various chambers of the heart are guarded by valves, which prevent the flow of blood in reverse direction. 4. Arterial system: A blood vessel, which carries blood away from heart to the various body parts is called an artery. The arterial system can be simply stated to comprise of the following three main components. Pulmocutaneous arteries: They supply deoxygenated blood to lungs and skin where it gives up carbon dioxide and picks up oxygen. Carotid arteries: These vessels arise from the truncus arteriosus, and supply the oxygenated blood to various parts of the head region such as brain, tongue, head muscles, eyes, ears etc. Systemic arteries: These vessels carry oxygenated blood to all the parts of the body except the head and lungs. They fuse together to form a major vessel of this system called aorta, which gives off branches to various parts of the body such as fore and hind limbs, digestive system, liver, pancreas, kidneys, genital organs and muscles. 5. Venous system: It is a set of blood vessel, called veins, which bring the blood from all the parts of the body towards heart. The venous system consists of the following major components. (i)

The oxygenated blood from the lungs is collected by pulmonary veins, which bring it to the left auricle of the heart. (ii) The deoxygenated blood from head and fore limbs is collected through several veins, which together to form one major precaval vein, on each side. (iii) Blood from all the lower parts of the body such as stomach, intestine, liver, pancreas, genital organs, muscles, hind limbs etc, is collected through veins, which together and form one major vein called post caval. Both the pre-cavals and the post-caval open into the sinus venosus from where the blood is pumped into the right auricle of the heart.


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Portal system: Set of veins, which collect the blood from one organ and discharge it into another organ, is called portal veins. The set of veins draining their blood into liver are included in hepatic portal whereas the set opening into the kidneys are called renal portal system. Hepatic portal system: The veins collecting the blood from the digestive system do not carry it directly to the heart. They all to form a hepatic portal vein, which breaks up into capillaries in the liver to allow transfer of some of the digested food into the liver for storage. From the liver, blood enters the postcaval, which carries it to the sinus venosus. Some of the blood from hind limbs is collected in an abdominal vein, which s the hepatic portal vein in the liver and drains blood into liver from where it is collected by the post caval vein. These veins are also included hepatic portal system. Renal portal system: The alternate route of blood from the hind limbs is by the way of a renal portal vein. These veins begin in capillaries in the hind limbs and breaks up into capillaries in the kidneys. From the kidneys, this blood enters the post caval by renal veins and ultimately returns to the heart. These veins arc included in renal portal system. 6. Excretory system: It is the set of organs involved in the process of excretion i.e. the removal of metabolic waste matters from the body. This function is performed by kidneys, which filter out the excretory matter from the blood and it out in the form of urine. There are two kidneys in frog. They are elongated reddish brown organs attached to the dorsal wall of the body cavity. The urine is carried from the kidneys by a pair of tubes called ureters, which open into the cloaca. From the cloaca, it is either ed out directly through cloacal aperture or is stored for some time in a bag, the urinary bladder. 7. Reproductive system: Reproduction is the process of production of new babies by their parents. Organs involved in this process are included in reproductive system. Sexes are separate in the frog. The reproductive organs consist of gonads and their ducts. The gonads produce germ cells and the ducts them but of the body. The male gonad is known as the testis (plural testes) and the female gonad is called the ovary. The gonads are paired structures and are located near the kidneys. The sex cell of male is sperm and that of female is ovum (Plural ova) or egg. The ova are released into water through the cloaca in the mating season. The male produces sperms during the breeding season. Sperms are also released from the testes into water near the eggs. Each sperm fuses with a egg and a new frog starts developing. 8. Nervous system: The set of organs, which control and co-ordinate all the activities of the body is called nervous system. It is composed of two parts, i.e the central nervous system and the peripheral nervous system. The central nervous system includes the brain and the spinal cord whereas the peripheral nervous system comprises of nerves, which connect the central nervous system with various parts of the body, i.e. muscles, glands and sense organs. The animal with the heaviest brain is the sperm whale. Its brain weighs about 9.2 Kg.

The brain is protected in the skull and the spinal cord is enclosed in the vertebral column. The brain consists of the following regions: (i) The most anterior region comprises the olfactory lobes.


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(ii)

Immediately behind the olfactory lobes, there are two large outgrowths called the cerebral hemispheres. (iii) Behind the hemispheres are located two prominent outgrowths called the optic lobes. (iv) The part between the optic lobes and hemispheres is known as the diencephalon. On the dorsal surface of diencephalon is present a pineal body while the pituitary gland is attached to its ventral surface. (v) The last part of the brain consists of the cerebellum and the medulla oblongata. The spinal cord starts from the posterior end of the medulla oblongata like a thick thread. It es from the skull through a hole and enters the canal of the vertebral column. The vertebral column protects the spinal cord just as the skull protects the brain. Brain and spinal cord are not solid. They have a system of canals which is filled with a fluid. Olfactory lobes are associated with the sense of smell and transfer of olfactory sensation to the cerebral hemispheres, which are the seats of intelligence and memory. The diencephalon receives a variety of messages from the internal and external environment of the body and also controls the secretion of hormones from the pituitary gland. The optic lobes are associated with the eyes and vision. The cerebellum and the medulla oblongata co-ordinate body movements and maintain balance of the body. The medulla also controls respiration, circulation and digestion. The spinal cord controls the movements of the trunk area, and many other functions independently. The peripheral system connects body parts with the central nervous system. This system consists of cranial and spinal nerves. Cranial nerves connect and establish communication between various parts of brain and parts of the head while the spinal nerves connect structures of the trunk area with the spinal cord. Some special nerves are present in the head and trunk region called the autonomic nerves, which work automatically. Autonomic nerves control the internal organs of the body such as heart, lungs, stomach, smooth muscles of the intestine, vessels and glands. 2.9 SENSE ORGANS To get the informations about the environment organisms like frog have receptor organs. These receptors send sensations to the central nervous system via nerves. The frog has many types of receptors. Its skin has many small microscopic receptors for the sense of touch. For smell, there are olfactory receptor located in the nostrils. For the sense of taste sensory cells are present in taste buds on the tongue. Ears are used for receiving sound waves and maintaining balancing and eyes for receiving light i.e. sight. The animal with the most acute sense of smell is the male emperor moth. Using its antennae, it can detect a female emperor moth 11.Km upwind The biggest mammalian tongue that has ever been weighed belonged to a Blue whale caught by Russian trawlers in 1947. Its tongue weighed 4.3 tonnes.

1. Ear: In frog, like the other vertebrates, the organ of hearing is the ear. Its outer most part is the tympanic membrane. An external ear called pinna is absent in frog. On the inner side of this membrane is a cavity known as tympanic cavity. The cavity contains three small rod- like bones called ossicles Its one end is attached to the tympanic membrane and the other with the internal ear.


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High pitched sounds are rapid vibrations of the molecules In air. Human can hear sounds which vibrate at about 19 KHz. Some bats can hear ultrasonic sounds upto about 160 KHz.

The internal ear (Fig: 2.43) is a very delicate organ. It consists of three semicircular canals. These canals are filled with a fluid and sensory cells are located at special places in these canals. When sound waves strike the tympanic membrane it is set into vibration. This vibrates ossicles which in turn, vibrate the internal ear and thus, sound waves stimulate the hearing receptors in the inner ear. The internal ear, in addition to hearing, also keeps the balance of the body. 2. Eye: The frog has two eyes one on each side of the head (Fig: 2.44). If we make vertical section of the eye, we find that the innermost layer of the ball is the sensory retina. The retina contains photoreceptor cells. Outside the retina is the choroid, which is richly supplied with blood capillaries supplying nutrients to the retina. The sclerotic is the hard, outer most layer of the eye. It provides shape to the eye ball. The anterior transparent part of the eye is called cornea. Behind the cornea is iris. The iris has a window called the pupil. Behind the pupil is the lens of the eye. The cornea, pupil and lens focus light on the retina. A watery fluid is present in between the cornea and lens. Similarly a jelly like fluid is present between the lens and retina, through which light es before it strikes retina. Optic nerve takes the sensory messages from the eye to the brain.


36

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SUMMARY     



 





 



 

Cell is the basic unit of living organisms. All the living organisms are made up of one or more cell. Cells are observed under light and electron microscopic. Resolution power of electron microscope is very much high. Plant cell consist of cell-wall, cell membrane, cytoplasm and nucleus, in an animal cell all these parts are present except cell-wall. Prokaryotic cell is the type of cell with out proper nucleus while eukaryotic cell contains proper membrane bound nucleus. Cell wall is non-living part of cell, mainly composed of cellulose and pectin. Cell membrane is a thin, differentially permeable membrane which limits the cytoplasm. Translucent material filled in between nucleus and plasma membrane is called cytoplasm. Cytoplasm contains many granular bodies called cytoplasmic organelles like, endoplasmic reticulum, golgi bodies, lysosome, ribosome, mitochondria, plastids etc. Cells divide to increase in numbers. Mitosis is the equational type of cell-division in which chromosome number does not change. Meiosis is the reductional cell-division in which number of chromosomes reduces to half. Tissues are the groups of similar cells. Amoeba is an example of unicellular organization, Brassica and frog of multicellular organization.


37

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1.


EXERCISE Fill in the blanks with appropriate : i) Animals which consist of only one cell are called________ ii) Finger like projection in amoeba are called________ iii) Botanical name of mustard plant is__________ iv) Reproductive part of a higher plant is_______ v) Part of stem from where leaf arises is called

2.

Write whether the following statements are true or false: i) Gonads are the organs responsible to produce germ cells. ii) Brain and spinal cord are the parts of peripheral nervous system. iii) Pulmonary vein contains de-oxygenated blood. iv) Truncus arteriosus and sinus venosus are the true chambers of the heart of frog. v) During pulmonary respiration gaseous exchange takes place through skin.

3.

Encircle the appropriate answer: i) ii) iii) iv) v)

Nucleus of cell was discovered by (a) Robert Hooke (b) Schleiden (c) Robert Brown (d) Virchow The type of lenses of light microscope is (a) Biconcave (b) Convex (c) Concave (d) Electromagnetic DNA is found in (a) Nucleus (b) Chromosome (c) Cell (d) Nucleoplasm Prokaryotic cells do not contain (a) Nucleus (b) Membrane bound nucleus (c) Ribosome (d) Cell-membrane The number of chambers in the heart of frog is (a) Two (b) Three (c) Four (d) Five

4.

Write detailed answers of the following questions: i) Make a chart of different types of plant tissues: ii) Draw a diagram showing different parts of a typical plant cell. iii) Describe those organelles which are only found in plant cell. iv) Describe digestive System of frog with the help of diagram. v) What is the difference between cellular respiration and gaseous exchange? Describe different methods of gaseous exchange in frog. vi) What do you mean by cell-division? Describe the method of celldivision by which gametes or spores are produced.

5. i) ii) iii)

Give scientific reason of the following: Why is cell membrane differentially permeable? Why is cell called the basic structural and functional unit of life?. How do the chromosome number remains the same in the of same species? Why is meiosis called reductional cell-division? Why is upper surface of dicot leaf much darker than the lower surface?

iv) v) 6.

Define the following : i) Cell ii) Tissue iv) Eukaryotic cell v) Chromosomes vii) Connective tissueviii) Meiosis


iii) Prokaryotic cell--------------vi) Mitochondria-----------------ix) Meristematic tissue----------

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x) Compound tissue xi) Mitosis xiii) Neuron or Nerve cells 7.

xii)Hibernation

Distinguish between: i) Prokaryotic and eukaryotic cell. ii) Cell-wall and cell-membrane. iii) Mitochondria and plastids. iv) Light and electron microscope. v) Arteries and veins.


39

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SECTION 3 BIODIVERSITY Around two million types of organisms exist on the earth today; much more have gone extinct, many more are yet to be discovered. To study such a diversified group it is customary to classify it into groups. Two hundred years ago biologists divided all the organisms, into two kingdoms, as either plants or animals. But closer examination with better techniques necessitated three more kingdoms.

Chapter 3 CLASSIFICATION OF LIVING ORGANISMS It is a human instinct to organize various objects into sets. Likewise biologists, rather than dealing with millions of different organisms, classify them into major groups. The science of classifying living organisms is taxonomy. A classification system is based on shared characteristics. General characteristics allow for large grouping of very diverse organisms. More specific characters result in smaller groups. Classification enables biologists to study and identify various organisms more easily. Learning objectives:  The exact meaning of classification.  The advantages of classifying living organisms.  Criteria used in the classification of living organisms.  The units of classification like species, genera, families, orders, classes, phyla/divisions and kingdoms.  Binomial nomenclature.  Common and scientific names of living organisms. 3.1

DEFINITION AND AIMS OF CLASSIFICATION

The scientific study which deals with the classification of living organisms is called taxonomy (Taxis = Arrangement and Nomos = Law) So, taxonomy deals with the laws governing the arrangement or classification of living organisms. In a broader sense, taxonomy can be defined as a branch of biology, which deals with the description, identification, classification and naming of living organisms according to structural similarities and dissimilarities. Technical description means to describe a living organism by using scientific .

3.2

BASIS OF CLASSIFICATION

All the living organisms placed in a particular group have many fundamental similarities in their structure. It is not always easy to recognize these basic similarities. Many bases and techniques are used to classify organism. It is principally the homologous structure that one considers in grouping organisms. Homologous structures are those that are similar because of their common origin. Sometimes it is impossible to classify organisms using morphological criteria, so one may compare the chemical substances which they contain. This is particularly useful when classifying organisms like bacteria which may all look alike and have an identical cellular structure. Other characteristics used in classifying organisms include cytological structures with the help of electron microscope, genetic constitution and their developmental patterns etc.


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3.3


UNITS OF CLASSIFICATION

The basic unit of biological classification is the species. A species is a group of organisms which has numerous physical features in common and which are normally capable of inter breeding and producing fertile offspring. Closely related species are grouped together into genera (singular- genus). Similar genera are grouped together into families, families into Orders, orders into classes, classes into phyla (singular -phylum) or divisions and phyla or divisions into kingdoms. Intermediate categories are also sometimes used; for example a subphylum or sub-division between phylum and class, and sub classes between class and order. The name of a species maybe given on the basis of i) Locality ii) Character of plant in) Religious belief iv) Scientist who first discovered it For example: Ficus bengalensis (Banyan tree) named after locality. Ficus religious (Peepal) named after religious belief. Ficus elastica (Rubber plant) named after that atex is extracted. Ficus erica named after Eric a person.

3.4

BINOMIAL NOMENCLATURE

O. Linnaeus adopted the binomial nomenclature system for naming organisms to eliminate confusion while using native or common names when describing an organism. He gave each species a scientific name comprising two words. This is known as binomial nomenclature. The first name refers to the genus and is called generic name and always begins with a capital letter. The species name follows the generic name and begins with small letter. Scientific name for mustard is Brassica campestris, for frog is Rana tigrina and for human is Homo sapiens. Every scientific name is written in italic or it is underlined. 3.5

COMMON SCIENTIFIC NAMES AND CLASSIFICATION

1)

Common name KINGDOM DIVISION CLASS ORDER FAMILY GENUS SPECIES SCIENTIFIC NAME

… … … … … … … … …

Mustard Plantae Tracheophyta Dicotyledonae Capparales Brassicaceae Brassica Campestris Brasica Campestris

2)

Common name KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES SCIENTIFIC NAME

… … … … … … … … …

Man Animalia Chordata Mammalia Primat Hominidae Homo Sapiens Homo Sapiens


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3)


Common name KINGDOM PHYLUM CLASS ORDER FAMILY GENUAL SPECIES SCIENTIFIC NAME

… … … … … … … … …

Frog Animalia Chordata Amphibia Salientia (Anura) Ranidae Rana Tigrina Ranatigrina

3.6 MAJOR GRQUPS OF LIVING ORGANISMS Two Kingdom to five Kingdom classification: Previously living things were classified into two kingdoms namely Plant Kingdom and Animal Kingdom. The basis of this division was presence or absence of cell-wall and chlorophyll. All the living organisms having cell-wall and chlorophyll were regarded as plants and placed and studied under Kingdom Plantae. All those living organisms having neither cell-wall, nor chlorophyll were regarded as animals and placed and studied under Kingdom Animalia. But a large ruimber of living organisms did not fit cleary into the category of plants and animals. To solve this problem, Robert H. Whittaker (1969) suggested a new system of classifying living organisms. According to this new system there are live kingdoms of living organisms. 1. Kingdom Monera, prokaryotes which feed by a variety of different methods. 2. Kingdom Protista, unicellular eukaryotes which feed by a variety of methods. 3. Kindgdom Fungi, multicellular eukaryotes which feed heterotrophically by absorption. 4. Kingdom Plantae, multicellular eukaryotes which feed photosynthetically. 5. Kingdom Animalia, multicellular eukaryotes which feed heterotrophically by ingestion. Although Whittaker's Scheme received wide spread approval, it had one major draw back. This relates to the protist kingdom, which contained all unicellular organisms, including those that formerly had been regarded, as animal (Protozoan) and those that had been regarded as plant (unicellular algae). Other problem was that it meant putting the algae into two separate kingdoms, the protista and the plant kingdom. This led two other biologists, Margulis and Schwartz, to put forward a modification of Whittaker's scheme (1989). According to this, there are five kingdoms of living organisms as listed below: 1. Kingdom Prokaryotae: It includes all the prokaryotes, e.g. bacteria and cyanobacteria etc. 2. Kingdom Protoctista: It includes all the eukaryotic organisms, which are no longer classified as animals, plants or fungi, e.g. Euglena, Paramecium, Chlamydomonas, yeast etc. 3. Kingdom Fungi: It includes non-chlorophyllous, multicellular, eukaryotic organisms having cell-wall e.g. Agaricus (mushroom) etc. 4. Kingdom Plantae: It includes all the chlorophyllous multicellular eukaryotic living organisms, having cell-wall and embryonic development e.g. Apple, Sunflower etc. 5. Kingdom Animalia: It includes all the non-chlorophyllous multicellular eukaryotic organisms, having no cell-wall, e.g. hydra, earthworm, man etc.


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SUMMARY         

There are uncountable forms of life ranging from VIRUS (border line between the living and non-living) to the most highly evolved and complex life in the form of human-beings. The scientific study which deals with the classification of living organisms is called Taxonomy (Taxis= Arrangement. Nomos=Law). All the living organisms placed in a particular group have many fundamental similarities in their structure. The basic unit of biological classification is the species. Closely related species are grouped together into genera. Each grouping of organisms within the hierarchy is called a taxon (plural taxa) and each taxon has a rank and a name for example class Mammalia or genus Homo. Linnaeus's system of naming give each species a scientific name comprising two words is known as binomial nomenclature. Previously living things were classified into two kingdoms namely plant kingdom and animal kingdom. Now a days living organisms are classified into five kingdoms.


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EXERCISE 1. i) ii) iii)

Fill in the blanks with appropriate : The term biodiversity means variety of ___________. The study which deals with the classification! of living organisms is called __________. The basic unit of biological classification is the __________.

2. i) ii) iii)

Write whether the statements are true or false : Closely related species are grouped together into genera. Closely related genera are grouped together into classes. The plural of taxon is taxa.

3. i)

Encircle the appropriate answer: The family of mustard is (a) Brassicaceae (b) Poaeceae (c) Rosaceae (d) Palmaceae Closely related species are grouped together into (a) Family (b) Genus (c) Order (d) Class Multicellular organisms having no cell-wall and no chlorophyll are (a) Fungi (b) Bacteria (c) Animals (d) Plants

ii) iii)

4. i) ii) iii) 5. i) ii) iii)

Write detailed answers of the following questions: Define taxonomy and describe the aims, bass and units of classification. Name the five kingdoms of living organisms. Write down the differentiating characters and examples of each kingdom. Why is the kingdom protoctista difficult to classify? What is the basis of their grouping in kingdom protoctista? Give examples of each of its group. Write short answers of the following questions: What is the definition of taxonomy? Define species. Write a note on binomial nomenclature.


