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the process of sexual maturation is gradual, and takes place while general body growth is still going on. Therefore, some degree of sexual maturation does not necessarily mean that the body or the mind is ready for sexual acts. Further, it is not fit for having and bringing up children. How do we decide if the body or the mind is ready for this major responsibility? All of us are under many different kinds of pressures about these issues. There can be pressure from our friends for participating in many activities, whether we really want or not. There can be pressure from families to get married and start having children. There can be pressure from government and voluntary organisations to avoid having children. In these situations, making right choices is important. In the lesson why do we fall ill, we learnt that the diseases can be transmitted from person to person in a variety of ways. Since the sexual act is a very intimate connection of bodies, it is not surprising that many diseases can be sexually transmitted. These include bacterial infections such as Gonorrhoea and syphilis, and viral infections such as AIDS (Acquired Immuno Deficiency Syndrome). • What is the virus which causes AIDS? These diseases spread by unsafe sexual contacts, using infected devices, infected blood transfusion, from an infected mother to child. Free distribution by A.P. Government fig-31: Red ribbon 1st December AIDS Day 137 It is very sad to say Andhra Pradesh has the highest number of HIV positive patients in the country. According to official statistics, the state had 24 lakh HIV positive patients in the country during 2011-12. Maharashtra, Karnataka are followed by Andhra Pradesh. Officials said that one in every 300 adults is suffering from HIV elsewhere. The prevalence of HIV is 1.07 percent among males and 0.73 among female in the state, which again is higher than other states. Its prevalence among adults (15-49 years) 0.90 percent, pregnant women 1.22 percent in Andhra Pradesh. Illiteracy, poor health, unemployment, migration, non-traditional sex practise, unethical contacts and trafficking are some of the factors contributing to the spread of HIV in the state, according to experts. The government established Anti Retroviral Therapy (ART centres) to supply medicine to HIV patients. Medical and health, family health departments AIDS control projects implementing various programmes like ASHA (Accredited Social Health Activist), Red Ribbon Express, etc., to create awareness in society on the risks and symptoms of AIDS. • Invite local health

worker to your school and discuss about HIV and its impact on society. Social discrimination against AIDS patients is also a social evil. Can you support this? Why? If we follow the simple life styles as cited below one could avoid • many sexually transmitted diseases. • Avoid sex with unknown partners/multiple partners • Even though contraceptives are available it is better follow ethical and • healthy life practices. In case of doubt, go to a qualified doctor for early detection and get complete treatment if diagnosed with disease. Birth control methods The sexual act always has potential to lead to pregnancy. Pregnancy will make major demands on the body and the mind of the woman, and if she is not ready for it, her health will be adversely affected. Therefore, many ways have been devised to avoid pregnancy. The prevention of pregnancy in women by preventing fertilisation is called contraception. Any device or chemical (drug) which prevents pregnancy in woman is called a contraceptive. The birth control methods can be of various types and can be used by any of the partners as preferable. Physical devices such as condoms and diaphragm (cap) are used. This 138 X Class Reproduction - The generating system prevents reaching of sperms to ova for fertilisation. This device not only prevents fertilisation but also transmitting some sexually transmitted diseases (STD) like gonorrhoea, syphilis and AIDS. No other method of contraception provides protection against sexually transmitted diseases. Chemicals in the forms of pills are induced either orally or inserting into female reproductive organ vagina. It contains hormones which stop the ovaries from releasing ovum into the oviducts. Now a days pills for males are also available. These pills kill the sperms and hence are called spermicides. blood supply vasdeferens epididymis testis small incision copper - T vasectomy - cut ends of vas deferens are sealed fig-32: Birth control methods cauterised tied and cut tubectomy - cut ends of follopian tubes are sealed banded The use of intra-uterine device called copper-T, loop etc. are also very effective in preventing pregnancy. If a woman uses a copper-T as a method of contraception for avoiding unwanted pregnancies, they cannot protect her from acquiring sexually transmitted diseases. Surgical methods of birth control are available for males as well as females. In males a small portion of vas deferens (sperm ducts) is removed by surgical operation and both ends are tied properly. This method is called vasectomy. In

females a small portion of oviducts (fallopian tube) is removed by surgical operation and the cut ends are tied. This prevents the ovum from entering into the oviducts. This method is called tubectomy. Fighting against social ills Teenage motherhood We have studied how complicated the process of reproduction is. Child birth is even more complicated. Understanding it and getting prepared for it needs maturity of the mind and body. Thus a girl only after 18 years of age can be said to be prepared for the same. Most of the times this age is also dangerous to the girl. According to the department of family welafare 21% of teenage mothers die during delivery. So girls below 18 years of age should not be marry. Stop female foeticide Who knows today’s girl child may become a great scientist, a famous doctor, a top class engineer, a dedicated administrative officer, a world Free distribution by A.P. Government 139 renowned economist, a wonderful teacher of an unmatched world leader of tomorrow. Stop female foeticide! Save the girl child. Due to reckless female foeticide the male female child sex ratio is declining at an alarming rate in some sections of our society. Our government has already enacted laws to ban on determination of sex of foetuses. In spite of laws it’s a social responsibility of us to prevent female foeticide. • Why doctors are prohibited to do sex determination through altrasound scanning for pregnent women? We know that if health is lost, everything is lost. It’s our responsibility to be healthy and to make others realise the importance of health. Sound body is to sound mind. To be an ideal citizen of India we should have knowledge of reproductive health not only to control high population growth but to create a healthy society. Key words Progeny, cyst, fragmentation, regeneration, vegetative propagation, artificial propagation, parthenogenesis, cutting, layering, grafting, stock, scion, desirable characters, tissue culture, amniotic fluid, placenta, umbilical cord, mitosis, meiosis, chromatid, chromosome, foeticide, HIV-AIDS, vasectomy, tubectomy. What we have learnt • Reproduction is necessary for perpetuation and continuation of life. • Reproduction is of two types keeping in view of fusion of gametes- Sexual and Asexual. • • • In sexual reproduction only half of each parent’s chromosomes are passed to the next

generation. Fission, budding, fragmentation, regeneration, spore formation are the ways of asexual reproduction. Several plants may be grown from vegetative parts like stems, roots, leaves etc and is called vegetative propagation. • Vegetative propagation may be natural or man made. It has got some economic importance. • • • In grafting we can acquire desirable characters of plants. Tissue culture is a modern technique of growing plants. It helps to grow more plants in less time and place. Sexual reproduction in higher animals is through specialised organs, distinctively male and female reproductive systems. • Cells divide for growth of the individual to repair and replace the worn out cells and also for the formation of gametes. 140 X Class Reproduction - The generating system • Cell division is of two types-a) Mitosis-or somatic cell division B) meiosis-or reproductive cell division. The cell of the body may either be somatic cells that constitute the general body of the organism or germ cells that take part in formation of gametes. • • G-1, G-2, S and M are the stages in a cell cyclic which occur in a manner. The longest phase is the synthesis phase in cell cycle where duplication of genetic material takes place. • • At the end of mitosis two daughter cells are formed with the number of chromosomes same as that of their parents. It runs through Prophase, Anaphase Metaphase and Telophase. • Division of cytoplasm is called Cytokinesis. During meiosis the parent cell divides twice and four daughter cells are formed. • • Reproductive health is important to possess sound mind in a sound body. • One should be aware of the facts related to transmission of sexually transmitted diseases. There is no cure for AIDS. Prevention is the only way to avoid it. • • Now a days various methods of contraception are available to control child birth. • It is our responsibility to build a healthy society. • Determination of sex before birth is illegal. • Stop female foeticide. Improve your learning 1. Why do fish and frog produce a huge number of eggs each year?(AS1) 2. Give examples and explain what is meant by external fertilisation?(AS1) 3. Write differences between.(AS1) a) asexual reproduction - sexual reproduction b) stamen-carple 4. Explain the process of fertilisation in plants.(AS1) 5. What are the