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Chapter 4 VIRUS, BACTERIA AND CYANOBACTERIA The most abundant organisms on earth are so small that they cannot be seen with the naked eye. They are most successful hence so abundant to be found every where in large numbers. Though structurally simple viruses and bacteria play an important role in the biosphere. Learning objectives:  Micro-organisms, a heterogenous group of living organisms which can only be seen with the help of microscope.  Discovery of virus, characteristics, structure, types and the diseases caused by viruses in humans, other animals and plants.  Characters of bacteria.  Shapes, nutrition and importance of bacteria.  Characters of cyanobacteria. 4.1

MICRO-ORGANISMS — AS A HETEROGENOUS GROUP OF ORGANISMS

The minute living organisms which cannot be seen without the help of microscope are called micro organisms. They form a heterogenous group which includes viruses, bacteria, cyanobacteria, protozoa, unicellular algae and some fungi. Bacteria and cyanobacteria are prokaryotes and studied under kingdom prokaryota (Monera). Rest of the micro-organisms are eukaryotic and studied under protoctista (Protista). Bacteria are heterotroph as well as autotroph, but all of cyanobacteria and algae are autotroph. Protozoa are heterotroph. Viruses lie somewhere between living and nonliving organisms. 4.1.1 Viruses: Viruses (Latin word Viron = Poison) are the smallest, the simplest and perhaps the most primitive living things. By 1800's many biologists had demonstrated that many diseases of man and other organisms were caused by bacteria. Some diseases puzzled them. One such disease was tobacco mosaic disease occurring in tobacco plant leaves. In 1892, Russian biologist, Iwanowsky showed that this disease was due to some thing smaller than bacteria. He named them as viruses. No one had seen them because they were too small to be seen even with the compound microscope. The year 1935 was important in solving the story of what viruses really are and how they behave. A new kind of microscope the electron microscope had been constructed and any object smaller than mµ (millimicron 1,000,000,000th part of a metre) can be observed. Wendell Stanley crystallized the infectious particles, now known as tobacco mosaic virus (TMV). This TMV and many other viruses were actually seen with the help of the electron microscope. 4.1.2 Characteristics: Viruses are non-cellular obligate parasites that always have a protein coat and a nucleic acid core. They cannot live and reproduce outside of living cells since they lack the ability to do so by themselves. They range in size from 20 nm to 250 nm (One nm =10-9 metre). They are sub-microscopic. There is no sexual or asexual reproduction. They reproduce by replication.


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The simple viruses use the enzymes of the host cell for both their protein synthesis and gene replication; the more complex ones contain upto 200 genes and are capable of synthesizing, through their host many structural proteins and enzymes themselves. Viruses are either virulent, destroying the cell in which they occur or temperate, becoming integrated into their host genomes (total hereditary materials) and remaining stable there for long periods of time. 4.1.3 Structure: They appear like small rods, tadpoles 6r may be polyhedrals or like little spheres. Viruses may consist of nucleic acid, capsids, envelopes and tail-fibers. Their nucleic acid may consist of a single or several molecules of DNA or RNA. The smallest viruses have only four genes while the largest have upto two hundreds. The protein coat that encloses the nucleic acid is called a capsid. It may be of different shapes. Capsid is made up of protein subunits called capsomeres. The number of capsomeres is characteristics of a particular virus. Some viruses have accessory structures called viral-envelopes that help them infect their hosts. They are membranes covering their capsids. The simplest viruses consist of a single molecule of a nucleic acid (DNA or RNA) surrounded by a capsid, which is male up of different protein molecules. Some bacterial viruses or bacteriophages, are among the most complex viruses. Each of them is made up of at least five separate proteins: these make up the head; the tail core, the molecules of the capsid, the base plate of the tail, and the tail fibers. A long DNA molecule is coiled within the head. They may be: Plant-viruses Animal-viruses Bacteriophages

infecting plants, infecting animals and which infect bacteria.

4.1.4 Viruses living or non-living: Viruses are considered as living organism because of the following characteristics; 1. Viruses with their core of DNA or RNA surrounded by a protein coat somewhat resemble the chromosomes of other living organisms. 2. They have the ability to reproduce (Property of replication-reproduction). 3. Many kinds of viruses are known to undergo mutations. 4. Viruses show genetic recombination. However, they show following characteristics not exhibited by living organisms. i) Non-cellular structure. ii) Undergo crystallization. iii) Completely inactive outside host's cell. 4.1.5 Viral diseases (Transmission/spread and control) 1.

Animal diseases:

Several of the animal viruses cause many important diseases. Poliomyelitis caused by polio virus was a wide spread, crippling disease. Although poliomyelitis


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is now largely under control by vaccination in the developed countries, it remains a serious and common disease in the tropics and elsewhere in the less developed parts of the world. Colds are viral infections of the upper respiratory tract. More than 200 of viruses that cause colds have been identified. Measles and Mumps are the common viral diseases of children. However, proper vaccination of MMR vaccine develops immunity against these infections. Human Immune Virus (HIV) was discovered in 1985 to be the cause of Acquired Immune Deficiency Syndrome (AIDS). Rabies, in humans is also caused by a virus but flu is the most common disease caused by the influenza virus. The majority of human viral diseases are spread through respiratory tract by air borne droplet spread by sneezing and coughing of infectious people or by the contaminated water and food or by blood or other body fluids. Hygienic living and vaccinations are the two best controls of viral diseases. 2.

Plant diseases:

One of the best known plant disease is caused by tobacco mosaic virus. This virus affects the leaves of tobacco plants and light green and yellow patches appear on the leaves of diseased plant. Agriculturists have not yet succeeded to device cure for most of viral diseases of plants. Therefore, their efforts are focused largely on reducing the incidence and transmission of such diseases and also on developing varieties of crop that are relatively resistant to certain viruses. 4.2

BACTERIA

Bacteria grow in every habitat of earth under all possible environmental conditions. They are the largest number of creatures and are found everywhere. They can survive in freezing temperature and also in hot sulphur springs. Bacteria, first observed by Leeuwenhoek are considered as the smallest, oldest but the simplest living organisms. Bacterial cell ranges in size from 0.2 µ. (micron) to 2 µ in width and 2 to 10 µ (microns) in length. Bacteria are strictly unicellular prokaryotes. Bacterial cell consists of cell-wall, plasma-membrane, cytoplasm and nuclear material. Cell-wall is chemically complex and totally different from ordinary plant cell-wall as cellulose is not present. It is thick and rigid and made up of amino-acids, sugar and sometimes chitin. Next to cell-wall is thin outer most layer of plasma membrane or cell membrane which is attached to cell-wall at few places. It has many pores. Chemically, it is made up of lipids and proteins. Cell-membrane performs the function of respiration as mitochondria are absent in them. It also acts as selective membrane. Cytoplasm is granular, present in between cell-membrane and nuclear region. It has many but small vacuoles, ribosomes and glycogen-particles. It has no endoplasmic reticulum and no other membranous organelles like golgi apparatus, plastid and mitochondria. Bacteria do not possess well organized nucleus as they have no nuclearmembrane, no nucleolus, no nucleoplasm and no structures like typical


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chromosomes. However, DNA is found as concentrated structures called chromatin-bodies. Shortly before a bacterium divides, these DNA bodies replicate (double) and are equally distributed to the daughter cells. Thus, there is no typical mitosis instead they divided by binary fission. 4.2.1 Form (Shapes): There are different shapes of bacteria. i)

Cocci: (Singular-Coccus = Gr. Kokkos = Berry, rounded). They are spherical and according to cell-arrangement they are: Solitary (single) (Monococcus), in pair (Diplococci), in chain (Streptococci), in cluster (Staphylococci) etc.They are non-flagellated.

ii)

Bacilli: (Singular-Bacillus = L, Bakulus = A rod) .They are rod shaped. They may be found in pairs (Diplobacillus) or in chains (Streptobacillus) etc. They may be flagellated.

iii)

Spirilla: (Singular-Spirillum = Gr. Sperira = A coil. They are spiral or cork screw shaped (spirillum).

iv)

Vibrio or comma: They are slightly curved or comma (,) shaped e.g Vibrio cholerae. They may be flagellated.

4.2.2 Nutrition: Most bacteria are heterotrophic with few autotrophic. Heterotrophic bacteria are those which cannot synthesize their organic compounds from simple inorganic substances. According to their mode of feeding, heterotrophic bacteria may be saprophytic, symbiotic or parasitic. i)

Saprophytic bacteria:

They get their food from dead organic matter. The soil is full of organic compounds in the form of humus. Bacteria living in the soil have large number of enzymes that break down the complex substances of humus to simpler compounds. These bacteria absorb and utilize these simple compounds as a source of energy. Many other saprophytic bacteria cause decay of dead animal and plant material as they convert complex organic compounds to simpler ones. ii)

Symbiotic bacteria:

They are found associated with other living organisms. They obtain food from the host without harming it, e.g. nitrogen fixing bacteria in the roots of leguminous plants. iii)

Parasitic bacteria:

They grow inside the tissues of other living organisms and obtain food at the expense of host. These bacteria lack certain complex systems of enzymes. iv)

Autotrophic bacteria:

They can synthesize organic compounds from simple inorganic substances. Autotrophic bacteria may be photosynthetic or chemosynthetic.


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a) Photosynthetic bacteria: They have pigments very similar to the chlorophyll and named as bacterio chlorphyll. These pigments are bounded by invaginated plasma membrane in the cytoplasm and not in the chloroplast. They carry out photosynthesis. The majority of bacteria are free-living heterotrophs (saprophytic decomposers) that contribute significantly to recycling matter through ecosystems. Many are also symbiotic heterotrophs, including those that cause disease. b) Chemosynthetic bacteria: They obtain their energy from oxidation of some inorganic substances like iron, hydrogen, nitrogen and sulphur compounds to synthesize their organic compounds. 4.2.3 Respiration: Another aspect of metabolism which can be used in the classification of bacteria is their need for oxygen in respiration. Aerobes require oxygen for respiration. Anaerobes respire without oxygen. Some bacteria are killed in the presence of oxygen, they are called obligate anaerobes. Others use oxygen but can respire without it, they are called facultative anaerobes. Bacteria which can only survive with oxygen present are obligate aerobes. 4.2.4 Importance of bacteria: 1.

Useful bacteria:

i) Agricultural bacteria: Bacteria decompose dead plants and animals bodies and convert various organic compounds into simple forms such as nitrates, sulphates, phosphates etc for utilization by green plants again. Nitrifying bacteria convert the proteins of these dead bodies into nitrates. Then these nitrates are absorbed and utilized by the green plants. Soil bacteria increase the fertility of the soil by bringing about physical and chemical changes in the soil. ii) Alimentary canal bacteria: They help herbivores in the digestion of cellulose by producing an enzyme Cellulose. Similarly some are present in human beings and make vitamins. iii) Industrial bacteria: They help in curing and ripening of tobacco leaves, fermentation of sugar into alcohol, ripening of cheese, retting (softening) of fibres, curdling of milk, conversion of hides into leather etc. iv) Medicinal bacteria: Valuable antibiotic drugs have been obtained from bacteria, e.g Thyrothycin, Subtilin. Riboflavin is a vitamin produced by Clostridium. 2.

Harmful bacteria:

i) Pathogenic bacteria: They are responsible for most varied kind of diseases in human beings, animals and plants. They may act as invisible enemies for man. Some of the diseases found in man due to bacteria are typhoid, tetanus, cholera, diphtheria, and tuberculosis (T. B) etc. Plant diseases caused by bacteria are black rots of cabbage, citrus canker, fine-blight of pear and apple, ring rot of potato etc.


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ii)


Food spoilage: Bacteria spoil food by fermentation and decomposition.

4.3) CYANOBACTERIA (Blue green algae) Salient features of this group are: 1. 2. 3. 4. 5. 6. 7.

These blue-green algae are Prokaryotic. They may occur alone or in the form of colony. Cell wall is double layered. Protoplasm is differentiated into an outer coloured region—chromoplasm and an inner colourless region—centroplasm. Found in fresh water, few are marine. Total absence of sexual reproduction. Only asexual reproduction takes place e.g. Nostoc, Anabena.

Cyanobacteria are photosynthesizers that sometimes can also fix atmospheric nitrogen. They were probably the first organisms who introduced oxygen into the primitive atmosphere and probably first to colonize land. NOSTOC: Taxonomic position: According to new classification, Nostoc belongs to kingdom prokaryotae(Monera). Structure: The Nostoc is filamentous. The filaments are intermixed in a gelatinous mass forming a ball like structure. It floats on water. A single filament look like a chain of beads. Each filament is unbranched and has a single row of rounded or oval cells. Each cell has double layered wall. The outer thicker layer is made up of cellulose mixed up with pectin. The inner thin layer is made up purely of cellulose. The protoplasm is differentiated into an outer coloured region - chromoplasm and an inner colourless region centroplasm. There is total absence of endoplasmic reticulum, mitochondria, golgi bodies and vacuole. However ribosomes, pseudovacuoles and reserve food are present. The centroplasm also called central body have hereditary material (DNA) in the form of long coiled structure called chromatin body. At interval there are found slightly larger oblong, colourless cells with slightly thicker walls. These are called heterocyst. Each heterocyst is the center of nitrogen fixation. But they are specially concerned with the multiplication of filaments during unfavorable conditions.


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SUMMARY        

 

Living organisms which cannot be seen without the help of microscope are called micro organisms. They form a heterogenous group which includes viruses, bacteria, cyanobacteria, protozoa, unicellular algae and some fungi. Viruses are the smallest, the simplest and perhaps the most primitive living organisms. Viruses are non-cellular parasites. They cannot live and reproduce outside the living cells. Some bacterial viruses or bacteriophages are among the most complex viruses. There are three types of viruses. Plant-viruses infecting plants. Animal-viruses infecting animals. Bacteriophages are those which infect bacteria. Bacteria are the most abundant prokayrotes with variety of shapes. Most bacteria are heterotrophic a few are autotrophic. According to their mode of feeding, heterotrophic bacteria may be saprophytic, symbiotic or parasitic. Some bacteria are killed in the presence of oxygen, they are called obligate anaerobes. Others use oxygen but can respire without it, they are called facultative anaerobes. Bacteria which need oxygen for survival are obligate aerobes. Bacteria are responsible for most varied kind of diseases in human beings, animals and plants. They may act as invisible enemies of man. The Nostoc is filamentous. The filaments are intermixed in a gelatinous mass forming a ball like structure. It floats on water. A single filament look like a chain of beads.


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EXERCISE 1.

Fill in the blanks with appropriate : i) Previously, living organisms were classified into two kingdoms namely Plant Kingdom and ________ kingdom. ii) Whittaker proposed ___________ kingdoms. iii) Kingdom Protista has been renamed as ________ . iv) Kingdom Monera contains all ________ organisms. v) A single filament of Nostoc look like a _______ of beads.

2.

Write whether the statements are false or true: i) Kingdom Protoctista includes all the eukaryotic organisms, which are no longer classified as animals, plants or fungi. ii) Bacteria, cyanobacteria, protozoa are all micro-organisms. iii) Electron microscope was constructed in. the year 1945. iv) Virus mainly consist of capsid and Nucleic acid. v) AIDS is a disease caused by bacteria.

3.

Encircle the appropriate answer: i) Viruses are (a) Cellular (b) Noncellular (c) Multicellular (d) Unicellular ii) Characteristic of viruses due to which they are considered as living. (a) Noncellular structure (b) Total parasite (c) Undergo crystalization (d) Undergo reproduction iii) Bacilli bacteria are (a) Rounded (b) Rod shaped (c) Spiral shaped (d) Curved iv) Streptococci are the bacteria which occur (a) Two in number (b) Four in number (c) In chain (d) In bunch v) Nostoc belongs to (a) Cocci bacteria (b) Eubacteria (c) Cyanobacteria (d) None of them

Write detailed answers of the following questions: i) Discuss in detail the discovery, characteristics, structure and types of viruses. ii) Give the general characters, shapes, nutrition and economic importance of bacteria. Write short answers of the following questions: i) What are the four types of bacteria according to shapes? ii) What do you mean by Industrial bacteria? iii) Name the five Kingdoms proposed by Whittaker. iv) Explain the different autotrophic modes of nutrition in Bacteria. v) Describe salient features of Cyanobacteria.


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Chapter 5 FUNGI AND ALGAE

Algae play an important role in nature. Bearing chlorophyll they produce more oxygen than all the land plants combined. Without the oxygen produced by algae, most of the plants and animals could not survive. Earth around us would have been a mess without the recycling'of the dead and waste matters. Fungi, together with bacteria, are at work everywhere on the earth doing this recycling business. Learning objectives: • Algae and Fungi. • General characters of fungi with reference to Rhizopus, Penicillium, Agaricus, Ustilago. • Importance of fungi. • General characters of algae with reference to Chlamydomonas and Spirogyra. • Economic importance of Algae. 5.1 FUNGI Fungi are a group of living organisms having a body called mycelium, made up of hyphae which are coenocytic (multi nucleated), non-chlorophyllous and have a cell-wall of fungal cellulose. 5.1.1 General characters: According to old concept, fungi were considered as plants and placed in thallophyta but now they have been assigned a separate kingdom the Fungi. Main characteristics are as under: i) They are non-chlorophyllous. ii) Cell-wall is made up of fungal cellulose. iii) They are coenocytic. iv) Fungal body is called mycelium which is made up of thread like cells called hyphae (Sing = Hypha). v) The reserve food is in the form of glycogen-particles and oil-globules. vi) They reproduce asexually by means of spores or by budding or by fragmentation. vii) Sexually, they reproduce by means of conjugation (Isogamy). viii) The mode of nutrition may be saprophytic, parasitic or symbiotic. ix) There are two views about their origin. Either they have evolved from an Alga or from certain unflagellate protozoa. x) The fungi are distinguished amongst themselves primarily by their sexual reproductive structures. Common examples include Yeast, Agaricus, Penicillium, Rhizopus etc. Agaricus (Mushroom): Some species of Agaricus are commonly cultivated as food, for example the button mushroom, Agaricus campestris. An effort is being made to increase the cultivation of additional species of mushrooms, especially in Asia. Some can be grown on waste products. Many have a high protein content, as well as a delicate flavour. Penicillium: Among the other economically important fungi Penicillium is one of the name. Some species of penicillium are sources of the well-known antibiotic penicillin. Other species of the genus give the characteristic flavours and aromas to cheese.


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Ustilago: Another kind of fungi including Ustilago are responsible for the rust and smut diseases of cereals. 5.1.3 Importance of Fungi: Food: A number of edible fungi in the form of mushrooms are a source of nourishing and delicious food-dishes. Today- they are grown as a crop in many places throughout the world. But one must bear in mind that not all the mushrooms are edible. Some of them are poisonous and popularly called as toad stool or death-stool. Yeasts, another kind of fungi, are utilized in baking industry. Others are used in brewing, and in cheese and organic acid producing industries. Medicines: Fungi have opened a new field in medicine being the course of antibiotics like Penicillin, Chloromycetin, Neomycin, Terramycin etc. Soil fertility: They maintain soil fertility by decomposing the dead organic matter. Fermentation: The property of fermentation is utilized for the manufacture of ethanol, organic acids and alcoholic beverages. Saccharomyces cerevisiae (brewer's yeast) synthesizes a range of vitamins of B-group. Food spoilage: Fungi cause tremendous amounts of spoilage of food-stuff by many of the saprophytic fungi. Human diseases: Fungi cause a number of diseases in human beings like aspergillosis (ear and lungs disease), moniliasis (skin, mouth, gums disease), ring worm disease etc. Plant diseases: Fungi destroy many agricultural crops, fruits, ornamentals and other kinds of plants. Some of the diseases are loose-smut of wheat, late-blight of potato, downy and powdery mildews etc. Rusts and smuts can cause crop destruction in large area. Spoilage: Many types of fungi are responsible for the spoilage of leather-goods, wool, books, timber, cotton etc. 5.2

ALGAE

The term algae is used for a large and very diverse group of mainly aquatic autotrophic organisms ranging from single celled (Chlamydomonas) to large multicellular seaweeds (Sargassum). Previously algae were regarded as plants and placed in thallophyta. R.H. Whitaker (1969) placed them in two groups — unicellular eukaryotic algae in Protista and multicellular algae were considered as plant and placed in Kingdom Plantae. Finally all the algae have been placed in Kingdom Protoctista (Margulis and Schwartz). Algae are classified on the basis of the type of pigment they contain; therefore, there are green, golden brown, brown, and red algae. All algae contain green chlorophyll, but they may also contain other pigments that mask the colour of the chlorophyll. Algae are also grouped according to biochemical differences, such as the chemistry of the cell-wall and the chemical compound used to store excess food. Common examples of Algae are Chlamydomonas, Spirogyra, Ulva etc. 1.

Chlamydomonas:


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It is a fresh-water alga. It is found growing in still water of ponds, pools, ditches, tanks, lakes etc. It grows abundantly in polluted water rich in organic matter and ammonium compounds. It is unicellular, eukaryotic green, motile alga. It is spherical, oval or pear-shaped with pointed anterior end. It has cell-wall, cytoplasm, distinct nucleus and two flagella. Cell-wall is thin but firm and transparent. It is made up of cellulose and pectin compounds. Cytoplasm has an outer thin clear region and an inner dense region. Cytoplasm has granular endoplasmic reticulum, free ribosomes, mitochondria, golgi bodies, chloroplast, pyrenoid, contractile vacuoles and an eye-spot. There is a single large cup-shaped chloroplast occupying major part of the cell. It lies towards posterior end. The single protoplasmic body inside chloroplast is pyrenoid. It is a tiny starch manufacturing factory. There are two small contractile vacuoles present towards anterior end and at the base of two flagella. They are pulsating in nature under-going alternate expansipn and contraction. These are considered to regulate water content of the cell. They may be regarded as excretory organelles. Eye-spot is an orange coloured structure. It is situated anterolaterally. This is sensitive to intensity of light. Flagella are the two cytoplasmic elongation arising near the contractile vacuoles. Nucleus is circular and present in the cup-shaped cavity formed by chloroplast. 2. Spirogyra: It is a green fresh water alga, usually found floating freely on slow running streams and stagnant water, rarely attached to substratum by branched rhizoidal cells called holdfast. Spirogyra is unicellular, but grows in colonial form known as filament. The filaments are unbranched and consists of uniform cylindrical cells which are ed end to end. All the cells are alike and there is no differentiation of base and apex in a filament. Each cell is much longer than it is broad. Its outer wall is made up of cellulose and pectin substances. Pectin swells up and forms a gelatinous sheath around whole filament, it also makes the filament slimy The cell has a parietal layer of cytoplasm known as primordial utricle which encloses a large vacuole, filled with cell sap. The chloroplast is ribbon shaped with toothed margin. The number of chloroplast present varies from 1-14 according to species. These chloroplast are spirally arranged in protoplasm Each chloroplast has several rounded bodies along its length, these bodies are made up of protein and are known as pyrenoids. Nucleus is present to some extent in the center of cell, it is suspended by cytoplasmic strands.


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    

 


SUMMARY Fungi is a group of living organisms having a body called mycelium, made up of hyphae which are coenocytic, non-chlorophyllous and have a cellwall. The fungi are distinguished primarily by their sexual reproductive structures. Some species of fungi are commonly cultivated as food for example, the button mushroom. Rusts and smuts are important fungal plant pathogens. Among the economically important genera of fungi are Penicillium and Aspergillus. Some species of Penicillium are sources of the well-known antibiotic penicillin, and other species of the genus give the characteristic flavours and aromas to cheese. The term algae is used for a large and very diverse group of mainly aquatic autotrophic organisms ranging from single celled (Chlamydomonas) to the large multicellular seaweeds (Sargassum). Spirogyra is unicellular, but grows in colonial form known as filament. The filaments are unbranched and consist of uniform cylindrical cells which are ed end to end.


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EXERCISE 1. Fill in the blanks with appropriate : i) The body of a fungus is called ________ . ii) Mycelium of fungi is made up of ________. iii) Yeast belongs to _________group of living organism. iv) Chlamydomonas is a unicellular, ________ alga. v) Rust and smuts of cereal crop is due to _______. 2. Write whether the following statements are true or false: i) Spirogyra is unicellular and colonial. ii) Chlamydomonas is colonial. iii) Sargassum belongs to fungi. iv) Cell-wall of fungus is made up of cellulose. v) Some species of penicillium are source of antibiotic penicillin. 3. i) ii) iii) iv) v)

Encircle the appropriate answer: The characteristic not associated with Fungi (a) Non-chlorophyllous (b) Coenocytic (c) Body called mycelium (d) True cellulose Which is not a fungus? (a) Aspergillus (b) Chlamydomonas (c) Agaricus (d) Saccharomyces Which one is not an alga? (a)Chlorella (b)Volvox (c) Spirogyra (d) Yeast Chloroplast of spirogyra is (a)Ring shaped (b)Cup shaped (c)Ribbon shaped (d) Spherical Agaricus is commonly known as (a) Bread mold (b) Yeast (c) Mushroom (d) All of them

4. Write detailed answers of the following questions: i) Describe general characters of algae and briefly describe an alga. ii) Describe the structure of Spirogyra and Chlamydomonas? iii) Give economic important of fungi. iv) What is fungus? Describe general characters of fungi. v) Discuss the importance of algae and fungi. 5. Define the following : i) Pyrenoid ii) Fungi iii)


Isogamy iv) Mycellium v)Hyphae

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Chapter 06 BRYOPHYTES AND TRACHEOPHYTES

Plants are the connecting link between inorganic and organic world. They are all autotroph and manufacture food for all forms of life hence called producers. The constitute the most important link in ecosystem. Learning objects:        

General characters of Kingdom Plantae. The two groups of plants. General of Bryophytes with reference to Funaria. General of Tracheophytes and their major groups. Study of pteridophyte with reference to Pteris, Adiantum. Characteristic feature of Spermatophyte. Gymnosperms and study of pinus and Thuja. General characters of flowering plants and their different paits. Morphological differences between dicots and monocots.

6.1 BRYOPHYTES (Bryon = a moss; phyton = plant) Bryophytes and tracheophytes are included in Kingdom Plantae. Both have well developed embryos which give rise to their plant bodies. Bryophytes are defined as multicellular, eukaryotic, chlorophyllous, non-vascular plants having cell-wall made up of cellulose and their zygotes develop into an embryo. Plants are multicellular photosynthesizers that are adapted to living on land. AH plants protect their embryos from dessication. 6.1.1 General of Bryophytes: Bryophytes are the simplest group of plants. They are relatively poorly adapted to life on land, so are mainly confined to damp shady places. They are amphibious needing water for sexual reproduction. They have thalloid bodies which are not differentiated into true root, stem and leaves. Instead of roots, they have unicellular hair like structures called rhizoids. Some bryophytes have pseudo stem and leaves. They do not have vascular bundles. All plants have a life cycle that shows an alternation of generations; some have a dominant gametophyte and some have a dominant sporophyte. Bryophytes show distinct heteromorphic alternation of generation. It means the two generations called gametophyte and sporophyte are morphologically as well as cytologically different. In contrast to other plants, bryophytes have main generation gametophyte (Haploid). The gametophyte reproduces sexually by producing dissimilar male and female gametes. These two fuse to form zygote, which develops into well protected embryo. This gives rise to sporophyte, which may be partly or completely dependent on gametophyte. Spores are produced in sporophyte after meiosis. Each spore germinates into a gametophyte. Bryophytes are classified into three groups. 1. Hepaticae (Liverworts) 2. Musci (Mosses) 3. Anthocerotae (Hornwots)


e.g. Marchantia having dicotomously, branched dorsiventral thalloids tructure. e.g. Funaria having rhizoids,stem and leaves. e.g. Anthoceros having horn like capsules.

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Funaria: Gametophyte consists of rhizoids, pseudo stem and leaves. The stem may be branched. Male sex organs called Antheridia (singular-antheridium) are located at the apex of male branch and female sex-organs called archegonia (singular archegonium) at the tip of female branch. Fertilization takes place when plant is submerged in water. Zygote is formed inside archegonium, which develops, into an embryo. Embryo develops into a sporophyte, which remains attached with gametophyte. Sporophyte consists of foot, seta and capsule. The foot is anchored to the gametophyte and absorbs nutrients from it. Seta elevates the capsule in the air. Within capsule spores are formed after meiosis. Due to dehydration, capsule burst open and spores are liberated. Each spore germinates into Funaria gametophyte. 6.2

TRACHBOPHYTES (VASCULAR PLANTS)

6.2.1 General characters: Tracheophyte (Trachea = Vessel; Phyton = Plant) have conducting or vascular tissues. You have already studied that xylem and phloem are types of two conducting tissues which are not only responsible for the conduction of material but also give rigidity and to the plant body. Nearly, all tracheophytes have well developed true root, stem and leaves. They vary greatly in height ranging from miniature to giant size like Sequoia (Red wood tree). All tracheophytes show alternation of generation in which sporophyte generation is dominant and totally independent, whereas gametophyte generation may be very small, inconspicuous, short lived and totally dependent on sporophyte except in pteridophytes. The zygote develops into well protected embryo from which young plant is produced. 6.2.2 Major groups of tracheophytes: Tracheophytes are divided into pteridophytes and spermatophytes. Pteridophytes are non-seed producing plants. They are further divided into psilopsida, lycopsida, sphenopsida and pteropsida. Pteropsida (Ferns) are the common and important group of pteridophyte. They are found growing in nature or in moist cool, shady places. The common examples of ferns are Dryopteris, Pteris, Adiantum, Marsilea etc. In the non seed vascular plants, such as ferns, there is a dominant vascular sporophyte, which produces wind-blown spores. These plants have an independent nonvascular gametophyte produce flagellated sperm swim in external water to reach the egg. i) Pteris: It is found in wild state in some regions of Punjab but in Sindh it is a common ornamental plant. The main plant is a sporophyte having adventitious roots, under ground stem-rhizome, pinnate compound leaves called fronds and sporangia in sori found under the surface of sporophyll (sporangia bearing leaves). ii) Adiantum: It grows in the wild. It resembles with pteris except the shape of leaflets, which are comparatively broad and arranged alternately. The main plant is sporophyte, a small herb which consists of a stem, roots and leaves.


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Stem — short, thick, rhizome. Roots— fibrous and adventitious, arise from the lower side of rhizome. Leaves— large and pinnately compound, having rachis bearing leaflets or pinnae arranged in an alternate manner. Lower pinnae are further divided into number of pinnules. Sori— on the under surface of the margin of fertile pinnules occur the sori. Each sorus consists of a number of small spore producing bodies sporangia. Spores after liberation from sporangium develop into small gametophyte called prothallus. 6.3 SPERMATOPHYTES — The seed producing plants: Spermatophytes (Sperma = Seed, Phyton = Plant)are seeds producing plants, which are divided into two major groups, gymnosperms and angiosperms. This division is based whether ovules are naked or covered. This gives rise to naked or covered seeds. The covering structure is called ovary, which develops into fruit in angiosperms. 6.3.1 Gymnosperms: (Gymnos = Nakecf; Sperma = Seed) Gymnosperms have naked ovules produced in cones. Ovules develop into naked seeds as fruit is absent due to the absence of ovaries. We will study Pinus as the representative of gymnosperms. Among the first seed-producing plants were the gymnosperms, which produce naked seeds. The four divisions of these plants are probably not closely related. PINUS: Pinus plant is very tall and thick. The height may be 40 to 50 meters and thickness may be up to 2 meters. It has well-developed root, stem, leaves and reproductive bodies called cones/ It has naked seeds as fruits around it does not develop. A conifer is the most typical example of a gymnosperm. In the conifer life cycle, windblown pollen grains replace swimming sperm. Following fertilization,! the seed develops from the ovule, a structure that has been protected within the body of the sporophyte plant. The seeds are uncovered and dispersed by the wind. Roots: It has well-developed tap roots. Lateral roots are longer than primary roots. Stem: The main stem has two types of branches called long-shoots and dwarf shoots. Leaves: The leaves are also two types of which are foliage and scale-leaves. Foliage leaves are popularly called needles because of their shape. They are green and found only at the apices of dwarf branches. They perform the function of photosynthesis. Scale leaves are sessile, thin and brownish. They are present on main stem as well as on both types of branches. Cones: Cones are unisexual and called male and female-cones.


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Male cones: They arise in cluster near the ends of long shoots. They are very small and never longer than 2cm;Each male cone has a central axis called thalamus or torus. This axis has 60 to 100 very small scales called microsporophylls. Each microsporophyll has sac like microsporangium which produce small spores called microspores. These microspores develop into winged pollen grains and are liberated in air. Female cones: They develop singly in place of dwarf-shoots. They are larger in size and measure upto 20cm in length and upto 10cm in width. Each female cone has an elongated axis (thalamus) on which large number of paired scales are present called megasporophyll having megasporangium or ovule, each ovule produce 4 comparatively large megaspores, out of these four, one will survive and develop into female gametophyte. Gametophytes of Pinus: Male gametophyte: Each microspore after pollination, is transferred to female cone and undergoes a period of rest in pollen-chamber, which is inside megasporangium. During next season, microspore germinates to form reduced male-gametophyte. It consists of prothallial cell, elongated pollen-tube having tube cell, stalk cell and two sperms or male gametes. Female gametophyte: Each functional megaspore develops into a body called female gametophyte within megasporangium. Each gametophyte has two archegonia each having single ovum. Fertilization and formation of seed: One of the male gamete fuses with the ovum to form oospore, becomes diploid. It develops into an embryo. In the mean time, the whole megasporangium develops into seed. Pinus seed has seed coat, endosperm and an embryo with an axis to which 6 to 10 cotyledons are attached. The two ends of the axis have plumule and radicle. Pinus seed has epigeal germination and gives rise to pinus plant. THUJA: In Thuja, the female cones are small, spherical or oval in shape and about the size of a spherical fruit locally called "bair" (berry). They consist of hard brown colour scales with triangular apices. 6.4 ANGIOSPERM More than half of the plants present on earth belong to this group. Angiospcrms are those flowering tracheophvtes which produce seeds within fruits. This is because the angiospermic flowers have ovules enclosed in the ovary. Angiospcrms are divided into two major groups monocotyledons and dicotyledons having one and two cotyledons (seed leaves), respectively. 6.4.1 Parts of Angiosperm: The body of an angiospermic plant may be divided into two parts, namely vegetative and reproductive parts. Vegetative parts have root, stem and leaves. Reproductive parts are flower, fruit and seed. These vegetative parts and reproductive parts of angiosperm have already been discussed in chapter 2 with reference to Brassica campestris. In angiosperms, the reproductive structures are located in the flower, which consists of highly modified leaves.


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6.5 MORPHOLOGICAL DIFFERENCES BETWEEN DICOT AND MONOCOT PLANTS Dicot plant *Plants produce two cotyledon (seed leaves) containing seed. *Roots are mostly branched tap root. *Stem is mostly branched. *Leaves are comparatively small with reticulate venation. 6.6

Monocot plant *Plants produce only one cotyledon (scutellum) containing seed. *Roots are mostly adventitious. *Stem is mostly unbranched. *Leaves are comparatively large with parallel venation.

Importance of Vascular plants:

Importance of vascular plants are: 1. Many vascular plants specially angiosperms are source of food e.g. wheat, rice, maize, pulses etc. 2. Many vegetables come from vascular plants e.g. potato, cauliflower, radish, carrots, bean, lady finger, tomato, onion etc. 3. Many ingredients of our food also come from vascular plants e.g. mustard, sugar, coconut, etc. 4. Many plants used as fodder belong to this group e.g. grasses, sorghum, burseem, jantar etc. 5. Many delicious fruits come from vascular plants e.g. Apple, mango, apricot, banana, citrus etc. 6. Timber is obtained from these plants, e.g. pinus, deodar, cedrus, sheesham, kikkar etc. 7. Many useful things are obtained from these plant, which serve as medicine e.g. Amaltas, cinchon, Ajwain etc. 8. Fibre of some plants are used in making cloth and rope such as cotton and jute. 9. Many plants are used for beautification as ornamental plant e.g. Rose, jasmine, shoe flower, glory of night etc.


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  

  

 


SUMMARY Plants may be defined as multicellular, eukaryotic, chlorophyllous living organisms having cell-wall made up of cellulose and their zygotes develop into an embryo. Bryophytes are the simplest group of plants. They are relatively poorly adapted to life on land, so are mainly confined to damp shady places. They are amphibious needing water for sexual reproduction. Bryophytes show distinct heteromorphic alternation of generation. It means the two generations called gamctophyte and sporophyte are morphologically as well as cytologically different. In contrast to other plants, bryophytes have dominant gametophyte (Haploid). Tracheophyte are the plants, which have conducting or vascular tissues. Nearly, all tracheophytes have well developed root, stem and leaves. Ferns are the common and important group of pteridophytes. They are found growing in moist cool, shady places. The common examples of ferns are Dryopteris, Pteris, Adiantum, Marsilea etc. Spermatophytes produce seeds. Spermatophytes are divided into two major groups called gymnosperms and angiosperms. Gyrnnosperms have naked ovules because cones are without ovaries. Ovules develop into naked seeds as fruits are absent due to the absence of ovaries. The body of an angiospermic plant may be divided into two parts, namely vegetative and reproductive parts. Each part is subdivided into different organs. Flower is a highly modified form of a branch, which is responsible for the reproduction of plants by producing seeds within fruits.


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1.

2.


EXERCISE Fill in the blanks with appropriate : i) Bryophytes are one of the two groups of plants, the other being________. ii) The dominant generation in bryophytes is _________ generation. iii) Sporophytic generation is partly or completely dependent on gametophyte in ______________ plants. iv) Adiantum has spore producing bodies found at ___________ . v) Gymnosperms have ________ ovules. Write whether the following statements are true or false: i) Funaria has true leaves. ii) Water is necessary for fertilization in Marchantia. iii) The other name of Pteris is Adiantum. iv) Dryopteris plant belongs to Musci of Bryophyta. v) Tracheophyta have trachea in the xylem.

3.

Encircle the appropriate answer: i) The group of Marchantia is (a) Hepaticae (b) Musci (c) Mosses (d) Anthoceratae ii) The group of Funaria is (a) Hepaticae (b) Musci (c) Anthocerotae (d) Hornwort iii) The group of Anthoceros is (a) Hepaticae (b) Musci (c) Liverworts (d) Anthocerotae iv) Typical flowers are present in the group of spermatophyte (a) Gymnosperm (b) Angiosperm (c) Pteropsida (d) All of them v) Horse tails are the common name of (a) Psilopsida (b) Lycopsida (c) Sphenopsida (d) Pteropsida

4.

Write detailed answers of the following questions: i) What are plants? Give general characters and groups of bryophytes and tracheophytes with examples. ii) Differentiate between gyrnnosperms and angiosperms. Describe any gymnosperm that you have studied. iii) What are the different parts of an angiospermic plant? Describe the parts of a flower in detail. iv) Describe the characters and groups of tracheophyta.

5.

Define the following : i) Bryophytes ii) Plants iii) Tracheophytes iv) Gyrnnosperms v) Angiosperms vi) Spermatophyte

6.

Differentiate between: i) Sprophyte and gametophyte. ii) Bryophyta and tracheophyta. iii) Antheridia.and archegonia. iv) Angiosperms and gymnosperms. v) Male and female cone. vi) Monocot and dicot plant.


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Chapter 7 INVERTEBRATA

Unicellular organisms are considered to be in the phylum Protozoa. Multicellular animals called metazoa are divided into two groups those that have backbones are called vertebrates; those that do not have backbones are called invertebrates. More than 95% of all of the animal kingdom are invertebrates. They have many diverse forms and ways of life. Learning objectives: * Invertebrates. * Diversity among invertebrates. * Important features of major groups of invertebrates. * Identification of invertebrates around you and their placement in proper groups. The Kingdom Animalia is broadly divided into two major groups: i) ii) 7.1

Invertebrata: Animals without back bone, Chordata/Vertebrata: Animals having ing, rod like structure) in their body.

a

back

bone (a

INVERTEBRATES

Animals, which do not have back bone in the bodies, are termed as invertebrates. They are greater in number, but usually smaller in size than vertebrates. Invertebrates are divided into many groups or phyla. Some of the important phyla are described below: 1. Phylum Protozoa: Phylum protozoa consists of unicellular (single celled), microscopic animals like organisms, which are now not treated as true animals. They occur either as freeliving (e.g. Amoeba, Paramecium, Euglena, etc.) or as parasites, which depend upon other living organisms for their nourishment and shelter. Common protozoan parasites are Plasmodium and Entamoeba histolytica which cause, important human diseases malaria and dysentery, respectively. Free-living protozoa are chiefly found in water, both in fresh as well as in marine water. Paramecium lives in fresh water pond. Its surface is covered by thousands of very fine, hair-like structures called cilia which help in locomotion. Paramecium has two nuclei, one is larger called macronucleus while the other one is smaller called micronucleus. Outside the cell membrane, a flexible, non-living covering or pellicle provides it a definite shape. According to the recent classification protozoa is not included in kingdom animalia but has been placed in kingdom Protoctista (Protista). 2. Phylum Porifera: Porifera are the simplest group of multi-cellular (many celled) animals. Their bodies consist of loose aggregates of cells and lack any kind of tissues. The entire body has numerous minute pores or ostia. Porifera are commonly termed as sponges. All sponges are aquatic (live in water) and sessile (fixed at one place throughout their life). The surrounding water enters into the body through ostia, which leads through channels into a hollow space inside the body, where the inner cells of sponges filter out the microscopic food particles. The water then leaves the body of sponge through another opening, the osculum.