different modes of asexual reproduction? Cite them with examples.(AS1) 6. In what ways does sexual reproduction differs from asexual one? State at least three reasons.(AS1) 7. How are sperm cells adapted for their function?(AS1) 8. The menstrual cycle prepares the uterus for a fertilised egg. How long is an average menstrual cycle from start to finish?(AS1) 9. When the foetus is growing inside the uterus it needs nutrients. What provides these nutrients?(AS1) 10. What does the mother’s blood take away from the baby and into the placenta?(AS1) 11. What is the job of the amniotic sac?(AS1) 12. What are the advantages of sexual reproduction?(AS1) 13. How does reproduction help in providing stability to population of species?(AS1) 14. Write the differences between mitosis and meiosis.(AS1) 15. What happens to the wall of the uterus during menstruation?(AS2) 16. “All unicellular organisms undergo only mitotic cell division during favourable conditions”- Do you support this statement? Why?(AS2) Free distribution by A.P. Government 141 17. Vicky’s father wants to grow a single plant having two desirable characters colourful flowers and big fruits What method will you suggest him and why?(AS3) 18. Uproot an onion plant and take a thin section of its root tip. Stain it and observe under microscope. Draw as you see and identify the stages of the cell division.(AS3) 19. Visit a nearby village and collect information how farmers grow sugarcane, flowering plants like chrysanthamum, primerose and vegetables like stem tubers, plump gourd (dondakaya) etc. Make a report and submit in class.(AS4) 20. Collect information from school library or using internet what vegetative methods are followed in your district as well as in your state to propagate various plants of economic importance. Represent it in a graph.(AS4) 21. Make a flow chart to show the cell cycle and explain cell division describing different stages of mitosis.(AS4) 22. Draw neat labelled diagrams of male and female reproductive system of plant.(AS4) 23. Observe the following part of a flowering plant prepare a note.(AS5) 24. Prepare a flow chart to explain the process of sexual reproduction in

plants.(AS5) 25. Draw a neatly labled diagram to explain plant fertilisation. Write few points on pollen grain.(AS5) 26. What would be the consequences if there is no meiosis in organisms that reproduce sexually?(AS6) Q.No.23 27. How will you appreciate cell division that helps in perpetuation of life? (AS6) stigma style ovary ovule gametophyte cells embryo sac 28. What precautions will you take to keep away from various sexually transmitted diseases?(AS7) Choose the correct answer 1. The part of the female reproductive system that produces the eggs? ( a) Ovary b) Epididymis c) Cervix d) Fallopian tube 2. The term that we use to describe a sperm cell fusing with an egg cell? a) Fragmentation b) Fermentation c) Fertilisation d) Fusion 3. Which part of the male reproductive system produces (human) the sperm cells? a) Vasdiference b) Epididymis c) Bladder d) Scrotum ( ( ) ) ) 4. How does the sperm break through the egg cell membrane? Choose the option you think is right. a) Tears a hole in the membrane b) Dissolves the membrane with chemicals ( c) Bites through the membrane with teeth d) Squeezes through gaps in the membrane 5. Why are egg cells larger than sperm cells? Choose the option you think is right. ( ) ) a) Egg cells have more cells in them b) Have food store to help growth after fertilisation c) Have thicker cell membranes d) Have larger nuclei 142 X Class Reproduction - The generating system 6. Which of these things will affect the way a foetus grows? Choose the option you think is right. ( ) a) Chemicals in cigarette smoke b) Alcohol c) Drugs d) All of the above 7. Which of the following is the correct sequence of steps in the human life cycle? Choose the right option. ( ) a) Babyhood, childhood, adolescence, adulthood b) Childhood, babyhood, adulthood, adolescence c) Adolescence, babyhood, adulthood, childhood d) None of these Annexure Dr. Potu Narasimha Rao, a renowned scholar and an eminent cytologist came from a poor family in Muppalla village of Guntur district. He completed his graduation in Agriculture and did his MS at IARI, New Delhi. Later,

be involved in the breakdown of food in the stomach? • If any of those processes fail to function, what affect would it have on our body? Every process is dependent on other to keep the body in good condition. To understand this concept we analyze how digestive system is coordinated with other systems as an example. We shall study the digestive system from feeling hungry to utilization of food, illustrating the inter connected processes going on in our body. 144 X Class Coordination in life processess Feeling Hungry • How do we know that we need food? Activity-1 Let us observe the following table. Identify and tick those options that you think makes you feel hungry. Table-1 Smell of food Taste of food Sight of food Being tired and exhausted Need of food Thought of food • What stimulates hunger? • What would be the result of stimulation of hunger? • Which system do you think would send the signals to make us realize that we are hungry? Well, a major cause for feeling hungry lies in the physiology of blood circulation. Levels of different substances are generally maintained in the blood mainly by our digestive system. One of the major substances is glucose. When its levels in the blood fall, we get hunger pangs in stomach. This again involves production of a series of proteins, some of which are hormones like Ghrelin. Secretion of the hormone “Ghrelin” in the stomach when it goes empty. Ghrelin is secreted from certain cells in the wall of the stomach. Hunger contractions (hunger pangs) start to occur in the stomach due to hunger generating signals that reach the brain from the stomach due to the secretion of this hormone. It is believed that the Diencephalon in fore brain and vagus nerve (10th cranial nerve) plays an important role in carrying these signals to the brain. Hunger pangs continue up to 30- 45 minutes. Increase in ghrelin levels results in sensation of hunger and motivation to consume food. • What kinds of controls are exercised during sensation of hunger? Are they hormonal or neural or both? • Can you suggest any 4 systems involved in the process of generating hunger sensation? When you feel your stomach is full and there is no need of food any Free distribution by A.P. Government 145 more, another hormone leptin is secreted that suppresses hunger. Usually we take food at a particular time. Every day we usually start feeling hungry at that time. You may have experienced this in your school during lunch hour. Outcome of sensation of hunger