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Sponges have an internal skeleton of hard structures called spicules, which are formed of calcium carbonate or silica. The spicules provide and shape to the multi-cellular body of a sponge. Common examples of sponge are Sycon, Venus flower basket and bath sponge. Sycon has a flask-like shape and contains needle-like spicules of calcium carbonate. It is a colonial form which is found in shallow water in being attached by a sticky secretion to some submerged solid object like rocks, shells of molluscs and corals. It is one to three inches in length-and grey or light brown in colour. The free end of each opening, the osculum. 3. Phylum Cnidaria (Coelenterata): Coelenterates are aquatic animals. Most of them are marine but some are found in fresh water. Cells of coelenterates are organized to form tissues. They are called diploblastic because their cells are arranged in two layers; an outer ectoderm and an inner endoderm. In between these two layers are a jelly like, non-living layer called mesoglea. Many of the coelenterates arc sessile (remain fixed) (e.g. corals) while others are motile e;g Jelly-fish. They occur as free living animals, cither living singly e.g. Hydra or in the form of a colony e.g. Obelia. Hydra is a fresh water coelenterate which can be better seen with a microscope. Its body is cylindrical with several thread-like tentacles at its one end encircling an opening called mouth. Both, the tentacles and the ectoderm bear a number of poisonous, stinging cells for defence and for paralyzing the prey. The tentacles are used for capturing the prey. The mouth opens into a hollow space or coelenteron that lies inside the body. The prey is digested in the coelenteron. The end of body of hydra opposite to the mouth is normally kept attached to some object in water. Jelly fishes live in the sea. They have an umbrella like body with thicker body walls. They swim freely in water. The mouth is located in the center of the downside of umbrella. It is encircled by four long arms each bearing numerous stinging cells. The long arms are used for capturing small animals. 4. Phylum Platyhelminthes: Platyhclminthes arc commonly called flat-worms because of their flat body. They occur mostly as parasites of animals as well as man. Howover, some are freeliving such as Planaria which- lives in fresh, water streams. Platyhelminthes are triploblastic animals because of the development of a middle layer of cells, the mesoderm, in between ectoderm and endoderm. Liver fluke is a flat leaf shaped organism about 3 cm in length. It is a parasite in the liver of sheep, goat and cattle. It attaches itself with its host with the help of two suckers, one around mouth at the anterior tip while the other slightly behind the first on the ventral side of the body. It has a bifurcated, highly branched digestive system. The anus is absent in them. Each liver fluke has both male and female reproductive organs. It causes considerable damage to the infected cattle. Tape worms live in the intestine of their vertebrate hosts. Their bodies are long, ribbon-like and divided into series of segments. The anterior end is some what rounded and head like. It is provided with four suckers and rings of minute hooks which help them to attach with their host. Tape worm lacks digestive system, mouth and anus. It absorbs the digested food of its host through its body surface. Every segment has a set of male and a female reproductive organs.


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5. Phylum Nematoda: Nematodes or round worms have long, smooth, cylindrical body, which is pointed at both the ends. The body is unsegmented. Nematodes have a complete and one way digestive tube with mouth at the anterior tip while anus near the posterior tip. They are free-living as well as parasites of animals, man and even plants. The most common round worm infecting man is Ascaris lumbricoides commonly called human round worm. It lives in the intestine of man. Sexes are separate in round worm and male is slightly smaller in length than female. 6. Phylum Annelida: Animals in this group have elongated, segmented body. The segmentation in annelids is both external as well as internal. Internally, many organs are repeated in every segment of the body. Annelids occur in water as well as on land. Most of them are free living e.g. earth-worm, etc. while few are ectoparasites e.g. leech, etc. They have well developed organ-systems in their bodies. However, respiration occurs through their general body surface. An important feature of annelids is their advanced closed type circulatory system i.e blood circulates in blood vessels being pumped by. a number of simple hearts. The leech lives in ponds. It attaches with the help of its suckers to man and other animals that come in with water. It sucks the blood of its host. 7. Phylum Arthropoda: Phylum Arthropoda is the largest phylum of Kingdom Animalia. They have ted limbs (legs). Their body is covered externally with a hard covering called exo-skeleton which is made up of a complex chemical called chitin. Arthropods occur on land as well as in water. The body of an arthropod is usually divisible into three distinct regions; an anterior head, a middle thorax and a posterior abdomen. Scorpions, spiders, crabs, prawns, centipedes and insects are the common arthropods. Insects are the most abundant animals on earth. They all have three pairs of legs, two pairs of wings and one pair of sensory hair-like antenna. Many of them have wings to fly. Insects have special types of mouth parts (appendages for food handling) according to their mode of feeding, for example mouth parts of mosquito, housefly, butter fly and cockroach have different types of mouth parts. Many insects such as mosquitoes hatch out of their eggs in a premature form and through different stages of development to reach the adult stage. This phenomenon is called metamorphosis. Metamorphosis is of two types: i) Complete metamorphosis ii) Incomplete metamorphosis i) Complete metamorphosis: In complete metamorphosis, the young one, the larva, which hatches out of egg is morphologically completely different from adult. It feeds actively and then encloses itself in a cover to become pupa. After going through farther changes, the pupa comes out of its capsule, it is now termed adult. Thus, (The life cycles complete after ing through these insect es through egg, larva, pupa and adult stages. Insects such as butter flies, mosquitoes, house flies, etc. undergo complete metamorphosis. ii)

Incomplete metamorphosis:


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In this type, the young one, called nympn which emerges out of egg is a miniature young one which closely resembles the adult except that it lacks wings and its reproductive organs are immature. After the development of wings and maturity of reproductive organs, the nymph becomes adult. Incomplete metamorphosis is observed in insects like grass-hopper, cockroach, termite, etc. Common insects are house-fly, butter-fly, mosquito, cockroach, honey-bee, termite, etc. 8. Phylum Mollusca: Animals of this group have a soft, fleshy body enclosed in a thin fleshy cover called mantle. Many molluscs are covered over externally by a hard, non-living shell made up of calcium carbonate. They mostly occur in water but some are found on land. A fleshy organ or foot is given out of the shell on the ventral side of the body. It helps in locomotion. The structure of shell plays an important role in identification and further grouping of molluscs. Common examples of molluscs are snail, pearl oyster, squid, octopus, and fresh water mussel. Squids are the largest invertebrates. Snails have spirally coiled shells and are commonly seen in lawns and gardens. Fresh water mussels are aquatic and have a shell composed of two plates ed together by a hinge t. 9. Phylum Echinodermata: Echinodermates have rough, spiny skin. They are found only in the sea. They are pentamerous and have a unique water vascular system which pumps the external water throughout their bodies. This vascular system operates the soft, tube shaped feet (tube feet) which enable the animal to glide over the rocks in water. They do not have head, eyes or even brain. Common examples of phylum echinodermata are star-fish-, sand-dollar, sea-cucumber, sea urchins etc. Star-fish has a plate-like central disc with five or more arms extended out from it. Sea Urchin has a ball-like body without arms. Its body is covered over externally by long spines.


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SUMMARY           

Invertebrates do not have back bones in their bodies. Invertebrates are divided into a number of smaller groups or phyla. Major phyla of invertebrates are Protozoa, Porifera, Coelentcrata, Platyhelminthes, Nematoda, Annelida, Arthropoda, Mollusca and Echinodermata. Protozoa are unicellular animal like organisms which are now placed in kingdom Protoctista (Protista). Porifera or sponges are multicellular but without tissues. Coclentcrates are multicellular and diploblastic. Platyhelminthes are flat and triploblastic. Nematodes have elongated, un-segmented body pointed at both the ends. Annelids are commonly known as segmented worms. Arthropoda is the largest phylum. They have ted legs. Around 95% of the arthropods are insects. Insects have 3 pairs of ted legs. Molluscs have soft fleshy body enclosed in a soft membranous cover called mantle which may be covered over by a hard shell.


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EXERCISE 1.

Fill in the blanks with appropriate : i) ii) iii) iv) v) vi) vii)

2.

Write whether the following statements are true or false: i) ii) iii) iv)

3.

ii) iii) iv)

It is not multicellular. (a) Porifera (b) Arthropoda (c) Nematoda (d) Protozoa. These are exclusively marine. (a) Protozoa (b) Annelida (c) Echinodermata (d) Mollusca. Spiders do not have (a) ted legs (b) Wings (c) Exoskeleton (d)Head Which of the following is free-living? (a) Plasmodium (b) Tapeworm (c) Hydra (d) Liver fluke.

Write detailed answers to the following questions: i) ii) iv) iv)

5.

Dysentery is caused by Plasmodium. Nematodes are segmented worms. Spider, prawn, scorpion belong to phylum Annelida. Water vascular system is a feature of sponges.


4.

The external, protective covering which develops in arthropods is called __________. Malaria is caused by _________. Animals fixed at one place are called ________. _________ is a parasite in the liver of sheep. House flics, mosquitoes, butterflies belong to class ________. Molluscs move by means of a fleshy organ called _________. Echinodermates have ________ skin.

State and explain important characters of round worms and segmented worms. Discuss important characters of Phylum Arthropoda. Give general characters of echinodermates. Discuss important features of diploblastic animals. .

Write short answers to the following questions: i) ii) iii) iv) v) vi)

Sponges are sessile. How do they get food while staying at one place? You have studied different groups of animals. Make a list of few tripoblastic invertebrates beginning from the simplest forms. What do you know about insects? What is exoskeleton? Name two phyla of animals having exoskeleton. Define parasite. Name five parasites and the phyla to which they belong. Write short notes on Hydra and tape worm.


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Chapter 8 CHORDATA / VERTEBRATA This unit introduces the most advanced of all the animals—the vertebrates. All vertebrates have a spinal column made up of bones called vertebrae. Inside the spinal column is the nerve cord. This cord is ed to highly developed brain. This system makes its possible for the vertebrate to respond to stimuli in a very effective way for its own survival. This superior nervous system is the real key to the biological supremacy of vertebrates. Learning objectives: * The chordates. * Vertebrates relation with chordates. * Major groups of vertebrates. * Important features of vertebrate groups. Animals such as cat, dog, bird, frog, fish, etc. which you commonly observe around you belong to the phylum Chordata. Human beings also belong to this group. Although, chordates are less numerous in number than invertebrates, yet they occur in greater diversity. The name chordata given to this group is due to the presence of a solid, elastic, rod-like ing structure, the notochord. It is one of the basic features present in all chordates. In addition to the notochord, all chordates have a dorsal, hollow, tube-like nerve cord and many pharyngeal gill slits which appear as paired openings in the walls of pharynx. Notochord, hollow dorsal nerve cord and pharyngeal gill slits are considered as the basic features of all chordates. These basic features are essentially present in all the chordates during their embryonic period. Later in adult life, they may be modified or even lost. . 8.1 VERTEBRATA Most of the chordates belong to the group vertebrata. It is the group of chordates in which notochord is replaced by a series of bones, called vertebrae, arranged in the form of a column being termed as vertebral column. Their brain is also protected in a brain box. Vertebrates are usually categorized into following classes. 1) Pisces (Fishes) 2) Amphibia 3) Reptilia 4) Aves (Birds) 5) Mammalia 1. Class Pisces (Fishes): The pisces (Fishes) am entirely aquatic vertebrate animals. The body of fish is stream-lined (spindle shaped) to offer less resistance to water while swimming. They breathe by means of gills. Their body can be differentiated into head, trunk and tail. The skin is usually covered with scales. They bear paired fins rather than legs which help them in swimming. Mouth has teeth which are used for cutting, tearing or grasping the food. They are not used for grinding the food. Fishes are cold blooded animals, i.e. their body temperature is variable (changeable).Common examples of this group are sharks, Labeo (RohuArout, Hilsa (Pullah), and Catfish (Khagga). Labeo (Rohu) is a common edible fish found in fresh water. Its gills are covered with bony plates or opercula (Sing, operculum) and the skin has external skeleton of large scales.


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Fishes, the largest group of vertebrates, are very important source of food for animals as well as for man. Millions of people around the world are engaged in fishing industry. Fishing is also a popular sport throughout the world. 2. Class Amphibia: They live in water during their early life. Later, in adult life, they live in water as well as on land. For this reason they are termed as Amphibia (means dual life). These are the vertebrates with four limbs (legs) whose fingers are clawless. Breathing in early stages occurs through gills. In adult stage, gills are replaced by lungs. Adult amphibia have a naked skin which is thin, moist and slimy skin, which is also used for exchange of gases (oxygen and carbon dioxide). Like fish, they are cold blooded animals. Common examples of amphibia are frogs, toads, and salamanders.

= = = =

Facts about Frog: Common frog of Pakistan is Ranatigrina. Some frogs live on trees. Smallest frog found in Brazil. Largest frog found in Africa is about 30 cms in length.

Frog has a smooth, slimy, brightly coloured wet skin. It lives close to water. It jumps quickly in water in case of any danger on land. Toads usually have dull coloured skin with less jumping capability. The eggs of frog are laid in water. The immature young one which hatches out of egg is called tadpole larva. It undergoes metamorphosis (series of changes) to become a small frog. During winter, in order to avoid low temperature, frogs burry themselves in the mud present at the bottom of pond. This phenomenon is called hibernation. 3. Class Reptilia: Reptiles are considered as the first, completely terrestrial (land) vertebrates. Unlike amphibia, they lay their large shelled eggs on land rather than in water. Their dry skin is covered with epidermal scales. They breathe by lungs. Majority of reptiles live on land. However, some are also aquatic. The limbs have digits with claws. Both the jaws in reptiles bear teeth. Most of them are cold blooded. Very early reptiles called dinosaurs were huge animals but they do not live now. Among the living reptiles lizard, tortoise, turtle, snake, crocodile are common examples. House (Wall) lizard is familiar to you. It feeds on insects. It crawls on walls or even on ceilings because of special kind of adhesive pads on their fingers. Snakes are the limb-less reptiles. Some of them (e.g. Cobra) are well known for their deadly poison. Poison called venom is produced in the poison glands located near the upper jaws. Poison is injected into the prey through special, long pointed teeth called fangs which can regenerate if broken. The rest of the teeth have nothing to do with injecting poison. In fact, most snakes are non-poisonous. 4. Class Aves (Birds): This class includes all the birds. The birds are the vertebrates whose bodies are covered externally with feathers, fore-limbs are modified to form wings, mouth is tooth-less and jaws are prolonged into beak and their bones are hollow and light. Most of the birds can fly with the help of their wings and feathers. They can walk or even swim with the help of their hind limbs (legs). Although birds live on land, some birds are also aquatic and can live in water. The melodious voices of many birds you hear come from a special sound box, syrinx present at the base


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of their neck. Their eggs are large, covered by a hard shell and contain great amount of reserve food usually in the form of yolk. Eggs are laid on land. The birds maintain a constant body temperature so they are termed as warm blooded animals. Parrot, sparrow, pigeon, ostrich, kiwi are some of the common examples of birds. Humming bird, the smallest bird of the world is about 2 inches in length. it feeds on the nectar of flower. Ostrich is the largest bird of the world. Its egg is about 1 to 2 lbs in weight Pigeons were used to serve as a means of dispatching letters in the old times. Pigeon rearing and flying was once a very common sport. Pigeons are among the modern birds which can fly for hours in the skies. Kiwi, found in New Zealand is a good example of birds which have lost the power of flight. Their wings are short and feathers are hair-like. Therefore, such birds are termed as flight-less birds. 5. Class Mammalia: Mammals are named so because of the presence of mammary glands in their skin. Mammary glands are functional and secrete milk in females, which is used to feed their young ones. The skin of mammals is covered over with hair. In addition to mammary glands, skin also contains sweat glands, sebaceous glands and scent glands. Both upper and lower jaws in mouth bear various types of teeth. Like birds, they are also warm blooded animals. Most of the mammals give birth to live young ones. Mammals can be divided into three subgroups. a) Egg laying mammals,

b) Pouched mammals, c) Placental mammals

a) Egg laying mammals: These are relatively simple among mammals. Like reptiles, they lay eggs. However, like mammals, they have mammary glands so they feed milk to their young ones. Since they have characters of both reptiles and mammals, they are considered to be connecting link between reptiles and mammals. Duck billed platypus and the spiny ant eater are the only living examples of this group. Both are found only in Australia. b) Pouched mammals: They give birth to premature babies. As the new born babies are weak, the mother keeps them in a pouch on its belly until they develop fully and become strong enough for independent life. Inside the pouch, opening of mammary glands are present for feeding milk to the young one. Kangaroo, koala bear and opossum are common examples of pouched mammals. c)

Placental Mammals:

Most of the mammals including man belong to this group. In placental mammals, the young one completes its development inside the body of its mother where it is fed through on organ called placenta. After birth, the young one is fed on mother's milk secreted from the mammary glands. Common examples of placental mammals are man monkey, elephant, rat, cat, lion, bat, seal, whale and dolphin.


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Although mammals are chiefly terrestrial, some (e.g. whale dolphin seal, etc) live in water. Blue whales are the largest living animals in the world. Bats are unique as they can fly. 8.2 LOCAL FLORA AND FAUNA OF PAKISTAN Pakistan has a long stretch of high mountains in its north and north-west, plateaus in Baluchistan and Potohar, plains of Indus and patches of deserts in Punjab and Sindh. This environmental and climatic variety s an immense diversity of both plants and animals. Thus when we speak of flora, we mean plant life and when we speak of fauna, we mean animal life. Our interest in flora and fauna of Pakistan is not only due to our desire to know our plants and animals but also because our economy and environment depend on them. It is our duty to take care of these valuable gifts of nature. 1. Flora: Our country has representatives of all groups of plants which you have studied. Although all of them are important in their own way, forests are especially noteworthy. Forests and forestry are considered to be the backbone of our economy. They regulate the qualities of water in the rivers by preventing the free flow of soil in water by holding it with their roots. They prevent formation of deserts, control water logging and maintain the amount of salts in the soil and regulate the temperature of atmosphere. They not only supply oxygen to the air but also provide food and shelter to animals (wild-life). They are an integral part of our ecosystem. Can you guess what may happen to our wild-life if forests are cut down? Some of the economically important flowering and non-flowering plants of Pakistan are discussed below: The high mountains in the northern and north western part of Pakistan, due to sufficient snow fall, thick forests. These forests consist of trees like blue pine, chir pine, chalghoza pine, deodar, fir, juniper and olives, etc. Forests of desert plants like Acacia are found in the areas where there is less rain fall and scarcity of water. Trees of Sheesham, Mulberry, Willow, Poplar, Neem etc. are found in irrigated lands like Changa Manga. These forests play a key role in providing us wood for furniture, sports goods and fuel. In the plains many crops are cultivated which fulfill our nutritional and other requirements. These crops include wheat, maize, rice, sugar cane, sugar beet, pea, potato, tomato, onion, garlic, chili, turnip, radish carrot, cauliflower, many cereals, grains and cotton, etc. Pakistan is also rich in fruit bearing trees like mangoes, apples, apricots, peaches, oranges, bananas, walnut and almonds etc. Many plants are cultivated for ornamental purpose e.g. Chrysanthemum, roses and jasmines etc. The hills and plains of our country possess various types of grasses, which provide fodder for our grazing animals. Still a large number of plants like Typha, Hydrilla, and many types of algae are found in fresh water ponds, lakes, streams and river. A variety of marine plants are found in oceans and coastal regions of our country. The above mentioned plants not only provide us food but are also important for their medicinal values. Some plants form thick forests from which we get timber while some plants are cultivated for ornamental purposes. Is it not a good idea to prepare a list of plants found in your locality? It will increase your knowledge of the flora of Pakistan.


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2. Fauna: Like flora, our fauna is also full of variety of animal groups learned by you. Each one of these groups holds an important position in its biological relationship with plants and with human beings. You have learnt a bit about these relationships in your previous classes. There are, however, a few facts which you should . The coastal and offshore waters of Sindh and Baluchistan are rich in seafood. These are considered to be one of the best fishing grounds in the world.. Can you list the types of animals which make up sea-food? Obviously, fishes would appear in this list as a major group of economic value. Fishes in large number and variety are found in our sea. This is in addition to the fishes in our rivers and lakes. Fishes in general are of great commercial value. Common fishes of Pakistan include rohu, pullah, khagga, trout, maha8heer, flat fish, sea horse, malee, skates, rays, scoliodon (dog-fish), etc. You are undoubtedly familiar with our common amphibians, frogs and toads. Our reptiles include crocodile, lizard and turtles. Cobra, krait, vipers and pythons are among our common snakes. Our country is rich in a variety of flying birds, though we do not have any representation of the flightless birds group. Every year large number of migratory water birds like ducks visit our lakes. These together with quails, partridges and the beautiful pheasants constitute a group called game birds. Other common birds are Houbara bustard, crane, water fowl, falcon, eagle, kite, peacock, pigeon, crow, parrots etc. Mammals make up a major part of our wild and domesticated animals,You already know much about our cattle. We have a variety of deer. These together with ibex (a wild goat) and urial (a wild sheep) attract hunters. Uncontrolled hunting has endangered their survival. Although we have many mammals of the carnivore group, we have lost the tiger and the lion perhaps due to hunting. Our monkey is endangered because of its great demand in overseas markets. Don't we need to do something about it? The most important group of mammals being associated and helpful to man is ungulates, the hoofed mammals. They provide us milk and meat. Many have been domesticated for fun and as beast of burden. Pakistan has large variety of these animals. Common representative are wild goats, sheep, deer, gazelles, markhores etc. Cows, buffaloes, donkeys, horses! goats and camels are the common domesticated forms. Grey Langur, Rhesus monkey, Markhor, Snow Leopard, Wolf, etc. are much endangered animals of Pakistan. This brief of our fauna gives you some idea about our animal life. Fauna and flora are biologically inseparable because of their interrelationship and have an impact on our own welfare or even survival. Fauna, flora and man form a kind of a triangle in which there is a natural balance. If this balance is disturbed, each one would be negatively affected. One component of this triangle which can help make or break this balance is the human being himself.


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          


SUMMARY Chordates have a notochord in their bodies., in vertebrates notochord is replaced by vertebral column. The group vertebrata includes most of the chordates Vertebrates are divided into pisces, amphibia, reptilia, aves and mammalia. Pisces, amphibia and reptiliaare cold blooded animals. Aves and mammalia maintain their body temperature and are called warm-blooded animals. Pisces have paired as well as unpaired fins on their bodies. Amphibia have four limbs with clawless digit. Snakes are limb-less reptiles. Birds have wings and feathers. Most mammals give birth to young ones. Pakistan enjoys a variety of geographical and climatic conditions which a great diversity of fauna and flora.


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1.


EXERCISE Fill in the blanks with appropriate : i) The name chordata refers to the presence of a solid, elastic rod like, ing structure called the___________ . ii) Most of the chordates belong to the group____________. iii) The skin of fish is usually covered over with ________. iv) Amphibia means____________. v) Birds and mammals are _________ blooded animals.

2.

Write whether the following statements are true or false: i) Adult frogs are gill breathers. ii) Snakes can inject poison into their prey through all their teeth. iii) Birds have hair on their skin.

3.

Encircle the appropriate answer: i) It is not cold blooded. (a) Fish (b)Cat (c)Frog (d) Snake ii) Which of the following is gill breather? (a) Frog (b)Fish (c) Whale (d) Turtle iii) It lives no more in the world. (a) Kiwi (b)Deer (c) Tiger (d) Dinosaur iv) It gives birth to young one. (a) Pigeon (b) Turtle (c)Dog (d)Toad v) It has no teeth in mouth. (a) Shark (b)Frog (c) Elephant (d) Sparrow

4.

Write detailed answers of the following questions: i) Write down the important characters of each group of warm blooded animals. Give examples. ii) Discuss the important flora and fauna of Pakistan. iii) What is Pisces? Discuss their important characters. iv) Explain general characters of reptiles. v) Discuss general characters of the vertebrates with naked skin.

5.

Write short answers of the following questions: (i) Make a list of basic characters of chordates. (ii) Why are amphibia regarded as having "dual life"? (iii) Define the , "cold blooded" and "warm-blooded"? (iv) What is a vertebrate? (v) Define the operculum, hibernation, fangs, fauna and flora.


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SECTION 4 MAINTENANCE OF LIFE Life is the sum-total of a vast number of activities going on inside the body. It is like a factory, a place of great activity, where fuel and raw materials are taken and converted into finished products and energy. These finished products form the new cells. Energy keeps this machine system working and up till these major systems are working, in co-ordination, organism is alive whenever they stop, life ceases to survive.

Chapter 9 FOOD AND NUTRITION To remain alive and to maintain the body processes all organisms take in nutrients. Nutrients are chemical substances needed by the body. They provide energy, the fuel of life. They repair the older body cells and form new ones. Learning objectives:          

Introduction of nutrition and nutrients. Importance of food to obtain nutrients. Synthesis of macro molecules from micro molecules. Autotrophic nutrition in plants. Mineral requirements in plants for photosynthesis. Special modes of nutrition in plants. Heterotrophic nutrition in animals. Nutrition in human beings and components of their food. Concept of balanced diet and its importance. Disorders of the gut.

All living organisms require energy to carry on their life processes. To meet these demands they intake two main categories of molecules from environment: already synthesized high-energy compounds (food) or the raw materials from which new protoplasm can be synthesized. The intake and processing of these materials is called nutrition. Materials required for the synthesis of new protoplasm as well as for the production of energy are called nutrients. 9.1 NEED FOR FOOD All living organisms need food. They need it as a source of raw material to build new cells and tissues as they grow. They also need food as a source of energy. Food is a kind of fuel of living organisms like automobiles require petrol or diesel. In living organisms food drives essential living processes and brings about chemical changes. It provides essential materials to make proteins and enzymes. It also provides materials to maintain various processes of life such as reproduction, respiration etc. Living organisms can be divided into two groups on the basis of their mode of nutrition. (i) Autotrophic organisms (ii) Heterotrophic organisms (i) Autotrophic organisms: Organisms, which can synthesize their own organic compounds (food) from inorganic raw material taken from inorganic surroundings. The molecules of raw material are small enough and soluble to through the cell-membrane. Most of the autotrophs are photo synthetic e.g plants, algae some bacteria etc.


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(ii) Heterotrophic organisms: Organisms, which are unable to synthesize their own organic compounds (food) from simple inorganic nutrients. They obtain synthesized food from their environment. Many of the organic molecules found in nature arc too large to be absorbed unaltered through cell membranes and they must first be digested i.e broken down into smaller, more easily absorbable molecular units. The food of heterotrophic organisms consists of following components. 1. Carbohydrates 2. Proteins 3. Fats 4. Vitamins 5. Minerals 6. Water 9.2 SYNTHESIS OF LARGE MOLECULES FROM SMALLER BASIC UNITS Organic molecules in the living bodies are found in the form of either small or large, complex molecules. Most of them are large and complex. There are two ways to manufacture a large complex molecule: One could synthesize the molecule atom by atom or one could take pre-assembled smaller molecules and hook them together. Small molecules (e.g. Glucose) arc used as sub-units to synthesize longer molecules e.g. starch. The individual sub-units are often called monomers (Greek words meaning one part), long chains of monomers arc called polymers (many part). All polymers are synthesized by a process called condensation. In this process two monomers are ed together by the removal of a water molecule, as a result a bond is formed between two sub-units, this process is called dehydration synthesis.

  

Monomers Monosaccharides e.g. glucose Amino acids Fatty acid and Glycerol

  

Polymer Polysaccharide e.g. starch and glycogen Proteins Fats and oils

Simple Sugar to Starch and Glycogen: Starch, glycogen and simple sugar (glucose, fructose etc), belong to a group of organic compounds called carbohydrates. Carbohydrates contain carbon, hydrogen and oxygen. The most common simple sugar is grape sugar called glucose (C6 H12 O6). It is the most ready source of energy in cells. Fig: 9.1 Diagram showing how complex carbohydrates arise from simple sugar When molecules of simple sugar combine, they from complicated carbohydrate e.g. molecules of glucose and fructose combine to form a complex disaccharide sugar called sucrose (table sugar), found in sugar cane and beet root. When many simple sugar molecules in long chain, they form the most complex polysaccharide carbohydrates such as cellulose, glycogen and starch. Plant cells store extra carbohydrate as starch while animal cells store extra carbohydrate as glycogen which is some times called animal-starch. 9.2.2 Amino acid to proteins: Amino acids are the monomers that condense to form proteins, which are very large molecules. We can say that the building blocks of proteins are amino acids. There are 20 kinds of amino acids which combine in different kinds of proteins. Fig: 9.2 Formation of a simple Protein molecule by the combination of amino acids As you know that the English language has 26 letters of the alphabet and they form millions of different words. In the same way, the 20 amino acids form a


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great variety of proteins. The number of amino acids combined in most proteins molecules ranges between 300 to 3000. Main role of protein is to provide building material in the body. They help in growth and repair of body parts (healing). They make structures like muscles, nails and hairs. 9.2.3 Fatty acids and Glycerol to Fats and Oils: Fatty acids and glycerol are the monomers that condense to form fat or oil, which are insoluble in water due to absence of any polar group. A fat or oil is a molecule which is formed by the condensation of 3 molecules of fatty acid with a glycerol by removing 3 molecules of water. Oils are liquid at room temperature while fats are solid. Examples of oils are cotton seed oil corn oil coconut oil, soyabean oil. Fats generally come from animal source like butter, cream, etc. Organisms use fat molecules as long term energy storage compounds. Fig: 9.3 Diagram showing how fats are formed from glycerol and fatty acids 9.3 NUTRITION IN PLANTS From the view point of nutrition, the most important difference between animals and plants is that animals take in prepared organic food, digest it and use the digested products to build their tissues or to produce energy. Plants, on the other hand, first make the food they need and then use it for energy and growth. Majority of the plants are autotrophic in their mode of nutrition. Some are heterotrophic and live as parasites or saprophytes. Parasites obtain their food from other living organisms while saprophytes depend on dead organic matter. In dealing with life processes in plants in this chapter, we shall first discuss photosynthesis and its processes. 9.3.1 Autotrophic nutrition in plants: Photosynthesis: The process by which plants make their food is called photosynthesis. In this process a plant can build sugar by taking carbon dioxide from air and water from the soil. For the synthesis of sugar like glucose, carbon dioxide provides carbon and oxygen whereas water molecules provide hydrogen. The plant builds sugar molecules from these simple compounds. Enzymes needed for this purpose are present in the cells and energy is trapped by chlorophyll from sunlight. The process if completed in the mesophyll cells of the leaves as shown in Fig: 9.4. The reaction is expressed by the following chemical equations: 6CO2

+

Light Energy

6H2O

Carbon dioxide

Chlorophyll +

Water

(Raw material)

C6H12O6

+

Glucose

6O2

+ Oxygen

(Product)

This equation shows only the starting materials and end products of the process but gives no information about the intermediate reaction steps involved. It is also obvious that oxygen is produced as a by-product of photosynthesis. During day light, green plants take in carbon dioxide and give out oxygen. Thus, oxygen would appear here to be a waste product.


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Fig: 9.4 Photosynthesis in plants 9.3.2 Morphology and Anatomy of leaf related with Photosynthesis: In plants, leaves are the most appropriate structures which are adapted fog photosynthesis. There are wide variations in leaf shape and structure. The following characters explain their adaptability towards photosynthesis. 1. Their broad flat shape offers a large surface area for absorption of sunlight and carbon dioxide. 2. Most leaves are thin and the CO2 has to diffuse across only short distances to reach the inner cells. 3. The large spaces between cells inside the leaf provide an easy age through which C02 can diffuse. 4. There are many stomata (pores) mostly in the lower surface of the leaf which allow the exchange of CO2 and O2 with the air outside. 5. There are more chloroplasts in the upper cells than in the lower cell because the cells of upper surface receive more sunlight. 6. The branching network of veins and veinlets provide a good water supply to the photosynthesizing cells and no cell is very far from a water conducting vessel. Fig: 9.5 (a) The external appearance of leaf shows the transport tissues. Fig: 9.5 (b) Transverse section through part of a leaf. The leaves of most land plants are only a few cells thick. The upper and lower surfaces of a leaf consist of a layer of transparent cells, the epidermis. The outer surface of both epidermal layers are covered by a waxy, water proof covering, the cuticle that reduces the evaporation of water from the leaf A leaf obtains CO2 for photosynthesis from the air through adjustable pores in the epidermis called stomata which open and close at appropriate times to it CO2. Inside the leaf, there are a few layers of cells collectively called mesophyll (which means simply middle of leaf) where photosynthesis occurs predominantly. 9.3.3 Factors necessary for photosynthesis: Many factors, both external and internal are necessary for food synthesis in plants. The external factors are sunlight, water, carbon dioxide and temperature. The internal factor is chlorophyll. It is present in special structure within a cell called chloroplast. The following conditions are necessary for the process of photosynthesis in plants. 1. Light: Carbon dioxide and water are the basic constituents required for formation of glucose. However, they will not combine in the absence of sunlight because various reaction steps necessary for synthesis of glucose require energy input. This energy is supplied by light. As light is composed of seven colours; rays of two colours chiefly red and blue, are used in the process. Photosynthesis is also affected by the intensity of light. Very intense light is harmful, while light of moderate intensity accelerates and weak light slows down the rate of photosynthesis. In the total absence of light even the chlorophyll does not develop. Photosynthesis can also take place in artificial light. 2. Chlorophyll: Chlorophyll imparts green colour to the leaves. It traps the energy of sunlight and makes it available for use by the plant. Photosynthesis will not proceed without chlorophyll and that is why it occurs only in the parts of the leaf or stem that contain chlorophyll.


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3. Carbon dioxide: Plants get the carbon dioxide to be used during photosynthesis from the air. It enters the leaf through the stomata. It is used as a source of carbon for glucose. Photosynthesis will not take place without carbon dioxide. Although it comprises only 0.03 to 0.04% of the air, its supply does not exhaust as it is continuously recycled into the air. The process of photosynthesis accelerates if its proportion is increased up to 1.0%. However, greater amounts of carbon dioxide, adversely affect the process. 4. Water: This constituent is as basic as is carbon dioxide. Water is important in photosynthesis in two ways; firstly, it provides hydrogen for the building up of glucose and secondly, opening and closing of stomata is regulated by increase or decrease in the amount of water. It is important that stomata should remain open so that carbon dioxide may enter leaves. Water together with salt (e.g. nitrates), absorbed by the roots ultimately reaches leaves where it is used in photosynthesis. 5. Temperature: Suitable temperature is also necessary for photosynthesis. Normally a temperature range of 15°C to 30°C is most suitable for this process. At higher temperature the rate of photosynthesis starts declining and at 45°C it completely stops. However, depending on regions, the temperature requirements of the plants may change. For example, this process occurs at a temperature range from 0°C to 10°C in plants of cold and mountainous regions. 9.3.4 Conversion of light energy into chemical energy: Photosynthesis is the metabolic process by which plants trap light energy, convert it into chemical energy and store it in the bonds of organic nutrient molecules such as glucose and release O2 as by-product. Light Energy 6CO2

+

6H20

Chlorophyll

C6H12O6 + (Glucose)

6O2

The simple looking chemical reaction of photosynthesis actually involves dozens of reactions. These reactions occur at different sites in the chloroplast. Whole photosynthesis process is mainly divided in two stages. 1. Light reaction 2. Dark reaction 1. Light reaction: Light reaction is also called light-dependent reaction because chlorophyll and other molecules capture light energy and convert some of it into the chemical energy. Some of the light is utilized to split water into oxygen and hydrogen. This splitting of water is called photolysis (photo= light, lysis= to break). Oxygen which is produced during photolysis is released in the environment whereas hydrogen together which CO2 is used in building glucose. Within the chlorplast, chlorophyll and the other pigment molecules form highlyorganized assemblies called photosystems. The conversion of light energy into chemical energy in these photosystems produces two energy rich compounds. These are: (i) NADPH2 (Nicotinamide Adenine Dinucleotide Phosphate) (ii) ATP (Adenosine Tri-Phosphate)


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NADP, which already exists in the chloroplast reduces into NADPH2 by accepting hydrogen ion released from splitting of water. NADPH2 NADP + H++e(In cell) (From water) (Reduced form) Another compound already present in the cell is ADP (Adenosine diphosphate) which combines with phosphate group by using light energy to form ATP (Adenosine tri-phosphate). Light energy ADP + P ATP Enzyme Reduction and oxidation are two important chemical concepts which help us to understand the terminology of the electron transfer chain. Reduction is the addition of electrons to a substance. In biological systems this addition of electrons is usually brought about by the addition of hydrogen or the removal of O2. Oxidation is the removal of electrons from substance. ATP and NADPH2, both are energy rich compounds. They provide energy for the conversion of CO2 into carbohydrates during dark phase of photosynthesis. Fig: 9.6 Photosynthesis consists of light-dependent and light- independent reactions 2. Dark reaction: Dark reaction is also called light independent reaction because light energy is not captured during this phase. Only ATP and NADPH2, which are synthesized during light reaction, provide energy to synthesize glucose by fixing CO2 and H2O. Fixation of CO2 and its conversion into glucose occurs in the chloroplast by means of a series of reactions known as Calvin cycle or dark reactions. Glucose molecules thus formed at this stage are stored as starch in the chloroplast. Melvin Calvin a scientist received a Nobel prize in 1961 on determining the dark reaction.

Experiment No. 1 Is chlorophyll necessary for Photosynthesis ? Since it is not possible to remove chlorophyll from a leaf without killing it, so it becomes necessary to use a leaf where chlorophyll is present only in patches. Such a leaf is known as variegated leaf and a plant with such leaves is used in this experiment. For destarching the leaves, the potted plant is kept in a dark place for a couple of days and then exposed to daylight for a few hour. The leaf is then removed from plant. Its out line is carefully drawn to note the position of presence or absence of chlorophyll on it. Now iodine is applied to the leaf to test for the presence of starch. (Startch whenever come in with iodine turns blue). This test shows that only those parts which were previously green turned blue with iodine while the white parts turned brown. This result indicates that starch is formed only in those parts of the leaf where chlorophyll exists (i.e. green parts). In other words, photosynthesis is not possible without chlorophyll. If this were possible the white parts of the leaf should have also given a blue colour with iodine.


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Fig: 9.7


To show that chlorophyll is necessary for photosynthesis

Experiment No. 2 Is light necessary for Photosynthesis? A potted plant is destarched by keeping it in the dark room for two days. It is then transferred to light. Two of its leaves are selected for the examination. One leaf is wrapped completely in black paper. The other leaf is also wrapped in black paper but an L-shaped part of the paper is cut out so that light can reach this part of the leaf through it. The plant is placed in the sunlight for 4 to 6 hours. The two leaves are now detached from the plant and tested for presence of starch. It would be observed that the leaf which does not receive any light is free of starch (remains brown with iodine). However, in the second leaf, light could through the L-shaped opening in the black paper. Only this 'L' shaped area turns dark blue while the other parts of the leaf remains brown. This shows that light plays a vital role in the manufacture of starch. Since starch is manufactured due to photosynthesis, light is essential for this process. Fig: 9.8 To show that light is necessary for photosynthesis Experiment No. 3 Is carbon dioxide needed for Photosynthesis? Two potted plants are destarched by keeping them in a dark room. They are watered properly during this period. Each pot is enclosed in a transparent polythene bag as shown in figure 9.9. A petri dish containing soda lime (potassium hydroxide) is placed in one of the pots to absorb any carbon dioxide present in the polythene bag. In the other pot a petri dish is placed containing sodium bi-carbonate solution which would produced carbon dioxide. The plants are then left in light for several hours. A leaf from each pot is detached and tested for starch. The leaf from the pot containing soda lime does not turn blue. Soda lime had absorbed any carbon dioxide present in the bag. The leaf from the other pot where carbon dioxide was being released by the sodium bicarbonates solution turns blue indicating the presence of starch. These results show that carbon-di-oxide is essential for photosynthesis. Fig: 9.9 To show that CO2 is necessary for photosynthesis Experiment No. 4 Is oxygen produced during Photosynthesis? A short stemmed funnel is placed over the shoot of an aquatic plant (Hydrilla) in a beaker of water as shown in fig. 9.10. A water filled test tube is inverted over the stem of the funnel. The funnel is placed in the beaker on s, to allow free circulation of water. The apparatus is kept in sunlight for some time. Bubbles of gas soon appear from the plant, rise and collect in the test tube. When sufficient gas has accumulated the test tube is removed. A glowing match stick is inserted in the tube. The match stick burns with a flame showing that the gas is rich in oxygen. It is clear from this experiment that oxygen is evolved during photosynthesis. Fig: 9.10 To show that Oxygen is set free during photosynthesis 9.3.5 Factors affecting the rate of photosynthesis: The rate of photosynthesis is affected by a number of factors. Such as light intensity, CO2 concentration, temperature and inorganic ions.