We find that different organ systems are involved in the digestive process. Let us find more about how the organ systems are involved. Feeling hungry leads us to consume food. Sometimes you may have often experienced that stale food is out rightly rejected even before intake. • What plays a major role to identify stale food? • If you are having a tasty dish do you think the smell of it increases your appetite? Taste and smell are closely related Taste and smell are intimately entwined. This close relationship is most apparent in how we perceive the flavors of food. Anyone with severe cough and cold can not make out the difference in tastes of certain food items. Actually, what is really being affected is the flavor of the food, or the combination of taste and smell. That’s because only the taste, not the food odors, are being detected. Taste itself is focused on distinguishing chemicals that have a sweet, salty, sour, bitter, or umami taste (umami is Japanese for ‘savory’). However, interactions between the senses of taste and smell enhance our perceptions of the foods we eat. The following activity helps us to observe how are taste affected by the sense of smell. Activity-2 Chewing, cumin (fenugreek), sounf (fennel seeds), potato and apple First close your nose with your fingers. Pop in some zeera in your mouth and chew it for some time. After that, chew some sounf. Could you recognize the taste? How long has it taken to know the taste? After some time wash your mouth and repeat the activity by chewing a piece of an apple followed by a potato(remember to close your nose). • What are your observations? To conclude, if you want to taste the food material, the food should dissolve in saliva. On the other hand, we can taste the food that is in the form of liquid only. We know that different types of taste buds are present 146 X Class Coordination in life processess on the tongue. You have also learnt about different types of papillae (taste buds) on the tongue for different tastes in ninth class. Let us recall them. Only after the dissolved food enters into the cup like taste buds, the sense of taste is carried to the brain for analysis. Then only we will know the taste of the food material. • Could you know the taste of both or did it taste villate apillae foliate papillae fungiform papillae fig-1: Pap

illae on tongue the same? Why? When we smell, the air borne substances get dissolved in the watery film of nasal mucus. The chemoreceptors in nose are other wise called olfactory receptors which trigger signals in the form of nerve impulses to the brain where smell is detected. Similarly as we take food into our mouth the taste buds sends signals to the brain. Picking up the slight differences in smell the food tastes are identified in our brain. • What happens when we put a food material in our mouth? • Name the parts in the mouth that help us to taste food. Let’s find out more about the role of these parts. Activity-3 Take a pinch of asafoetida powder or garlic and rub it on hand kerchief or tissue paper. Close your eyes and smell it. Then try to identify taste of different types of food materials with the help of your friend. • Does garlic have a stronger scent than apple? How do you think the stronger scent affect your sensation of taste? • How many food materials you have identified correctly? • Write a few lines on relation between smell and taste? • Have you ever felt that a particular food is tasty just by looking at it? Sometimes mouth starts watering just by hearing the name like tamarind / lime / mango etc., Now let us summarize the result of the activities with the help of your answers. In general, we prefer the food material, which is attractive to our eyes, and flavor to nose, then we taste it. Therefore, when we eat, without our knowledge, we use our sight, nose and tongue for selecting food for ingestion. Free distribution by A.P. Government 147 Russian scientist Pavlov has conducted experiments and found that even the thought of food will water your mouth (conditioned reflexes). You have discussed about Pavlov experiment in the chapter animal behavior in class 9th. • Are there any other sensation that affect taste? • What happens to your taste sensation while sipping hot milk or tea? You may also find something more tastey when they are hot. While some others are relished cool. • What do you think could be the range of temperature for us to relish food items? Taste is something connected to the tongue and the palate Let us do a simple activity to see the role of different parts of the mouth in helping us to taste. Activity-4 Sugar crystals over the tongue Place some sugar crystals on your tongue keep your mouth opened and see that your tongue doesn’t touch

the palate. Record the time from the moment you placed the crystals on your tongue till you got the taste by using stop watch. palate tongue Now repeat the test by placing the sugar crystals on the tongue and pressing it against the palate. Record the time from placing sugar crystals to getting the taste.Or put a drop of sugar solution on your tongue using a dropper. fig-2: Tongue and palate • Can we taste on dry tongue? • Which way helped you taste faster? Why? Based on the above activity we know that taste can be identified easily when the tongue is pressed against the palate. As we know the tongue is sensory in function and contains taste buds. These taste buds are tiny papillae with an opening on top. Within them there are several taste sensitive cells. Any food substance when placed on the tongue gets dissolved in the saliva secreted by salivary glands in the mouth. When the tongue is pressed against the palate the food substance is pressed against the opening of the taste bud letting it to reach the taste cells and triggering taste signals. Finally the taste is recognized in the brain. 148 X Class Coordination in life processess Taste Nose Mouth Tongue Brain Olfactory receptors Salivary glands Taste buds • What do you think would happen if the salivary glands do not function in our mouth? • Suppose your taste buds were affected what would happen to your interest in having food? Mouth - the munching machine Would you be able to comfortably munch your food if you had lost some of your teeth? Activity-5 To show break down of food by using the model of chalkpiece kept in vinegar Break a piece of chalk into two halves. Crush one half to tiny pieces leaving the other as it is. Take two small mineral water bottles (1/2 ltr bottle) cut them into two equal halves and discard the upper portion. Now we have two beakers from the lower cut portion. Fill them half with vinegar and add the crushed chalk to one beaker and the other uncrushed half chalk to the other. Obseve them after half an hour or so. • Which one dissolved faster the crushed chalk or the whole one? The above experiment tells us the need of mechanical crushing of food. Hence the food in the mouth has to be broken down into tiny pieces to increase the surface area for action of substances that aid in digestion. • How does this process of mechanical crushing go on in the mouth? • Which parts in the mouth are involved in this? • What are the

systems involved in this process? You know that teeth helps in chewing food material. Let us know about different types of teeth in our mouth and how they helps in digestive process. Free distribution by A.P. Government 149 Activity-6 } molars (3) } } premolars (2) canine (1) inscissors (2) fig-3: Dentition Observe the model or chart of jaw, how are the teeth arranged? Are all the teeth similar in shape and size? Is there any relation between shape and function of the teeth? Dental formula explains the arrangement of teeth. On the basis of the figure try to guess what could be the the function of molars? You had studied in earlier classes inscissors have sharp edges, canines have sharp and pointed edges while molars and premolars have blunt and nearly flat surface. • What do you think could be the function of inscissors? • Which set of teeth help in grinding food? • Which set helps in tearing food? • What is your dental formula? Now fill up the following table with proper information based on the figure given here. Table-2 Type of teath Number Shape Function The circular muscles of the mouth enable the food to be pushed into the oral cavity and to be moved around. As the food cannot be swallowed directly the teeth grind, chew and shred it. This process is called mastication. For this purpose the surface muscles of the jaw help in biting and chewing actions, and move the jaw up, down, forward and backward during food mastication. You may have observed your lower jaw moving up and down as you chew food. The teeth help in cutting and grinding while tongue movements evenly spread out the food and help in mixing it with saliva. The muscles of the mouth enable the food to be pushed in the oral cavity and to be moved around. The fifth cranial nerve has been found to control the movement of muscles in the jaw. 150 X Class Coordination in life processess • Does the level of saliva secretion change due to presence of food in the mouth? • Can the process of chewing go on in the absence of saliva? • Does the saliva have any other roles to play? Let us find out the role of saliva. Activity-7 Action of saliva on flour (ata) Take a test tube half filled with water and add a pinch of flour to it. Shake the test tube well till the flour gets mixed. Take a few drops of this in a watch glass and test for the presence of starch by