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Light intensity: The rate of light reaction will depend on the light intensity. The brighter the light, the faster will water molecules split in the chloroplast. Fig.9.11 shows that an increase in light intensity does indeed speed up photosynthesis, but only up to a point. Beyond that point, any further increase in light intensity has only a small effect. This limit on the rate of increase could be because all available chloroplast are fully occupied in light absorption. So, no matter how much the light intensity increases, no more light can be absorbed and used. Fig: 9.11 Light intensity and rate of photosynthesis Temperature: The dark reaction will be affected by temperature. A rise in temperature will increase the rate at which CO2 combines with hydrogen to make carbohydrate. Thus rate of photosynthesis increases with the increase in temperature within optimum limits. Carbon dioxide concentration: There is only 0.03% of CO2 in the air. Shortage of CO2 is an important limiting factor and slows down the rate of photosynthesis. Experiments show that an increase in CO2 concentration enhances the rate of photosynthesis. The stomata in a leaf may affect the rate of photosynthesis according to whether they are open or close. At low concentration of CO2 inside the leaf, the stomata will open. 9.3.6 Most of life forms are dependent on photosynthesis: The process of photosynthesis is of prime importance because all the living organisms on this earth are dependent on plants for food and O2, they produced. The photosynthesis is the only process which can fix atmospheric CO2 into organic compounds to produce bio-molecules. Therefore, plants are also called producers of ecosystem. Thus, they are the direct or indirect source of food for all the nonphotosynthetic life on earth. Plants through photosynthesis keep carbon and oxygen cycle going on and thus maintain them in balance. During photosynthesis they fix CO2 and release oxygen in environment. Animals use O2 in respiration and release CO2 back into atmosphere. One of the property of CO2 is that it absorbs heat of sun. If CO2 accumulates in the atmosphere, the environmental temperature would rise and our earth will warm up. Photosynthesis keep on using CO2 has an indirect cooling effect. 9.3.7 Mineral requirement in plants: CO2 and H2O are not the only nutrient material needed by a green plant. These two compounds provide only three elements, C, H, and O, but plants require more elements for the composition of their molecules, e.g. Nitrogen (N) is always present in amino acids, the building- block units of proteins which are essential components of protoplasm, some amino acid also contain sulphur (S). Phosphorous is present in ATP, nucleic acid and many other important compounds. Chlorophyll, essential pigment of photosynthesis contains magnesium while cytochrome important compound in electron, transport, contain iron. Plants absorb these elements in the form of different compounds from soil through their roots. Table 9.1: Important minerals required by plants Element Function Nitrogen (N) Structural components of amino acids, many hormones and co-enzymes etc.


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Magnesium (Mg)

Structural component of chlorophyll, co-factor for many enzyme involved in carbohydrate metabolism, nucleic acid synthesis and the coupling of ATP with reactions.

9.3.8 Importance of chemical fertilizers in Agriculture: Inorganic fertilizers help to replace the mineral ions consumed from the soil by successive production of crop. Usually three elements are added to the soil, by fertilizer in the inorganic form, are nitrogen, phosphorous and potassium, since these are the ones, which are mostly depleted by-the growing crop continuously. Modern commercial inorganic fertilizers are often designated by their N-P-K percentages e.g. the widely used garden fertilizer called 5-10-5 contains 5% N, 10% P and 5% soluble K by weight. Nitrogen is also added to the soil in the form of ammonium nitrate or ammonium sulphate. Phosphorous and potassium are added in the form of super phosphate and potassium chloride, respectively. 9.4 SPECIAL MODES OF NUTRITION Plants, usually being autotrophic, are directly or indirectly the source of food for all organisms on this earth. There are some special plants which cannot manufacture their own food and are wholly or partially dependent upon other plants or animals. Such plants are known as heterotrophic plants. Depending upon their special mode of nutrition, they can be divided into the following four types. 1. Parasites 2. Saprophytes 3. Insectivores 4. Symbionts. 1. Parasites: These are entirely or partially dependent upon autotrophic plants for their food supply. They grow on the stem or branches of the host rather than in soil. An important feature of these plants is that they have special roots known as haustoria which absorb ready made food from the host plant. These roots come in with the xylem and the phloem tissues after penetrating the stem and continuously absorb water and salts from their hosts. A well known parasitic plants is cuscuta. It is a total parasite; its weak and yellowish stem twines around shrubs and the branches of host trees. Fig: 9.12 Cuscuta—A parasite plant 2. Saprophytes: These plants have no chlorophyll and derive their food from dead organic matter. Some flowering plants like monotropa and neottia are also saprophytic in nature. These plants are found in thick jungles where sunlight cannot reach the ground and the soil is rich in decomposing organic matter. As there are no root hairs in these plants they cannot draw their nourishment from the soil. The roots of these plants develop in association with a special type of fungus. A part of the hyphae of this fungus enters the roots of these plants. These hyphae thus serve as 'root hairs' and help in the absorption of the food from the dead organic matter. Fig: 9.13

Monotropa.—A saprophyte

3. Insectivores: These plants are found in marshy areas of many countries. These marsh lands are deficient in nitrogen compounds and nitrates. To make up for this deficiency


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of nitrogenous compounds in their bodies, such plants feed on insects. They attract insects with their peculiar shape, colour and nectar and then trap them inside their modified leaves. The prey is killed, digested by enzymes and finally absorbed. The insectivorous plants can make their food by photosynthesis because of chlorophyll in their leaves and can survive without eating insects. However the insect-fed plants are stronger and healthier. They bear more flowers, fruits and seeds. Pitcher-plant is a common insectivore. It is found along Eastern Himalayas. In this plant the lamina of leaves is modified into an elongated pitcher with a lid at the top. It is here that insects are trapped. The leaf base becomes flat and behaves like leaf lamina. It is green due to the presence of chlorophyll. The petiole is twisted and curved to keep pitcher in straight position. Fig: 9.14 A leaf of a pitcher plant with pitcher 4. Symbionts: An association of two organisms in which both the partners get benefits is called symbiosis. For example, the association between nitrogen-fixing bacteria and roots of leguminous plants is symbiosis. Lichens are another example of symbiosis. Lichens are formed by association of a fungus and an alga so, they are modified organisms. The fungus provides shelter and water to the alga. The alga makes food by photosynthesis. Fig: 9.15 Symbionts: A lichen is an association of an alga and a fungus. The alga produces food; the fungus may provide protection and moisture. 9.5 NUTRITION IN ANIMALS Animals cannot manufacture their food from simple inorganic substances so they have to obtain' organic molecules from then-environment in the form of food. Such a way of nutrition is called animal like nutrition or holozoic nutrition. As animals obtain their food from other organisms, this type of nutrition is also called heterotrophic nutrition. According to their type of nutrition animals are of many types: (1) Carnivores (2) Herbivores (3)Omnivores (4) Frugivores (5) Insectivores (6) Parasites (7) Saprobes 1. Carnivores: This type of nutrition in which animals feed upon other animals is called carnivorous nutrition. Such animals are called carnivores. For example cat, dog, etc. Canine teeth of carnivore mammals are strong, long, sharp and pointed for tearing flesh of other animals. 2. Herbivores: In this type, animals use plants as their food. For example, horse, cattle, deer, etc feed upon leaves and grass. Such animals are called herbivores. They do not have canines. Many birds such as sparrow, parrot, etc. are also herbivores. 3. Omnivores: It is the mode of nutrition in which animals feed upon flesh as well as plants. Man, cockroach etc. fall into this category .These organisms are called omnivores. 4. Frugivorea: Animals like parrot, etc which feed on fruits like guava, figs etc. are frugivores and this type of nutrition is called frugivorous.


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5. Insectivores: In this type nutrition, animals feed upon insects. For example wall lizard and frog feed upon-a-variety of insects. Such animals are called insectivores. 6. Parasitic: A parasite lives in close association with the other living organism called host for obtaining its food. Organisms with this type of nutrition are called parasites. The relationship is advantageous to the parasite but harmful to the host. Some parasites live on the external surface of their hosts. They are called ectoparasites e.g. mosquito, lice, etc. They obtain their food from the surface of the host. Others live inside the bodies of their hosts. They are called endoparasites e.g. tape worms and round worms in the intestine of vertebrates. They obtain nourishment from inside the body. 7. Saprozoic: The organisms who obtain food from dead organisms are called saprobes and this type of nutrition is called saprozoic. Saprobes secrete the enzymes out side their bodies, on the food to digest it and then absorb it in the fluid form. Fungi and many bacteria fall in this category. 9.6 NUTRITION IN MAN 9.6.1 Constituent of food: Food is a set of chemicals that is basically required for growth and for obtaining energy. Moreover, food is needed to make enzymes for various metabolic processes. The food which animals, including humans, take in consists of the following components or nutrients. (1) Carbohydrates (2) Fats (3) Proteins (4) Vitamins (5) Minerals (6) Water 1. Carbohydrates: These are the fuel of the body because they are the most direct source of energy. Common examples are starch, sugars, etc. The most common simple sugar is grape sugar called glucose. It is the most readily available source of energy. 2. Fats: Fats belong to a group of organic compounds called lipids. Fats are high energy food. They provide double amount of energy upon oxidation, in contrast to the same quantity of carbohydrates. We obtain fats from animal sources e.g. ghee, butter, cream, fish oil etc, as well as from plant sources e.g. mustard oil, soyabean oil, peanuts etc. Animals store fats beneath the skin and around some visceral organs. Besides serving as source of energy they insulate the body and protect internal organs. They also serve as building material of protoplasm and membrane systems. 3. Proteins: Proteins are the building materials of protoplasm. They are obtained from meat, pulses, milk, cheese, dry fruits, etc. They consist of smaller units called amino acids. Proteins are required for growth, repair, defence of body, clotting of blood, etc., the deficiency of proteins in diet especially that of essential amino acids containing proteins, severely affects such functions. They are structure building compounds which make many body structures like hair, nails, muscles, etc.


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4. Minerals: Minerals are ionic substances which are required in metabolic activities of the body. They do not provide us energy but ensure proper growth and functioning of the body. Some important minerals are described below: Calcium: It is obtained from milk, eggs, fruits, and cereals. It strengthens the bones and teeth. It also helps in muscular contraction, blood clotting and conduction of nerve impulse. Iron: It is found in meat, liver, eggs, apple, spinach and other vegetables. It is used in synthesis of haemoglobin and myoglobin in blood and muscles, respectively. Phosphorus: It is found in milk, eggs, meat, vegetables etc. It is required for bones, teeth, formation of plasma membrane, nucleic acids, and ATP. 5. Vitamins: Vitamins are organic compounds which are needed in minute quantities for proper growth and development of the body. Plants can synthesize all vitamins from simple substances but animals have to obtain them through their diet. There are different vitamins which are denoted by letters of the alphabets such as A, B, C, D, E, K. They are classified as fat soluble vitamins e.g. A, D, E, K and water soluble vitamins e.g. B, C. Fat soluble vitamins can be stored along with, fat but water soluble vitamins cannot be stored so we require continuous intake of them. Table 9.2 shows different vitamins alongwith their sources, their deficiency disorders and characterization of disorders. Solubility

Table: 9.2 Vitamins and their functions Name of Sources of Characters Vitamin vitamins of disorder Vitamin A

Vitamin D

Fat soluble vitamins

Vitamin E


Fish-liver oil, animal liver, milk, cheese, fresh green vegetables. Fish-liver oil, butter, egg yolk, milk. Also made by action of sunlight on skin.

Plant oils, green leafy salad etc.

Essential for vision, growth and functioning of skin, etc. Bones remain soft and ultimately become deformed. In adults bones become painful and can be fractured easily. Few deficiency effects are noticed in adults. Severe deficiency in infants may cause high rate of destruction of

Disorders caused by lack / deficiency Dry cornea, dry skin poor night vision. Rickets (decrease in absorption of calcium and phosphorus in intestine).

Anemia

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Vitamin K

Water soluble vitamins

Vitamin B Complex Vitamin B1 Vitamin B2 Nicotinamide

Vitamin C

Dark green leafy vegetables. Made by bacteria in intestine. Husk of wheat grains and brown rice. Leafy vegetables, fish, eggs. Meat, fish, milk, eggs. Citrus fruits and green vegetables.

RBC. Prolong clotting time excessive bleeding Wasting of muscles; circulatory failure and paralysis Sore mouth, eyes and skin Diarrhea, dermatitis and mental disorder Bleeding from gums, wounds fail to heal

Blood does not clot

Beri Beri

Sore Pellagra

Scurvy

6. Water: Water makes up nearly 70 percent of the total body mass. It is required as solvent in most of the metabolic activities of the body. It also helps in the absorption and transportation of the digested food. It helps plants in photosynthesis for intake of minerals from the soil and in movement of food. 9.7 DIETARY FIBRES (Roughage) Dietary fibre or roughage is made up of the indigestible cell walls of plant cells that we take in our food such as fruits, vegetables. It provides bulk to the food in the intestine by retaining water. It also stimulates the gut for peristaltic movement which makes the age of food easier through the gut for defecation. Absence or shortage of dietary fibre in food may cause constipation or intestinal disorders. 9.7.1 Nutrition and food technology: We eat food in order to obtain energy for the maintenance of life and also to provide raw materials to build and repair the body. Thus there is a continuous need of food. Unfortunately, the production of food is seasonal and not uniform throughout the world. In order to ensure a continuous supply of food, some of it must be preserved and stored for later use. Food is destroyed either by the growth of micro-organisms such as bacteria, fungi or due to the enzymes of the cells of food. Man knows since the ancient times, the methods to preserve the food but these methods were not effective in preserving food for longer time. The nutritional value and taste were considerably lost in food preserved through such traditional methods. With the help of modern science, various methods have been developed to preserve the food for longer period of time without affecting its nutritional value and taste. Some of the important methods are as follows: 1. Pasteurization: It was discovered by Louis Pasteur to prevent milk from turning sour. You all know very well that milk is boiled after purchasing it from milk- man. Increase in


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temperature of milk up to the boiling point, kills most of the germs (bacteria) present in it thus milk can be kept longer. In the absence of boiling, it turns sour very quickly. The modern way of milk pasteurization comprises of heating to 71 °C and then immediate cooling. As a result most of its bacteria are either killed or if survive, their growth is retarded so the milk can be preserved for few days. 2. Refrigeration: Refrigeration is another way of preserving food. In this method food is kept at very low temperature at -30°C to -40°C. Due to very low temperature the bacteria are either killed or their growth is retarded. Now-a-days, food quickly freezes (-18°C) in about 30 minutes. It renders taste and texture of the food. 3. Dehydration: It is the oldest method of preserving food by dehydration. Although drying of food does not kill micro-organisms, it preserves the food as it makes water unavailable to micro-organisms which requires it to grow and multiply. Dried food is easily stored and transported due to its light weight. However, it often brings about a change in texture and taste of the preserved food. 4. Canning: In this method, food is adequately cooked and then sealed while hot in a sterile, metallic and air tight container. Heating kills the microorganisms as well as inactivates the enzymes. HEALTH PROBLEMS RELATED TO NUTRITION The problems related to nutrition are as follows. 1. Under-nutrition 2. Mal-nutrition 3. Over-nutrition 1. Under-nutrition: It is a problem of poor countries of the world where there is insufficient food for the people. Famine stricken countries such as Ethiopia are facing this problem. Under-nutrition especially affects the children. Due to insufficient food, their physical as well as mental growth are severely affected. Such children or persons This condition is called marasmus. Fig: 9.16 A child is suffering reduce to a skeleton only. 2. Mal-nutrition: It refers to a diet missing in one or more basic nutrients. It can affect person of any age or group. It can badly affect the pregnant women and infants. It has been noticed that mal-nutrition is the major cause of death among the children upto the age of five in the world especially in developing countries. Fig : 9.17 Effects of malnutrition (Girls of the same age) In Africa and Asia, due to poverty and famine, the diet is usually deficient in proteins and carbohydrates. Deficiency of protein in dite increases susceptibility to diseases besides retardation in growth. 3. Over- nutrition: It is observed in developed countries where people take excess nutrients. Obesity is the most common disorders due to over-nutrition. Obesity is caused by excessive consumption of refined carbohydrates and fats.


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Balanced diet: A balanced diet contains adequate amount of nutrients. It helps in proper growth, metabolism, and maintenance of good health. Unfortunately despite extensive research, it is not yet possible to say exactly how much of each type of food a person must take in order to satisfy all of its requirements. The problem of doing this is complicated by the fact that the body's food requirements vary according to age, body size, sex, occupation, and health. For example children need more food for their proper growth. Youth on the other hand need more food than elderly people because of their active physical work. It has been recommended that an average adult healthy person requires the necessary energy 50 percent from carbohydrate, 40 percent from fats and 10 percent from proteins. Fats are necessary in diet as they contain fat soluble vitamins as well as fatty acids. It is also recommended that adults should eat at least 1gm of protein per kg of body weight per day. How ever infants should be given 2gm per kg from birth to six months. It is further suggested that 60 percent of daily intake should consist of animal proteins since this contains more essential amino acids. Raw food (100g) Rice Eggs Butter Milk (Mother) Milk (Cow) Sugar Beef Fish Mutton Beans Orange Apple

Energy (K.cal) 360 163 716 60 65 387 183 176 153 35 45 58

9.9 DIGESTION IN MAN Man, like other animals takes food that consists of complex and larger molecules. For example, imagine your food when you take a chicken sandwich. The bread of the sandwich contains starch which is insoluble and chemically different from glycogen or glucose. Similarly fat/oil in the butter of the sandwich are also insoluble. Also the proteins of sandwich are useless to you in the form they are eaten. Thus such large indiffusible food molecules must be broken into smaller diffusible molecules so that they can be absorbed by the cells either to provide energy or to serve other purposes.- This process is called digestion. This entire process takes place inside a long, coiled, muscular tube of varying diameter. This tube called alimentary canal, opens at the anterior end of the body through an opening called mouth and at the posterior end through another opening called anus. Ingestion takes place at mouth and egestion at anus. Alimentary canal is associated with a number of glands like salivary glands, liver and pancreas which secrete digestive juices containing special chemicals called enzymes to bring about the chemical digestion of food. The alimentary canal together with its glands are called the digestive organs. The alimentary canal is differentiated into buccal cavity, oesophagus, stomach, small intestine and large intestine. The process of digestion involves following different stages; 1. Ingestion 2. Digestion 3. Absorption 4. Assimilation 5. Egestion