putting a drop of diluted tincture iodine in it. A blue black color confirms the presence of starch. Now again dissolve a pinch of flour into half filled water in a test tube. Now divide the mixture into two equal halves by transferring it to another test tube. Note that both the test tubes have the same amount of solution. Add a teaspoon of saliva to one of the test tube and mark it. Do not add anything in the other test tube. After some time (45minutes) add a drop of dilute Tincture Iodine solution to test tubes containing the solution. • Do you observe any change in the solutions? Why does the change occur? • Do you think the same process goes on in the mouth when food is taken? Under the action of autonomous nervous system saliva is secreted by three pairs of the salivary glands to moisten the food to make chewing and swallowing easier. As a result of chewing, food forms into a slurry mass called ‘bolus’ that is transported into the oesophagus by the action of swallowing with the help of the tongue. The enzyme salivary amylase in the saliva breaks down the large starch molecule into smaller subunits usually into sugars. The mechanism for swallowing is also under nervous coordination and its control center is somewhere in the brain stem (medulla oblongata and others). During mastication food size becomes convenient to swallow. • What is the use of such an increase in surface area of food? • What about the nature of medium for salivary amylase to act on food component? • If we swallow food material directly without mastication what will happen? • Do you think the pH of our mouth changes? Free distribution by A.P. Government 151 Activity-8 Testing pH of mouth at intervals of one hour. Ask your chemistry teacher to give you a strip of pH paper with a colour chart. You can do this in your school by taking a small piece of the pH paper and touching it to your tongue. Match the colour with the colour chart and note the pH first. See to it that you are able to take some readings after having your food at lunch break. Compare your readings with that of your friend. Take at least 4 readings. You have to prepare your own table to record your observations. • What is the usual range of pH of your mouth? Acidic or basic? • Did you observe any change in pH after eating? What may have caused the change? • In what kind of

pH do you think salivary amylase acts well? • Does the type of food have any role to play on the pH of our mouth? Test with different types of food as you eat them and check just after you have swallowed them. Do not hurry to complete the table. Take your own time. (pH beyond 7 is alkaline, pH- below 7 is acidic, pH 7 is neutral). Based on the above tests we know that the saliva secreted causes the medium to change to alkaline as it aids in action of enzyme, salivary amylase. fig-4: pH Do you know? • Why do we salivate during a nap of daytime? You have heard about Nocturnal animals, which are active during nights, but we are active during daytime and take rest at night. All the systems of our body are active in function during the time of our activity. Hence, man is a diurnal animal. Our digestive system is also active and ready to receive the food for digestion. If we sleep during daytime saliva oozes out of our mouth and wets the pillows. This will not happen during night time. We secrete 1-1.5 liters of saliva per day. • What are the different systems that contribute to the proper functioning of digestion in the mouth? • After the digestive process in the mouth where does the food move to? 152 X Class Coordination in life processess Travel of food through oesophagus The oesophagus receives the food pushed by the swallowing action of the mouth. • What are the systems that come into play for swallowing food? The following schematic representation shows some functional and stuctural attributes of oeasophagus. Observe it and answer the following questions. Walls secrete mucus slimmy substance Long tube upper end connects to pharynx lower end connects to the stomach passes food to stomach by wave like movement of walls (peristalsis) Oesophagus muscular and elastic walls carry on wave like movement by contraction and relaxation • What does the schematic diagram tell us about the oesophagus? • What kind of the tube is oesophagus? • How does mucus help in passage of food? Activity-9 Making a model of oesophagus to observe how bolus moves forward Take a piece of waste cycle tube and insert one or two potatoes into it. Lubricate the inner side of the tube with oil. In the same way smear oil over the potatoes. Insert oil coated potatoes

in the tube. Now try to push the potatoes by squeezing the tube. • How do you squeeze the tube to make the potatoes pass through? • Do you think that the muscles in the wall of the oesophagus have to do something like this? • How did oil heip you in pushing the pototoes through the pipe? Peristaltic movement in oesophagus Look at the fig-6, which shows wave like movement of wall of oesophagus and observe the position of the food bolus. fig-5: Potato in cycle tube Free distribution by A.P. Government 153 • How did the position of the bolus change? • What is the similarity of movement of food illustrated in the diagram and the activity performed by you? epiglottis up oesophageal sphincter contracted relaxed muscles contracted muscles stomach bolus sphincter relaxed The walls of the food pipe secrete a slippery substance called mucus. Mucus lubricates and protects the oesophageal walls from damage. This helps the food bolus to slide down easily just as the oiled potatoes that move in the tube. Besides this, the saliva in the bolus also aids in easy movement of food, which moves into the stomach. The wall of the oesophagus is made up of two kinds of smooth muscles. The inner layer consists of circular muscles and the outer layer of longitudinal muscles. Contraction of the circular muscles results in narrowing of the oesophagus just behind the bolus. So the food is squeezed downwards. Contraction of the longitudinal muscles infront of the bolus widen the tube, this results in shortening of that particular part of the oesophagus. Contraction and relaxation of these muscles bring in a wave like motion that propels the food bolus into the stomach by the action called as “peristalsis” (you have studied about this in the chapter on nutrition). This is involuntary and under the control of autonomous nervous system. fig-6: Peristalic movement of bolus • What makes the movement of the food bolus in the oesophagus easy? Think why people are advised not to swallow food without chewing properly or do not eat in hurry. Stomach the mixer and digester • Why do you think the stomach is structured like a bag rather than a tube like oesophagus? • What sets such processes into action? When the food is in the oral cavity, the nerves in

the cheek and tongue are stimulated. These carry messages in the form of nerve impulses-to the brain. These messages are transmitted from the brain, to the wall of the stomach, and stimulate the gastric glands to produce gastric juice. The walls of stomach secrete juice containing hydrochloric acid (HCl) Most of us may have experienced belching and the burning sensation after it. What do you think may have caused the burning sensation? These secretions are stimulated by the nervous system. The contraction of the 154 X Class Coordination in life processess stomach muscles squeeze and mix the food with the acids and juices of the stomach. These digestive juices turns the food into a smooth porridge like consistency called chyme. Some large protein molecules are also broken down here. • What stimulates stomach muscle into action? • What causes the stomach to churn and mix the food? As the process of digestion in the stomach nears completion, the contractions of the stomach decrease. What would be the reason? Which substance present in blood regulates contraction of stomach? This prompts the muscles, called as pyloric sphincter at the opening of the stomach and the first part of the small intestine or duodenum, to relax. This opens the pathway into duodenum releasing the partially digested food (chyme) in small quantities into the duodenum. • Why should only a small quantity of food be passed from stomach to duodenum? pyloric valve closed pyloric valve closed pyloric valve slightly opened. Propulsion: Peristaltic waves move food from one part to the other. Grinding: The most vigorous peristalsis and mixing action occur close to the pylorus. Retropulsion: Small amounts of chyme is pushed into the duodenum, simultaneously forcing most of it back into the stomach. fig-7: Peristalic movement in stomach Peristalsis involves the contraction of the muscle behind the food and the relaxation of the muscle in front of the food giving rise to a thrust that pushes the food forward through the digestive canal. A wave of contraction followed by relaxation in muscles helps in forward movement of food. • What is involved in bringing about peristalsis? • What is the direction of peristalsis (which end of the gut does it begin)? • What happens if the direction of peristalsis is reversed? Have you observed a ruminating cow/ buffalo under a tree or somewhere else? Carefully observe its neck and

throat. Do you see something moving from its throat to mouth? After that, the cow or buffalo starts chewing. It is the bolus moving from a part near the stomach of the animal to its mouth. It is reverse peristalsis. Though it is a common process Free distribution by A.P. Government 155 in ruminants such as the cow, buffalo etc. that have an extra pouch in the stomach to store quickly swallowed food, in human beings it is mainly a protective mechanism to expell unwanted substances from the food canal. We observe that digestion of food starts from the mouth. While the food passes through the gut the food settles for some time for digestion at certain locations. So food does not move uniformly through the digestive system. Let us observe the time period. Table-3 Percentage 50% Total 100% Emptying of stomach Emptying of small intestine 2.5 to 3 hours 4 to 5 hours 2.5 hours 30 to 40 hours (Transit through colon) (These are only averages. The movement of materials varies among individuals and time after different meals.) Our stomach is not like a bag with specific volume. It is like a pouch which is elastic in nature. the size of the stomach increases based on the food that we intake. Digestive juices are produced depending on the quantity of food material. If the stomach would produce same amount of digestive juices irrespective of the food quantity the walls of stomach would be destroyed. We also know that stomach secretes strong acids during digestion. The HCl secreted by the walls of the stomach is strong enough to digest the hard bones as well..Then how is the stomach protected from the secretions of its own acids. To understand this we will perform the following experiment. Lab Activity Take two similar green leaves. Grease one leaf with petroleum jelly leave the other free. Add 1 or 2 drops of some weak acid on both the leaves.Observe them after half an hour or so and write your observation in your note book. • Which leaf was affected by the acid? • What kind of change did you observe in the leaves? • What saved the other leaf from the effect of acid? Mucus secreted by some cells present in the walls of the stomach 156 X Class Coordination in life processess form a thin lining on the walls of the stomach. This counters the action of acid. The function of petroleum jelly can be compared to that of mucus lining the stomach walls. Hence the stomach is protected from damage being caused by the secretion of

its own acids. Travel of food from the stomach to the intestine Now food is a soup like mixture when it leaves the stomach and enters the small intestine. When the food enters the intestine the acidic nature of the chyme initiates the production of hormones like secretin and cholecystokinin which stimulate pancreas, liver and walls of small intestine to secrete pancreatic juice, bile juice and succus entericus. The absorption of nutrients by villi in the small intestine is a very selective process. The walls of the intestine allows only tiny nutrient particles to pass through. • Why do you think small intestine is long and coiled? • What process is involved in this process of absorption? Activity-10 Paper tube and folded papers Take 1020cm size chart paper fold the chart paper and join both ends with gum to make a tube. Now take 2020cm chart paper and make a tube as mentioned the same above try to insert the big tube in small one. Can you? It is not possible. Now take another 2020cm chart paper fold the paper as many folds as possible. Now join both ends to make a folded paper tube. Try to insert folded tube in first tube. Can you? How is it possible? • Compare the area of the folded papers with that of the roll. Do you find any increase in the area?If so try to find out the reasons? The inner surface of the small intestine contains thousands of finger like projections called villi. These villi increase the surface area so that the food retained in the folds can remain longer thereby enhancing absorption. • What systems do you think are working together here? fig-8: Paper tube epithelium network of blood mucus mucus gland lacteal (part of • Do you think those systems work together in the whole length of the digestive canal? Why/ Why not? fig-9: Schematic diagram of a villus Free distribution by A.P. Government 157 The digestive tract is unique among internal organs because it is exposed to a large variety of physiochemical stimuli from the external world in the form of ingested food. As a consequence, the intestine has developed a rich store of co ordinated movements of its muscular apparatus along with neural apparatus to ensure the appropriate mixing and propulsion of contents during digestion, absorption, and excretion. The neural apparatus of our digestive tract comprises of such a vast and complicated network of neurons that it has been nicknamed by scientists as the second brain! Research in this area is currently investigating how the second brain medi

ates the body’s immune response; after all, at least 70 percent of our immune system is aimed at the gut to expel and kill foreign invaders. Scientists are also working to find out how trillions of bacteria in the gut ‘communicate’ with the cells of gut nervous system. A deeper understanding of this mass of neural tissue, filled with important neurotransmitters, is revealing that it does much more than merely handle digestion or inflict the occasional nervous pang of hunger. The little brain in our inner yards, in connection with the big one in our skull, partly determines our mental state and plays key roles in certain diseases throughout the body. • Often you may have experienced that if you have tension for some reason you start having loose motions. What does this show us? Although its influence is far-reaching, the second brain is not the seat of any conscious thoughts or decision-making. Technically known as the enteric nervous system, the second brain consists of sheaths of neurons embedded in the walls of the long tube of our gut, or alimentary canal, which measures about nine meters end to end from the oesophagus to the anus. The second brain contains some 100 million neurons, more than in either the spinal cord or the peripheral nervous system. This multitude of neurons in the enteric nervous system enables us to “feel” the inner world of our gut and its contents. Stimulating and coordinating the breaking down of food, absorbing nutrients, and expelling of waste requires chemical processing, mechanical mixing and rhythmic muscle contractions that move everything down the line. Thus equipped with its own reflexes and senses, the second brain can control several gut functions often independently of the brain. Several scientists also believe that the system is a way too complicated to have evolved only to make sure things move through and out of our gut smoothly. 158 X Class Coordination in life processess Expulsion of wastes Explusion of wastes via blood through the kidneys, skin etc., are mainly salts, water and urea. Undigested food matter is expelled in the form of stool. • What moves out of the gut? • Two major pathways of waste expulsion are shown above. Which of the two do you think happens exclusively through the gut? Imagine you made a roll by wrapping a hand full of left over tea leaves in a tissue paper. Later you press the roll gently and open it. What did you observe? You find the tissue paper had absorbed the water from the tea leaves. Similarly when the unwanted waste material

(stools / faeces) reach the large intestine. The peristaltic waves move the stool into the rectum. The left side of the colon acts like a storage tank of faeces. Water gets reabsorbed and the remaining wastes usually hard mass gets stored in the last part (Rectum) of the large intestine. This smelly yellowish faecal mass usually called as stool is later expelled out of the body through the anus. • What controls the exit of stools from the body? • Do you think the control is voluntary? Why / why not? There are two muscular layers helping the exit of stool. One that is under involuntary control and the other is under voluntary control. These muscular structures help in opening and closing of the aperture of the canal which are called as anal sphincter. rectum sphincter anus fig-10: Anal spincter • Did we have a sphincter in any other part of the digestive cannal? Where was it? Suppose a person has consumed more fluids than what the body actually need. How do think the extra fluid will be removed from the body? We have so far seen how several systems work together to bring about the process of digestion. Where does this process draw energy from to run smoothly? Free distribution by A.P. Government 159 • What is the fate of the digested substances that move into blood from the intestine? If energy has to be obtained from food it has to be oxidised. For this purpose respiration has to go on. During inhalation oxygen moves across the walls of the alveoli and enters the blood. From here it enters the red blood cells and gets distributed throughout the cells of our body. At the same time carbon dioxide from the blood moves into the alveoli of the lungs and breathed out during exhalation. Nutrients in the cells get oxidized and energy is released. • Where is the energy stored? • Which system do you think will remove the excess salts from our body? • What would be the path of salt removal from gut to the out side of our body? During respiration we breathe continually by inhaling and exhaling air. This is an involuntary process controlled by the medulla oblongata of the autonomous nerves system (ANS). During respiration the movement of inter costal muscles/diaphragm moves the ribs cage inflating and deflating the lungs. Air containing more of oxygen enters the blood stream through lungs. If the oxygen has