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9.9.1 Ingestion: The process of taking in of food into the mouth or body of animal is called ingestion. In the mouth cavity also called buccal cavity or oral cavity, this food is cut down into smaller pieces with our teeth. This crushing of food make its swallowing easy, helps in mixing the saliva in it and makes the work of digestive juices (emzymes) easier and quicker. The process of breaking the food mechanically into smaller pieces is called mechanical digestion while the chemical break down of food into smaller chemical molecules is called chemical digestion which is brought about by enzymes. 1. Teeth: As stated above, teeth in our oral (mouth) cavity perform mechanical digestion. In both of our jaws, teeth are embedded in jaw sockets. We have two sets of teeth during life time. The first set of teeth, milk teeth appears at about 6 months of age. Later, about at the age of 7 years, the milk teeth gradually fell and are replaced one by one by permanent teeth. The maximum number of permanent teeth is 32. (i.e, 16 in upper, while 16 in lower jaw). Structure of tooth: Each tooth consists of three parts i.e. crown, neck and root. Crown is the part of tooth projected above the gum level. It is the biting or chewing surface of tooth. Neck is the part surrounded by gum while root is the part embedded in bone. The outer surface of crown is covered by a very hard white substance, the enamel. It is non-living and protects teeth besides giving lustrous appearance to teeth. The root as well as the portion inside the enamel is dentine. It is less harder than enamel. Inside the dentine, there is a cavity, the pulp cavity. It is filled by soft connective tissue called pulp. It also contains nerves and blood vessels that supply the growing tooth with food and oxygen. The root of each tooth is covered with another hard material called cement. The tough fibers of periodontal membrane attach the cement to the jaw bone so that each tooth is fixed firmly in socket. Fig: 9.18 Structure of a tooth Types of teeth: According to the shape and function following types of teeth are present in our oral cavity. i) Incisors ii) Canines iii) Premolars and iv) Molars. Molar: The molars are large strong teeth efficient at grinding food. Premolar: Also known as bicuspids, because of other two distinct edges grind the food. Incisors: These teeth have a chisel shaped, sharp cutting edge ideal for biting. Canines: The canines are sharp pointed teeth, Ideal for tearing food. Fig: 9.19 Types of teeth i) Incisors: The flat chisel-shaped teeth resent in front of oral cavity are incisors. They are eight in number, four in upper while four in the lower jaws. They are used in cutting. ii) Canines: Beside incisors lie canines on each side in both jaws. They are four in number and are pointed. They are used for tearing and pulling flesh. That's


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why they are very long and prominent in carnivores such as lion. Herbivore animals usually do not have canines. iii) Premolars: In both jaws each canine is followed by two premolars. They are 8 in number and each with two distinct edges. They are involved in grinding the food. iv) Molars: Premolars of each side of both jaws are followed by three molars. They are 12 in number. They also grind food. The last molar is called wisdom tooth. The arrangement of teeth can be represented by the following formula called dental formula. I2/2, C 1/1, Pm 2/2, M 3/3 It represents each type of tooth in half of the upper jaw and half of the lower jaw. 2. The causes of tooth decay and its prevention: Tooth decay refers to erosion of enamel and dentine. Its major reason is dental plaque which is a sticky substance consisting of food remains, mucus and bacteria. The plaque develops as a hard layer over teeth due to not brushing or improper brushing of teeth after each meal. It develops due to eating too much sweets such as candies, chocolates etc. The bacteria feed on left over sweet which is broken down to produce an acid that gradually destroys enamel forming a cavity in it.  Particles of sugary food get trapped in cracks in the teeth.  Bacteria feeding on the sugar form acids, which dissolve the enamel and dentine and hole starts forming.  There are nerves in the pulp cavity, so the tooth becomes very painful when hole reaches the pulp.  The infection can spread rapidly through the pulp cavity and may form an abscess at the root of the tooth. Fig: 9.20 Tooth decay If this decay is ignored, the erosion penetrates deep to destroy dentine. This enables bacteria to infect pulp. This results in tooth ache and tooth is gradually destroyed. Tooth decay can be reduced by cutting down sugary diet and proper brushing with a fluoride tooth paste. Visit a dentist regularly for check up for healthier teeth. 9.9.2 Digestion: 1. Digestion of food in mouth: The process of mechanical and chemical digestion begins in mouth. The teeth grind the food while three pairs of salivary glands of oral cavity secrete saliva. It contains an enzyme called ptyalin which acts upon starch to break them partly into maltose (sugar). This masticated and partially digested food takes the form of a ball called bolus is then pushed into the oesophagus. Fig: 9.21 The human alimentary canal 2. Digestion of food in stomach: Stomach is a large bag-like, thick walled structure which stores food as it es down the oesophagus. Here food is digested chemically as well as mechanically. Internally, its walls contain gastric glands which secrete gastric juice which contains HCl and enzymes called renin and pepsin. HCl kills the germs present


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in food. It also softens the food. Renin helps to curdle milk in infants. Pepsin acts on proteins to break them into peptones. The thick walls of stomach churn up the food. After staying here for few hours, the food becomes a thick fluid-like chyme which is released bit by bit into the small intestine. Peristalsis: The movement of food from oesophagus and onward up to the anus takes place by means of an automatic movement or peristalsis (Fig: 9.22) of alimentary canal. Fig 9.22 Peristalsis 3. Digestion and absorption of food in small Intestine: Stomach is followed by a long, narrow tube called small intestine where the remaining process of digestion is completed as well as the absorption of nutrients from the digested food takes place. Its first part lying immediately after the stomach is duodenum which receives a common duct formed by the fusion of a duct coming from the gall bladder of the liver and another duct coming from the pancreas. Through these two ducts, the secretion of liver called bile and the secretion of pancreas known as pancreatic juice are poured simultaneously in the duodenum upon the acidic chyme which is coming from the stomach. Both of these secretions contain bicarbonate ions which first neutralizes chyme and then turns it alkaline. 4. Enzymes: Enzymes are chemical substance that work as catalyst in chemical reactions of a cell. These proteins are useful as they speed up chemical reactions without being used up by themselves. Enzymes performing the process of digestion are called hydrolytic enzymes. They are secreted by digestive glands. a) Liver: The liver is the largest gland in the body. It is reddish brown in colour. It is located in the abdomen underneath the diaphragm. For the process of digestion, it secretes an alkaline, greenish yellow juice called bile which is stored in a sac-like gall-bladder attached with it. There are no enzymes in bile. It contains some salts. Its most important salt is sodium bicarbonate. It also contains bile pigments. However, they are not involved in digestion. Bile helps in breaking down of larger molecules of fats into small droplets. This process is called emulsification. It makes the digestion of fats easier in the small intestine. b) Pancreas: It is a long, leaf-like organ situated between the duodenum and the stomach. Its secretion is called pancreatic juice. It is colourless and poured through the pancreatic duct into the duodenum. It contains sodium bicarbonate and many enzymes. Three important pancreatic enzymes are discussed below: i) Amylase: It breaks down starch into maltose. ii) Trypsin: It acts upon the proteins to convert at into smaller peptides. iii) Lipase: It breaks fat droplets into fatty acids and glycerol. 9.9.3 Absorption of food in small intestine: Duodenum is followed by ileum, the next portion of small intestine where the rest of the digestion is completed by the enzymes present in intestinal juices secreted by the glands present in the walls of small intestine itself. Its enzymes aminopeptidases and disaccharidases convert peptides into amino acids' and maltose/lactose/ sucrose into glucose, respectively. After the process of digestion of food is completed here, the digested food in the form of soluble molecules glucose, fructose, amino acids, fatty acids, glycerol, etc. is absorbed into the body through very fine, finger like projections called villi present on the internal walls of ileum.


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Each villus is about 1mm long. There are about 5 million villi in the ileum. Due to villi, the internal surface area of ileum has estimated to be 30 square meters for absorption of food. The villi greatly increase the internal surface area of the ileum. Inside each villus, there is a dense network of blood capillaries and a single lymph vessel or lacteal. Both blood capillaries and lacteal absorb the digested food. Nutrients other than fatty acids diffuse through the surface cells of villi and are taken into the blood flowing in capillaries of villi. These capillaries together to form a larger blood vessel called the hepatic portal vein which carries the absorbed food to the liver. Some fatty acids, after they are absorbed by surface cells of rilli, recombine to form fats which are ed onto the other side into lacteal rather than blood capillaries. Lacteals of villi together to form lymph vessels which finally deliver the fats into blood stream through lymphatic system. Fig: 9.23 Structure of Villus Table: 9.4 Digestive juices, their sources. secretion / enzymes and the action. Secretion/ Action Name of Source Enzyme digestive juice Saliva Salivary glands in Ptyalin Breaks down oral cavity starch into maltose. Gastric juice

Gastric glands in stomach

HCl Pepsin Renin

Germicidal, activates pepsin, breaks down proteins into peptones. Curdles milk.

Bile

Liver

Nil

Turns acidic chyme alkaline and emulsifies fat.

Pancreatic juice

Pancreas

Trypsin

Breaks down proteins into peptides.

Amylase

Breaks down starch into maltose.

Lipase

Breaks down fat droplets into fatty acids and glycerol.

Amino peptidase

Breaks down peptides into amino acids.

Disacch-aridase

Breaks down maltose and other disaccharides into glucose.

Intestinal juice

Intestinal glands in small intestine


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9.9.4 Assimilation of digested food: The soluble nutrients after being absorbed are transported through the blood to each and every cell of the body. Depending upon the requirement of the cell, this food can be used either to build new protoplasm or to obtain energy to perform various activities. The incorporation of food by a cell in its components is called assimilation. Our food consists of different components. Some of its components | such as roughage remain undigested. This undigested food along with considerable quantity of water is ed from the ileum into the large intestine. It is a wider tube but shorter in length than small intestine. It consists of caecum, appendix, colon and rectum. In the large intestine reabsorption of water occurs so the undigested food first becomes paste-like and then slightly harder. Meanwhile, the intestinal bacteria cause fermentation of the undigested matter which is now termed as faeces. 9.9.5 Egestion: The faeces are stored in the rectum, the last portion of alimentary canal where it is stored for the time being and then egested outside the body through a terminal opening called anus. 9.10 DISORDERS OF GUT Proper functioning of the digestive system or gut needs regular intake of balanced and germ free diet. However, some times due to the intake of contaminated food, some disorders of gut may develop. Some disorders of gut are discussed below: 1. Vomiting: Whenever we take food containing harmful or poisonous substances, the contents of stomach are expelled out through the mouth by antiperistaltic movements. This process is called vomiting. It may occur when we over eat and helps to expel out the food from the stomach giving us some relief. The sensation, just before vomiting, that the food in the stomach wants to come out is called nausea. There are a number of other reasons for vomiting such as peptic ulcer, appendicitis, many other diseases, psychological or emotional problems, travel sickness, bad smells, pregnancy etc. 2. Diarrhoea: Diarrhoea refers to the condition of large number of watery motions. It is usually caused by infection of colon or food poisoning. Due to continuous diarrhoea, the body can lose large quantity of water which could be fatal if not rehydrated. Infants and young children are easily dehydrated due to diarrhoea. In case of diarrhea, they must be given continuously solution of ORS (Oral Rehydrated Salt). The physician must be consulted immediately to diagnose and treat the patient. 3. Constipation: This is just reverse of diarrhoea. It is the condition in which there is infrequent or difficult ing of dry, hard faeces occurs. It is said to be the mother of all diseases. It is a disorder of large intestine which absorbs excessive amount of water from undigested food. It can be avoided by drinking lot of water and eating more fibre containing food.


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4. Appendicitis: It is the inflammation (burning, painful sensation) of the appendix associated with vomiting and abdominal pain. It could be due to obstruction of the appendix either by faeces or worms which cause localized swelling Pain in right side of lower abdomen. In such a case, physician must be consulted irnmediately for diagnosis and treatment . If the condition remained ignored for some time, the appendix may burst cavity that could be extremely fatal for the patient. 5. Enterobiasis: Thread worms cause a disease called enterobiasis. These are minute, thread like worms which live in the large intestine of man. At night time, the female worms come down and lay eggs at the preanal region. It produces severe itching around the anus. Upon scratching the anus, the microscopic eggs are transferred on fingers and nails. Such contaminated hands can cause reinfection of the same person or others who take food or drink contaminated with the eggs. Proper treatment and development of hygienic habits can over come the thread worm infection.


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                


SUMMARY The intake of nutrient by living organisms is called nutrition. Living organisms can be divided into two groups on the basis of their modes of nutrition i.e. Autotrophs and heterotrophs. The heterotrophs eat food which contain bio-molecules like carbohydrates, proteins, fats, vitamins, minerals and water. Simple sugar, starch and glycogen belong to a group of compounds called carbohydrates. Proteins are the polymers of nitrogenous monomers called amino acid. Proteins are building as well as biocatalyst molecules of the body. Most of the plants prepare their food by the process of photosynthesis. In this process a plant can build sugar by taking CO2, H2O in the presence of chlorophyll and light. During light reaction photolysis of water and photophosphorylation occur as a result of it O2, ATP and NADPH2 molecules are formed. Solar energy is converted into chemical energy in the form of ATP and NADPH2 which is utilized during dark reaction for the fixation of CO2. The Dark reaction is light-independent phase where glucose and finally starch is synthesized. Natural and artificial fertilizers are the source of mineral nutrients for plant. Although majority of plants are autotrophs, some plants like, parasites, saprophytes, insectivores and symbionts are partially or totally heterotrophs. Animals can not prepare their food from simple inorganic substances and hence are all heterotrophs. Fats provide double amount of energy than carbohydrates. Minerals ensure proper growth and functioning of the body. Water is biological solvent. Malnutrition develops due to intake of inappropriate quantities of food. Vomiting occurs due to antiperistalsis.


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EXERCISE 1. Fill in the blanks with appropriate : i) Ready source of energy in the cell is________ . ii) Chemical name of cane sugar is_______ . iii) The process of conversion of light energy into chemical energy is called___________. iv) _________and__________light is absorbed by reaction centre during photosynthesis. v) Another name of dark reaction is____________. vi) Deficiency of Vitamin B causes___________. vii) Indigestible cell walls of plant cells is called_________. viii) Adults should take_______gm protein per kg of their body weight per day. ix) The part of teeth projected above the gum level is called________ x) Starch breaks into maltose through the action of enzyme_______ 2. Write whether the statement are true or false: i) Glycogen and starch are the polymers of glucose. ii) Fats and oils are the consendation products of amino acid. iii) ATP formation is called phosphorylation, This process takes place during dark reaction, iv) ATP and NADPH2 provide energy for the fixation of CO2 during dark reaction. v) Widely used garden inorganic fertilizer is called 6-12-6. vi) Vitamin K deficiency is related to abnormality in the proccess of blood clotting. vii) Calcium is required for the formation of blood. viii) Condition in which a person is reduced to the skeleton due to insufficient diet is marasmus. ix) Carbohydrates are digested in stomach. x) Herbivore animals do not have incisors. 3.


ii) iii) iv) v) vi) vii)

Organisms which use inorganic material from environment as nutrient are: (a) Saprophytes (b) Parasites (c) Autotrophes (d) None of them Food of heterotrophs consists of (a) Proteins (b) Fats (c) Carbohydrates (d) All of them Glycogen is a molecule that belongs to (a) Carbohydrate (b) Fats (c) Protein (d) Vitamins CO2 from air is taken by leaf through (a) Stomata (b) Epidermis (c) Mesophyll (d) Lenticle Cuscuta is a leafless plant, it is (a) Total parasite (b) Partial parasite (c) Saprophyte (d) Symbiotic Animals who feed upon dead organic matter are (a) Parasites (b) Saprozoic (c) Herbivores (d) Omnivores It is considered as building material of protoplasm. (a) Lipids (b) Carbohydrates(c) Vitamins (d) Proteins,


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viii) ix) x)

Following are not fat soluble vitamins (a) A and D (b) E and K (c) B and C (d) D and E Rickets develops due to the deficiency of vitamin (a) A (b) B (c) C (d) D Which of the following secretion lacks enzyme (a) Saliva (b) Gastric juice (c) Bile (d) Pancreatic juice.

4. Write detailed answers of the following questions: i) Why life on earth is completely dependent on plants and how? ii) Why leaves are the major sites of photosynthesis? iii) Describe some special modes of nutrition found in plants. iv) Write a note on chemical fertilizers of plants? v) What is roughage and how it is related to our health? vi) What is mal-nutrition? Why is it a health problem? vii) Write a detailed note on balanced diet. viii) State and explain the process of mechanical and chemical digestion in man. ix) What is tooth decay? x) Explain the role of liver in the digestion. xi) What are villi? Explain their role in increasing the absorptive surface of intestine. 5. Define the following : i) Nutrition ii) Limiting factor iv) Autotrophs v) Heterotrophs vii) Balanced diet viii) Dietary Fibre x) Enzyme xi) Peristalsis 6.

iii) Photosynthesis vi) Saprophyte ix) Pasteurization xii) Appendicitis

Distinguish between the following: i) Autotrophs and heterotrophs ii) Light and Dark reaction iii) Protein and carbohydrate iv) Carnivore and Herbivore v) Digestion in stomach and digestion in intestine


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Chapter 10 RESPIRATION

One can survive for weeks without food, for days without water but without oxygen one just cannot survive after a few minutes. To keep the candle of life burning exchange of O2 and CO2 inside and outside the body is a must. Learning objectives:  Definition and significance of respiration.  ATP and its importance.  Respiration and breathing.  Aerobic and anaerobic respiration.  Combustion, respiration, photosynthesis.  Gaseous exchange in plants and animals.  Human respiration.  Effects of smoking on respiratory system; Respiration may be defined as, “a process that liberates chemical energy from organic molecules when oxidized." These organic molecules are the food substances which the organisms obtain from the environment or synthesize themselves. Nutrition is also a process of acquiring food. It contains energy. Food molecules are bonded chemically, they require some energy for bonding. Whenever energy is required for any metabolic activity the food is oxidized within the living cells by the help of enzymes. These bonds are broken and the energy is released. This process is known as respiration. The energy obtained through respiration is utilized to perform all the body functions, like cell division, growth, movement etc. 10.1 ADENOSINE TRIPHOSPHATE (ATP) FORMATION All the living organisms from bacteria to human beings are always in need of energy. They cannot survive without it. As the cells can use energy only in the form of ATPs so they are often called currency of energy and to carry out the continuously going on metabolic activities a constant supply of ATP molecules is always needed. ATPs are synthesized in mitochondria. Each ATP molecule, chemically, consists of an organic component adenine linked to a ribose (5 carbon sugar) to form adenosine to which is attached a chain of three inorganic phosphate groups. An ATP molecule is the instant source of energy within the cell. It supplies energy to every energy consuming process anywhere in the cell. Fig: 10.1 Structure of ATP Chemically ATP is hydrolysed to ADP by enzyme ATPase releasing a phosphate and liberating 30.6 KJ (7.3 Kcal) of energy. An ADP is like a discharged battery. When the energy is made available, by oxidation of food, ADP takes this energy to be converted to ATP that is to say that it becomes charged once again. A mole of glucose has 2827 KJ (673Kcal) of energy which is released during oxidation. About 1100 KJ (263 Kcal) are available in the form of ATPs whereas the rest is lost as heat energy. Fig: 10.2 ATP- ADP Cycle


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10.2 RESPIRATION AND BREATHING At one stage when our knowledge about cell metabolism was not adequate, respiration was considered as only the process of inhaling oxygen and exhaling carbon dioxide. Now, however, it is clearly understood that respiration is a complex two step process, breathing and cellular respiration or simply respiration. i) The breathing or gaseous exchange, takes place through the respiratory surface by diffusion, either directly or through some transport medium like blood and does not involve any release of energy. ii) Cellular respiration on the other hand is the oxidation of food taking place within the cells by the help of oxidative enzymes resulting in the release of energy. Thus both the steps of cellular respiration and breathing go together as two separate steps but integral processes for the release of energy. 10.3 CELLULAR RESPIRATION Cellular respiration also called tissue respiration takes place within the cell. It is the actual process which liberates energy. It usually requires oxygen and is called aerobic respiration. Sometimes it takes place even in the absence of oxygen and is called anaerobic respiration. 10.3.1 Aerobic respiration: This is the usual mode of respiration in plants and animals. It takes place in the presence of free oxygen, oxidizing the food completely and releasing the maximum energy, 2827 KJ / mole of glucose. The end-products are carbon dioxide and water. No toxic substances are formed. Chemical equation; Glucose + Oxygen

Aerobic respiration

Carbon dioxide + Water + Energy (2827 KJ)

10.3.2 Anaerobic respiration: Anaerobic respiration also called fermentation, takes place in some bacteria, fungi and endoparasites. It takes place in the absence of free oxygen, hence, the food is oxidized partially, releasing, a small amount of energy (only 5% to 10% as compared to aerobic respiration). The end-products of anaerobic respiration in bacteria and fungi are ethanol (ethyle alcohol) and carbon dioxide, whereas in animals lactic acid is produced. Ethanol and lactic acid are toxic substances which may harm the organism. Chemical equation; In bacteria and fungi, Glucose

Aerobic respiration

Ethanol + Carbon dioxide + Energy (210 KJ)

In animals: Glucose

Aerobic respiration

Lactic acid + Energy (150KJ)

10.3.3 Importance of Anaerobic respiration: As stated earlier, anaerobic respiration takes place in some fungi, bacteria and endoparasites. Although it yields much less energy in comparison to aerobic respiration, it has an advantage that these organisms can survive without oxygen. Endoparasites especially the gut parasites respire anaerobically as no free oxygen is available.