to reach the tissues it has to be circulated through blood. How does this process go on? Hence the process of digestion which is a complex process that involves many organs and organ systems. Though digestion occurs in the food canal, co-ordination of respiration and blood circulation is necessary otherwise oxidation of food and transport of substances which is vital for energy releasing process will not take place. This may lead to the shut down of systems interdependent on each other. Key words Ghrelin, Leptin, Gustatory, Chemoreceptors, Papillae, Food bolus, Peristalsis, Chyme, Pyloric Sphincter, Villi, Medulla oblongata, Brain stem. What we have learnt • The food taken by us it has to be broken down into constituent substances for proper digestion, assimilation and energy releasing processes. 160 X Class Coordination in life processess • The human digestive system involves both the muscular and nervous systems. • A special nervous system that exists in the gut consist of nearly 100 billion nerves that coordinates the muscular activity,blood flow,digestion and absorption of nutrients and other activities of the food canal (gastro intestinal tract). • The hormone Ghrelin secreted in the stomach is responsible for hunger generating sensations. Another hormone leptin that gets secreted suppresses hunger. • Taste can be identified easily only when the tongue is pressed against the palate. • Taste and smell are closely related. The chemoreceptors receptors present in the nose and and the tongue trigger signals in the form of nerve impulses to the brain where the smell and taste is detected. • The saliva secreted maintains an alkaline medium that aids in digestion of starch. Our mouth secretes acid as well,this gives protection to our mouth from harmful bacteria etc., Under the action of autonomous nervous system Saliva released by the salivary glands moistens the food to make chewing and swallowing easier. • The muscular and sensory organ in the oral cavity is the tongue which is not only gustatory in function but also performs different functions including, shifting and mixing the food in the oral cavity and swallowing. • The mechanism for swallowing is coordinated by the swallowing centre in the brain stem. • Contraction and relaxation of the muscles in the gut brings in a wave like motion that propels the food forward and is called peristalsis. This is a muscular wave that travels the entire length of the food canal. This is involuntary and under the control of autonomous nervous system as well as gut nervous

system. • The muscular contractions of the stomach churns the food into a semiliquid substance known as chyme. Entry of chyme into the duodenum is regulated by a muscle called as the pyloric sphincter. • The strong acid (HCl) renders the pH in stomach acidic causing the protein digesting enzymes to swing into function. Juices secreted in the stomach breaks down the food into a smooth mixture called chyme. • • The mucus lining of the stomach protects it from damage by its own acids. • The coordination among the processes of digestion, respiration and circulation is necessary for utilization and oxidation of food and transport of the nutrients. Muscular and nervous control helps to carry out the processes in a regulated manner. Improve your learning 1. What do you meanby hungerpangs?(AS1) 2. What are the organ systems involved in digestion of food which we eat?(AS1) 3. Rafi said smell also increase our appetite can you support this statement. how?(AS1) 4. Write a note on peristalsis and sphincter function in stomach.(AS1) 5. Observe the given part of the digestive system. What is it? What is it’s role during digestion?(AS1) 6. Give reasons.(AS1) a) If we press tongue against the palate we can recognise taste easily. b) We can’t identify taste when food is very hot. Free distribution by A.P. Government Q.No: 5 161 c) If glucose level falls in blood we feel hungry. d) Small intestine is similar to a coiled pipe. e) Urination increases when we take lot of fluids f) The process of digestion goes on in a person whose central nervous system has been largerly affected 7. Write difference between the following.(AS1) a) bolus - chyme c) mastication - rumination b) small intestine - large intestine d) propulsion - retropulsion 8. How can you say that mouth is a munching machine?(AS1) 9. What is mastication? Explain the role of different sets of teeth in this process.(AS1) 10. During the journey of food from mouth to stomach through oesophagus. How muscular system coordinate in this process?(AS1) 11. Is there any reason for the intestine to be coiled with many folds.In what way it is helpful during

the process of digestion?(AS1) 12. What is the function of peristalsis in these parts?(AS1) b) stomach a) oesophagus 13. How can you justify the enteric nervous system as the second brain of the gut?(AS1) 14. Rajesh feels hungry upon seeing food.Sheela says no to food as she is not hungry.What makes c) small intestine d) large intestine Rajesh hungry and what suppresses Sheelas hunger?(AS1) 15. How are taste and smell related?(AS1) 16. List out the sphincter muscles of the food canal you have observed and give a brief description?(AS1) 17. What experiment should you perform to understand action of saliva on flour? Explain it’s procedure and opparatus that you followed.(AS3) 18. What happens if salivary ducts are closed?(AS2) 19. If size and shape of small intestine is like oesophagus what will happen?(AS2) 20. Prepare a questionnaire to understand nervous coordination in digestion process.(AS2) 21. Suggest a simple experiment to prove the role of palate in recognizing taste.(AS3) 22. Collect information related to feeling hunger from your school library and prepare a note on it.(AS4) 23. Draw the block diagram showing sensation of taste from food material to brain.(AS5) 24. Draw a neatly labled diagram showing a peristaltic movement in oesophagus. Explain the importance of mucus on the walls of food pipe.(AS5) 25. Draw a schematic diagram of villus in small intestine. Explain how digestive system coordinate with circulatory system.(AS5) 26. The mere smell or sight of food stimulates hunger.Describe the process through a neat diagram?(AS5) 27. With the help of a diagram show the movement of food from mouth to the stomach.What muscles and nerves are involved in the movement of food and what is this action called as?(AS5) 28. Prepare a cartoon on Pavlov’s experiment with a suitable caption.(AS6) 29. How do you appreciate stomach as a churning machine.How does this coordination go on?(AS6) 30. There is a great variety in diversified life processes, express your feelings in the form a poem.(AS7) 31. Suggest any two important habitual actions to your friend while eating food, keeping