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Fermentation: The anaerobic respiration of fungi and bacteria is commonly known as alcoholic fermentation because in the absence of oxygen glucose is broken down into ethyl alcohol and carbon dioxide. This fermentation process is commercially utilized in making alcoholic products (Beer, wine, vinegar etc), ripening of tea leaves and tobacco leaves, preparation of cheese, yoghurt and bread etc. Human muscle cells make ATP by lactic acid fermentation when oxygen is deficient. In the absence of oxygen, in muscle cells glucose is broken down into lactic acid. This occurs during prolonged heavy exercise, when sugar catabolism for ATP production sures the muscles supply of oxygen from the blood. Under these conditions the cells switch over from aerobic respiration to fermentation. The lactic acid that accumulates as a waste product may cause muscle fatigue and pain, but is gradually carried away by the blood to the liver where it is converted back to an energy releasing compound pyruvic acid and glycogen by the liver cells. 10.4 COMBUSTION, RESPIRATION AND PHOTOSYNTHESIS Combustion is the process of burning. Wood, coal, methane gas etc. are burnt in the presence of oxygen, producing carbon dioxide and water. It is accompanied with the release of energy. It is an exothermic chemical reaction. Cellular respiration can be compared to burning of fuel in which organic food (carbohydrates, fats and proteins) rich in carbon burns in the presence of oxygen, producing carbon dioxide, water and energy. When oxygen was discovered as the agent for combustion, it was known that the food is burnt within cells in the presence of oxygen. Respiration like combustion is a catabolic exothermic chemical process. However, the difference between the combustion and respiration is that the combustion takes place in one go, releasing the entire energy as the heat, which may be utilized or is lost into the environment. The respiration completes in several small steps. Each step is under the control of a specific enzyme, releasing energy in small amounts which can be stored in the form of ATPs. Fig: 10.3 Relation between cellular respiration and photosynthesis Photosynthesis, another metabolic: process, is just opposite to combustion. Combustion is a catabolic process, the photosynthesis is an anabolic process. In photosynthesis, organic substance is synthesized from carbon dioxide and water in the presence of sunlight energy and chlorophyll. The molecular oxygen is evolved as the by-product. Combustion is exothermic and releases energy, photosynthesis is endothermic and absorbs energy. Photosynthesis and respiration are the two metabolic reactions opposite to each other. Photosynthesis takes place only in the green parts of the plant body having chlorophyll, whereas respiration takes place in all the living cells of plants and animals. Mitochondria are the cellular organelles where respiration takes place while the organelles for photosynthesis are chloroplasts. Photosynthesis takes place during the day time only, where as respiration takes place day and nignt. In photosynthesis body weight is increases but in respiration weight decreases. Respiration is an oxidation reaction whereas photosynthesis is a reduction reaction. It can be well understood by comparing their chemical equations. Chemical equation; In respiration,


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Glucose + Oxygen


Mitochondria enzymes

Carbon dioxide + Water + Energy

In photosynthesis, Carbon dioxide + Water

Chloroplast Solar energy

Glucose + Oxygen

10.5 GASEOUS EXCHANGE Exchange of carbon dioxide and oxygen between the environment and organism is termed gaseous exchange. All living organisms exchange gases with the environment. This is necessary to allow the cells to obtain the gases needed for metabolic processes and to facilitate the removal of gaseous metabolic waste. Efficient gaseous exchange depends upon three conditions. Diffusion gradient, large respiratory surface area and a moist surface membrane. So that the gases can go into solution before they across. Gaseous exchange takes place in all organisms by diffusion directly or indirectly. 10.5.1 Gaseous Exchange in Plants: The gaseous exchange in plants takes place through the entire body surface and through the stomata. Except the root, the whole plant body is covered by a water proof cuticle to check the evaporation of water, but at the same time prevents gaseous exchange. The only means through which gases can be exchanged in stem and large roots are minute openings called lenticeles. Oxygen also enters and dissolved in water from the soil through root hairs. Due to their large numbers and having large surface area leaves are the main places of exchange of gases and it takes place through stomata. Stomata: Stomata (sing: Stoma) are pores in the epidermis of leaves and stems of plants. Each pore is bordered by a pair of modified epidermal cells called guard cells, which are (bean) shaped, containing chloroplasts and a large sap filled vacuole. The inner wall (the wall lining the pore) is thicker and less elastic than the outer wall. The opening and closing of stomata depends on changes in the fluid pressure of the walls. If water flows into the guard cells, they expand opening the pore. If the guard cells lose water, they straighten up closing the pore. Fig: 10.4 Structure and action of a stoma The timings of opening and closing of stomata depends upon the environment. Under natural conditions stomata open at day time and close at night. So light appears to be the main factor which initiates opening. Gaseous exchange in leaves: Leaves are the chief organs of gaseous exchange as the stomata are most numerous in the leaves, usually in the lower epidermis in dicotyledons. The grasses and other monocotyledons have stomata in both upper and lower epidermis. Diffusion inside the stoma: Once inside the leaf, the gases through the sub-stomatal chambers into the inter-cellular spaces of the mesophyll from where it diffuses into the cells. It dissolves in the cell sap and goes into solution for photosynthesis and respiration. 10.5.2 Gaseous Exchange in Animals Like plants all animals exchange gases for respiration. They take in oxygen from, the environment, (air or water) and expel carbon dioxide into the environment.


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There are marked differences in the oxygen content of air and water. A unit volume of air contains far more oxygen in it, than an equal volume of water. Thus an aquatic organism such as fish must a correspondingly much greater volume of water over its gaseous exchange surface than a terrestrial vertebrate es air in order to absorb sufficient amount of oxygen for its metabolic needs. Animals show a great variety of form and structure, but the functions of life are the same. All animals respire as it is the basic need of living organisms by which they get energy to do work. As the form of organisms becomes more and more complex, their functions also become complicated to achieve the maximum efficiency. Comparison of a sample of fresh water and air Air Water Density 1 77 1 100 Viscocity 210 ml/litre or 21% 10 ml/litre or 1% O2 Content Unicellular organisms like amoeba possess a large surface area to volume ratio, hence diffusion of gases takes place over the whole surface via the plasma membrane. In Poriferian and Cnidarians all the cells of both the layers are in with the water so each cell is able to exchange gases. Free living platyhelminthes acquire oxygen by means of diffusion through their body surface. This is facilitated by the flatness of the body which increases the surface area to volume ratio. Annelids possess a blood vascular system which contains the as gas carrying pigment haemoglobin. The oxygen diffuses through the body surface into the blood circulating under the skin, where it combines with the haemoglobin and is carried to all the parts of the body. The carbon dioxide is brought back by the blood diffuses out. Molluscs, arthropods, echinoderms and vertebrates have developed respiratory organs through which gaseous exchange takes place. These respiratory organs are gills, tracheal tubes, book lungs and the true lungs. Gills: Gills are respiratory organs of aquatic animals, which are in direct with the surrounding water. They exhibit a great variety of form but basically they share the same fundamental structure. Each gill has a number of membranous folds called lamellae, which are richly supplied with blood capillaries. Deoxygenated blood circulates through the gill capillaries, where gaseous exchange takes place: Fig: 10.5 Gills The oxygen of the surrounding water which enters through mouth and bathes the gills diffuses into blood and carbon dioxide of the blood diffuses out. The respiratory pigments help in diffusion and transport of the gases. Tracheal tubes: The Tracheal tubes are found in terrestrial insects, which form a network of ramifying troubles through out the body forming a tracheal system. It allows gaseous oxygen to diffuse in from the outside air directly to the tissues without the need of transportation by blood. This is much faster than diffusion of dissolved oxygen through the tissues and permits high metabolic rates.


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A number of paired holes called spiracles are present on the sides of thoracic and abdominal segments which lead air into branched tubes called tracheae. Each tracheae has a chitinous cuticle lining which prevents it from collapsing. In each segment the tracheae branch into numerous smaller tubes called Tracheoles which ramify among the body tissues ending blindly. Tracheoles lack a chitinous lining. At rest the tracheoles are filled with watery fluid through which gaseous exchange takes place in dissolved state. Since the O2 is transported directly to the body cells, insect’s blood is white lacking hemoglobin. Fig 10.6 Tracheal system of grasshoper Book lungs: Book lungs are pulmonary sacs found in terrestrial arthropods like scorpion and spiders. Each book lung consists of a compressed sac like cavity having numerous folds or lamellae which are attached to the inner side of the chamber and are arranged like the leaves of a book. Each lamellae is hollow where the blood flows, while the inter lamellar spaces are filled with the air, so that gaseous exchange takes place through the thin walls of the lamellae. Fig 10.7 Book Lungs Lungs: Lungs are the most advanced type of respiratory organs found in terrestrial animals and in those aquatic animals which breathe through the air. These are amphibians, reptiles, birds and mammals. The amphibians (frogs) have a pair of hollow sac like simple elastic lungs which hang into the abdominal cavity, Their inner surface is greatly folded, moistened with mucus and richly supplied with blood capillaries. Leading from each lung is a short tube the bronchus. The two bronchi to form the trachea which opens into the pharynx. The ventilation takes place by the up and down movement of the floor of buccal cavity. The reptiles have more complex internal foldings of the lungs. Ventilation occurs by the movement of the ribs. Bird’s lungs are small compact inelastic structures composed of numerous branching air tubes called bronchioles. Extending from bronchioles are large thin-walled air-sacs. The mammalian lungs though elastic are build on the same plan as of birds. They are remarkably efficient structures which fulfil the function of gaseous exchange with minimum water and heat loss. 10.6 HUMAN RESPIRATORY SYSTEM The human breathing system consists of a pair of lungs and established system of tubes for intake and removal of air through the nose. The Lungs are situated in the thorax, in a rib cage, the walls of which are formed by the ribs attached ventrally to the sternum and dorsally to the vertebral column, which intercostal muscles in between. The floor is made up by the diaphragm. Air is drawn into the lungs from nose, through a pair of nostrils into the nasal sacs. The nose and mouth are separated by the palate so that one can breathe through nose even when eating. The inside of the nasal cavity is moist and warm. It has mucus producing ciliated lining and numerous blood vessels close to the surface. The air is moistened and its temperature is adjusted as it es over these surfaces. At the same time it is also cleaned, as the dust particles and


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germs get stuck in the mucus and are propelled toward the pharynx by the cilia where they are swallowed or coughed out. The air the es into a long wind pipe, the trachea about 12cm long. Its upper part is called larynx or vice box which contains vocal cords. The opening of the larynx is called glottis having a cartilaginous flap like structure epiglottis which closes the glottis during swallowing of food and water. The walls of trachea are ed by incomplete rings of cartilages which keep it open all the time. Fig 10.8 The human gaseous exchange system The trachea branches into two bronchi which have almost the same structure as that of the trachea bur are smaller in diameter. Each bronchus enters a lung, where it splits and respilts into numerous branches. These branches are called bronchioles At the end of each bronshiole a bunch of tiny air sacs or alveoli, where the gaseous exchange takes place between air and the blood. The walls of the alveoli make the respiratory surface which is surrounded by the blood capillaries. Oxygen diffuses out into the blood and carbon dioxide from the blood difuse into the alveoli. 10.6.1 Ventilation: Ventilation means movement of air in and out. Breathing, one step of respiration, is often called ventilation. Breathing which takes by the movement of the chest, can be divided into two steps inspiration and expiration. Inspiration or inhalation is the taking in of air into the lungs. Expiration or exhalation is the forcing of air out of the lungs. Ventilation is brought about by alternate contraction and expansion of the thoracic cavity. This is brought about by two set of muscles the external and internal, intercostal muscles and the diaphragm, which is a large sheet of muscle. When breathing in (inspiration) the muscles of the diaphragm contract, this pulls the diaphragm downward making it flat. At the same time the external intercostal muscles contract. This pulls the rib cage upwards and outwards. Together these movements increase the volume of the thorax. As a result, the pressure insite it falls and the air rushes in to fill and expand the lungs. Fig 10.9 Ventilation When breathing out (expiration) the muscles of the diaphragm relax, so that it springs back up into its dome shape. At the same time the external intercostal muscles relax and the rib cage of drop down again into its normal position. This decreases the volume of the thorax and increases the pressure inside so the air is squeezed out. The internal intercostal muscles are used when breathe more forcefully like coughing.

Ventilation is an important step of respiration because it continuously supplies oxygen for cellular respiration without which life is not possible. It also performs the vital function of removal of toxic carbon dioxide from the body.


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10.6.2 Composition of inhaled and exhaled air:

Oxygen

Inhaled 21%

Exhaled 16%

Carbon dioxide

0.04%

4%

Nitrogen Water vapours

78% Variable

78% High

Temperature

Variable

Warm

Reason of difference Oxygen is absorbed into the blood across gaseous exchange surface. Carbon dioxide brought by the blood is released across the gaseous exchange surface. Nitrogen gas is not used by the cells. Water evaporates and is lost as air breathed out. Usually Air is warmed which it es through the respiratory age.

As the exhaled air contains 16% of oxygen mouth to mouth breathing is possible in case of emergency.

10.6.3 Effect of exercise on the rate and depth of breathing and its relation to energy requirements: Some times, as in case of a continuous exercise, muscle cells may need a lot of oxygen very quickly, for which we breathe deeper and faster to inhale more oxygen. Our heart beat and blood circulation become faster. Eventually a limit is reached. The heart and lungs cannot supply oxygen to the muscles any faster. But more energy is still needed for the movement of the muscles. This energy debt is met by anaerobic respiration. Some glucose is broken down, even in the absence of oxygen, producing lactic acid. This does not release much energy, but a little extra might make all the difference. When we stop the exercise we have quite a lot lactic acid in our muscles and blood. The deposition of lactic acid makes the muscles fatigue and one feels tired. This lactic acid must be broken down by combining it with oxygen. The amount of oxygen needed to remove this lactic acid from the muscles is called the oxygen debt. For this purpose we breathe deeper and deeper to pay the oxygen debt. 10.7 DISORDERS OF RESPIRATORY SYSTEM ASSOCIATED WITH CIGARETTE SOMOKING

AND

HEALTH

RISH

According to World Health Organization (WHO) smoking could become the world’s biggest killer by the year 2020, causing more deaths than any other diseases. 10.7.1 Smoking Smoking affects the lungs. Heavy smoking can also damage the heart and blood vessels. Non-smokers are also affected if they spend much time in a room with people who are smoking. Cigarette smoke contains three main ingredients. These are nicotine, tar and carbon mono-oxide. Each of these has its own effects on the body. Nicotine is addictive. Once the body gets used to it, it is very hard to do without it. It increases the heart beat and blood pressure and causes heart diseases. Tar increases the chances of getting lung cancer. Where as carbon mono-oxide is poisonous. 10.7.2 Bronchitis


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It is the inflammation of the bronchial tubes, which may be caused by smoking or by bacterial infection. When a person smokes, tiny particles in the smoke get caught on the lining of the trachea and bronchial tubes. Extra mucus is produced and the cilia stop beating. The mucus collects in the bronchial tubes and this gives rise to “smokers cough”. If the tubes become infected, the person may get chronic bronchitis; chronic means long lasting, so the disease persists. 10.7.3 Tuberculosis It is another disease of the lungs caused by bacteria (Mycobacterium tuberculosis) which destroy the lung tissues. It can be diagnosed by chest X-ray and sputum test. At one time T.B was one of the most common causes of death, but modern medicine has now nearly cured it. 10.7.4 Lung Cancer Today lung cancer has taken over from T.B as the major killer. In lung cancer a growth develops in the wall of the bronchial tubes. This blocks them, so breathing becomes more and more difficult. The lung cancer can be detected by chest Xray. If a growth is visible, it is removed by surgery or may be destroyed by radiation therapy. Other common respiratory diseases are: Laryngitis _____ inflammation of the larynx Pneumonia _____ severe inflammation of the lungs caused by a type of bacteria (Pneumococcus).


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           


SUMMARY Respiration is a process that liberates chemical energy stored in the organic molecules. Some of the energy is stored in the form of ATPs, the rest escapes as heat energy. Cellular respiration takes place within the cells. Aerobic respiration takes place in the presence of free oxygen, releasing maximum energy. Anaerobic respiration occurs without oxygen producing less energy. Respiration is a catabolic exothermic reaction where as photosynthesis is an anabolic endothermic reaction. Fermentation is the anaerobic respiration, resulting in the formation of alcohol or lactic acid. Most of the gaseous exchange in plants takes place through leaves either directly or through stomata. Animals have a variety of ways for gaseous exchange some respire through body surface, some have respiratory organs like gills, tracheal tubes, book lings and lungs. Human breathing system consists of a pair of lungs and the associated tubes. The gaseous exchange takes place within the alveoli. Bronchitis may be caused by smoking, tuberculosis is caused by a bacterium. Lung cancer is an abnormal growth of the lung tissue.

1. Fill in the blanks with appropriate : i. The process which liberates chemical energy stored in food is called________. ii. Energy can only be used by organisms in the form of________ iii. When an ATP molecule is hydrolyzed to ADP________ kj of energy is released. iv. Respiration completes in two phases breathing and________ v. Accumulation of________ causes the muscle to fatigue. vi. Respiratory reactions take place in ________. vii. Gaseous exchange in plant chiefly occurs through________. viii. ________ are the respiratory organs in fishes. ________ are the bunches of grape like air sacs where exchange of ix. gases takes place in lungs. x. The amount of oxygen required to remove the accumulated lactic acid from the muscle is called________. 2. Write whether the statements are true or false i. One can survive without oxygen for weeks. ii. Respiration is the process of oxidation of food for release of energy iii. ATPs are the currency of energy of an organism. iv. Respiration and combustion are somewhat similar reactions. v. Stomata are the places of exchange of gases in plants. vi. Tracheae are the respiratory organs in insects. vii. Movement of air in and out of the body is also called ventilation. viii. Photosynthesis is catabolic reaction. ix. ATPs are synthesized in mitochondria. x. Fermentation is a process of anaerobic respiration. 3.

Encircle the appropriate answer: i) Respiration take place in a) Parenchymatous cells b) In leaves cells c) All cells d) In root cells ii) What is the importance of respiration in plants?


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4.

5.

6.

7.


a) It liberates energy b) It provides oxygen to plants c) It liberates carbon dioxide d)All of the above iii) The end-products of respiration in plants are b) Starch and O2 a) CO2, H2O and energy c) Sugar and O2 d) H2O and energy iv) Alcohol is produced during the process of a) Aerobic respiration b) Anaerobic respiration c) Photosynthesis d) None of them v) In animals the product of anaerobic respiration is a) Uric acid b) Uracil c) Lactic acid d) Pyruvic acid. vi) Plants gain weight due to a) Respiration b) Photosynthesis c) Transpiration d) None of the above vii) The respiratory organs of insects are a) Flame cells b) Malpighian tubules c) Tracheae d) Lungs viii) The intake of O2 and release of CO2 by blood ing through the capillaries of the alveoli are brought by a) Diffusion b) Osmosis c) Active transport d) None of them ix) Tuberculosis is causes by a) Virus b) Bacteria c) Worm d) None of the above x) Cigarette smoke contains a) Nicotine b) Tar c) CO d) All of them Write detailed answers of the following questions: i) Describe the breathing system of man. ii) Describe the respiratory organs of insects and molluscs. iii) How does gaseous exchange take place in plants? iv) What are the disorders of respiratory system? How is health risk associated with cigarette smoking? v) What is cellular respiration? Explain its types with the help of chemical equation. vi) Prove that respiration is a catabolic process and photosynthesis is an anabolic process. vii) Explain inspiration and expiration. Compare the composition of inhaled and exhaled air. Write short answers of the following questions: i) What are ADP and ATP? What is their importance? ii) What is the importance of anaerobic respiration? iii) Why do people have to breathe deeply after vigorous exercise? iv) Trace the path of exchange from air to alveoli of man. v) What are the characteristics of a respiratory surface? Define the following : i) Cellular respiration ii) ATP and ADP iii) Fermentation iv) Photosynthesis v) Bronchitis Distinguish between the following: i) Aerobic and anaerobic respiration ii) Respiration and Photosynthesis iii) Breathing and Cellular respiration


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iv) v)

Combustion and respiration Respiration and expiration


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