in view of this chapter.(AS7) 162 X Class Coordination in life processess Fill in the blanks 1. 3:2:1:2 is the ratio of our dentition. Here 1 represents ____________ 2. Large protein molecule are broken down in _________ of digestive track. 3. __________ is the strong acid which is secreated during digestion. 4. Olfactory receptors present in ___________ trigger signals to brain. 5. pH of saliva is _________ in nature. 6. Fill in the blanks with suitable words given below. Fluctuation s of hormone (i)_____________ levels results in sensation of hunger and motivation of consuming food. When you feel your stomach is full and there is no need of food any more. Another hormone (ii)_____________ that gets secreted suppresses hunger. When we take food into the mouth it has to be chewed thoroughly. For this purpose the (iii)_____________ muscles help in chewing actions, while the (iv)_____________ muscles of the jaw moves the jaw up,down,forward and backward during food mastication. The (v)_____________ nerve controls the muscles of the jaw.. Under the action of (vi)_____________ nervous system Saliva is released by the salivary glands moistens the food to make chewing and swallowing easier. The salivary (vii)_____________ in the saliva breaks down the starch into sugars. As a result of chewing the food is transported into the oesophagus by the action of swallowing which is coordinated by the swallowing centre in the (viii)_____________ and the (ix)_____________. The tongue which is gustatory recognizes the taste and (x)_____________ nerve plays an important role in sensation of taste. Choose the right ones. 1) leptin, grehlin gastrin secretin. 2) ghrelin leptin secretin gastrin. 3) deep muscles,surface muscles,circular muscles, striated muscles. 4) surface muscles, deep muscles, neck muscles, long muscle. 5) fifth cranial nerve,second cranial nerve,fifth facial nerve, spinal nerve. 6) central nervous system, peripheral nervous system autonomous nervous system. 7) lipase, sucrase, galactase,amylase. 8) medulla oblongata, cerebrum, 8th spinal nerve,cranial nerve.7th cranial nerve. 9) Pons varoli, brain stem,med

fast from breakfast time till 4’0 Clock and then introduced food into the stomach through the flap. The sensation of hunger subsided. Though it was fortuitous experiments in medicine connected to digestion raised many questions. • What is the cause of hunger? • How does the brain know the happenings of the stomach? • What causes the gastric juices to secrete? • How and what makes the food to be mixed with the digestive juices? • Does the process of digestion occur independently or involves other systems like nervous and muscular as well? Free distribution by A.P. Government 165 Chapter 8 Heredity - From parent to progeny When we observe our world and its myriad forms of life, we are struck by two seemingly opposite observations, the fantastic variety of life and the similarity between them. As we shall see, we would need to understand these two characteristics of life in order to understand how life evolves. When we say that something evolves, we mean not only that it changes, but that there is also some component of direction in that change. But, how does evolution take place? Does it occur in a slow and steady manner or in quick jumps? Is it just about change and producing something new and different? In the chapter on reproduction we had studied that reproductive processes usually give rise to individuals that have some new characters in spite of the similarity that they share with their parents. Often such new characters give rise to observable changes in life forms. • How are new characters produced? • Are they inherited? • Do they have any role in the process of evolution? In this chapter we shall try to explore several such questions. New characters and variations Think of your own family, what similarities do you share with your father and your mother? Draw a table to represent the similarities of some characters like colour of eye(cornea), colour of hair, shape of nose, shape of face, type of ear lobe(attached or free), inner thumb markings etc. Write your characters and that of your parents in two separate other columns. 166 X Class Heredity - From parent to progeny • How many similar characteristics do you find among you and your • parents? Is there any character in you that is neither like your father nor like your mother? • Where do you think you got such a character from? Let us do an activity to find out more about this. Activity-1 Compare your traits with the traits of your parents and grand parents by drawing a table as given below in your notebook. Characters In me In my Mother/

Father In my grandma / grandpa Table-1 • Is there any character in you similar to that of your mother as well as your grandma? Is there any character in you similar only to that of your grandma? • • How do you think these characters may have been inherited by you • from grandma? Is there any character that is not present in grandma but present in your mother and you? • Think where from your mother got that character? Activity-2 Observe some of your friends and note their characters in the following table. Fill in yours as well. Table-2 Name of your friend Colour of skin Ear lobes Free/ attached Marking on inner side of thumb Length of fore head Colour of eyes (Cornea) Any other features Free distribution by A.P. Government 167 • Compare your characters to that of any one of your friend. How many characters did you find were similar among you and your friend? • Do you share more similar characters with your parents or with your friends? • Do you think that your differences from parents are same as differ- ences from friends? Why /why not? fig-1: Variations in organs Differences in characters within very closely related groups of organisms are referred to as variations. Often a new character in a group may lead to variations that are also inherited. • Is variation all about apparent differences? Is it about some subtle differences as well that we most often overlook? (Remember looking for two similar neem /doob grass plants in the chapter on diversity and classification in class IX) Activity-3 Observe seeds in a pea or bean pod. You may observe several parts to arrive at a generalisation. • Can you find two similar seeds there? • What makes them vary? (Hint: You know that seeds are formed from ovules) • Why variations are important? How are variations useful for an organism or a population? Over centuries variations and their role in nature have been studied by naturalists. During early 19th century, a lot of work was done by several scientists. Some of these studies will help us to understand how variations occur and are transferred from one generation to the next. We shall study a detailed account of experimental evidences provided by Mendel in the early 19th century who is known as ‘father of genetics’. In 1857 Gregor Johann Mendel started working on the problem of how variations were passed from one generation to the other. Mendel did 168 X Class Heredity - From parent to progeny fig-

2: Gregor Johann Mendel not do his experimental work either in a University or in a Laboratory. As he was a monk in a monastery he simply did his experiments in the monastery garden. He worked for over seven years after which he presented the conclusions from his experimental data in the form of a detailed research paper. Mendel made many careful observations of plants and found that pea plants would be most suitable to carry on futher experimentation. Then he planned and designed the experiments to find out the answers to questions that came to his mind. He had worked on nearly 10,000 pea plants of 34 different varieties. Observing pea plants carefully, Mendel noted that they differ from one another in many ways. For example plants were tall or dwarf, seed shape round or wrinckled, seed cover (cotyledon) colour yellow or green. Thus, Mendel had chosen 7 pairs of contrasting characters for his study as shown in the table-2. 1. The difference in the form of the ripe seeds. These are either round or deeply wrinkled. 2. The difference in the color of the seed albumen (endosperm). The albumen of the ripe seeds is either pale yellow, bright yellow and orange coloured, or it possesses a more or less intense green tint. This difference of colour is easily seen in the seeds as their coats are transparent. 3. The difference in the colour of the seed coat. This is either white, with the character of white flowers are constantly correlated, or it is grey, grey-brown, leather-brown, with or without violet spotting. 4. The difference in the form of the ripe pods. These are either simply inflated, not constricted in places, or they are deeply constricted between the seeds and more or less wrinkled. 5. The difference in the colour of the unripe pods. They are either light to dark green, or vividly yellow. 6. The difference in the position of the flowers. They are either axial, that is, distributed along the main stem, or they are terminal, that is, bunched at the tip of the stem. 7. The difference in the length of the stem. The length of the stem is varied in some forms. In experiments with this character, in order to discriminate with certainty, the long axis of 6 to 7 feet. was always crossed with the short one of 3/4 to 11/2 feet. (Popularly called the tall and dwarf varieties.) Free distribution by A

.P. Government 169 Table-3: The results of Mendel’s F1 crosses for seven characters in pea plants Character Dominant Trait Recessive Trait F2 Generation Dominant: Recessive Ratio Purple White Flower colour 705:224 3.15:1 Flower position Axial Terminal Yellow Green 651:207 3.14:1 Seed colour 6022:2001 3.01:1 Round Wrinkled Seed shape 5474:1850 2.96:1 Inflated Constricted Pod shape 882:299 2.95:1 Green Yellow Pod colour 428:152 2.82:1 Tall Dwarf Stem length 787:277 2.84:1 170 X Class Heredity - From parent to progeny Mendel hypothesized that characters were carried as traits and an organism always carried a pair of factors for a character. He also hypothesized that distinguishing traits of the same character were present in the population of an organism. He assumed that the traits shown by the pea plants must be in the seeds that produced them. The seeds must have obtained these traits from the parent plants. How do parent plants pass on their traits to the seeds? Will the seeds from tall plants always produce new tall plants? Mendel carried out several experiments to find out answers to such type of questions. Examples of experiments performed by Mendel The following section shows number of experiments performed, number of fertilizations carried out and the number of plants involved in the study. 1. 1st experiment 60 fertilizations on 15 plants. 2. 2nd experiment 58 fertilizations on 10 plants. 3. 3rd experiment 35 fertilizations on 10 plants. 4. 4th experiment 40 fertilizations on 10 plants. 5. 5th experiment 23 fertilizations on 5 plants. 6. 6th experiment 34 fertilizations on 10 plants. 7. 7th experiment 37 fertilizations on 10 plants. • Why Mendel had choosen garden pea as material for his experiments? Because it has following advantages. 1.Well defind characters, 2.Bisexual flowers, 3.Predominently self fertilization, 4.Early hybridization Mendel selected such kinds of plants that expresses a selected character over several generations. Such plants according to him were pure breed for that character. Mendel did the experiment with two pure breeds of peas for seed colour contrasting characters yellow and green, and they are represented as yellow with ‘Y’ and green with ‘y’. He started cross fertilizing pure

breeds having contrasting characters. Mendel started with two pure breeds of peas with different properties. We here take as an example a characteristic colour of the pea seeds yellow and green. Do you know? Pea is an annual plant, with a life cycle of one year. It is a cool season crop grown in many parts of the world. Peas were present in Afghanistan in 2000 BC, in Harappa, Pakistan, and in northwest India in 2250– 1750 BC. In the second half of the 2nd millennium BC, this pulse crop appeared in the Gangetic basin and southern India. Pea contains vitamin ‘A, C, E, K & B’ and minerals like Ca, Fe, Mg, Mn, P, S & Zn. Free distribution by A.P. Government 171 Cross pollinating a pure breed of yellow and green gave First Filial (F1) generation (Mendel called it as first filial or progeny of first generation parents. Filial means progeny.) All pea seeds were Yellow. These pea plants on self pollination gave Second Filial (F2) generation [About 75% yellow (seeds) peas and about 25% green (seeds) peas.] Third Filial (F3) generation (Mendel self pollinated these pea plants too, and found out that 1 2 3 1 2 3 1. A set of peas (about 25%) gave only yellow seed giving pea plants. 2. Rest of the yellow seed giving pea plants gave about 75% yellow and about 25% green seed giving pea plants. 3. The set of green peas gave only green seed giving pea plants. Mendel made some assumptions by which he could explain his observations. Assumption 1: Every pea plant has two ‘factors’ which are responsible for producing a particular character or trait. The determining agent responsible for each trait is called a factor. Mendel carefully choose the plants which did not produce a mixed result (pure). In our example of yellow and green peas, a pure breed (parental stage) will have both the ‘factors’ of the same type. A pure breed (parental) yellow seed giving pea will have both the ‘factors’ of the same type. Let us denote them by ‘Y’. A pure breed (parental) green seed giving pea will have both the ‘factors’ of the same type

. Let us denote them by ‘y’. 172 X Class Heredity - From parent to progeny Assumption-2 : During reproduction one ‘factor’ from each parent is taken to form a new pair in the progeny. Assumption-3 : One of these will always dominate the other if mixed together. The trait expressed in F1 generation was called dominant. While the other which did not express was called recessive. Assume that ‘Y’ (the one causing yellow colour) is a dominating ‘factor’. That means if ‘Y’ and ‘y’ come together ‘Y’ will dominate. Then the pea seeds will be always yellow in colour. From assumption-2, the breed after cross pollination will have one factor from pure breed yellow (Y) and one from the pure breed green (y). That is, all the peas will have the paired factor ‘Yy’ and by assumption-3 all the peas will be Yellow as ‘Y’ factor is dominant. Parental generation - Cross pollination y y Y Yy Yy Y Yy Yy Yy............... (yellow) Yy............... (Yellow) Yy............... (yellow) Yy............... (Yellow) All the pea plants are yellow (F1-Generation). The trait expressed in F1 is dominent, unexpressed is recessive. This is the law of dominenance. Self pollination in F1-Generation On self pollinating these peas (ones with Yy factor), the new breed have any combinations of ‘Y’ and ‘y’. y y Yy YY yY yy Y y It can be YY, Yy, yY or yy. All of them are in equal ratio. So in this heap we will get approximately equal number of YY, Yy, yY and yy peas. But any pea that has a Y factor will be yellow. Any pea that has both yy will be green. Since all combinations are equally likely: 1. YY will be approximately 25% and is yellow. 2. yY will be approximately 25% and is yellow, Yy will be approximately 25 % and is yellow 3. yy will be approximately 25% and is green. Some seeds appear yellow in colour in F1 generation. When these Free distribution by A.P. Government 173 seeds

were sown some of the plants produced green coloured seeds. So we can’t determine internal character based on external visible character. Phenotype Thus in F1 generation we can clearly observe that 75 percent are yellow seed producing pea plants and 25 percent are green ones. This is known as ‘Phenotype’(externally visible characters) and this ratio is called ‘phenotypic ratio’ is 3:1. Genotype Genetically, in 75 percent yellow seed producing pea plants only 25 percent pea plants produce yellow seeds that are pure breeds (YY) and are ‘homozygous’ that is to have the same factors for representing a character. Remaining 50 percent yellow seed producing pea plants are (Yy) heterozygous. The remaining 25 percent green seed producing pea plants are pure (yy) homozygous type. The constitution of pea plants as shown by the representative letters Y and y to show the probable nature of factors is known as genotype. This ratio is known as genotypic ratio is 1:2:1 On self-pollinating these peas of F2 generation we get, Y Y YYY YY Y YY YY 1 Y y YYY Yy y yY yy 2 y y y yy yy y yy yy 3 1. The YY peas will on self pollination give only yellow (YY) peas. This was explained with the experimental result that this set gave 100% yellow peas. 2. The Yy or yY peas on self pollination give about 75% yellow peas and about 25% green peas. This situation is same as step 2 ratio 3:1. 3. The green peas that contain yy factors will give only green peas. In nature there are many factors responsible for different properties. • Can we test our hypothesis with more than one factor? How can this be applied to Mendel’s experiment? This can be done 174 X Class Heredity - From parent to progeny together when two pairs of contrasting characters are taken into consideration. 1. Colour of peas-yellow and green symbolically indicated as ‘Y’, ‘y’. 2. Shape of peas-Round and wrinkled symbolically indicated as ‘R’, ‘r’. The plants with yellow and round seeds (pure) were crossed with those having green and wrinkled seeds (pure). All pea seeds that were yellow and

round skin. Each pea will have factors ‘YyRr’. Since Yellow colour (Y factor) and round skin (R factor) are dominant traits. All the pea seeds will be round and yellow (F1 generation). He got in F2 generation some seeds were round and yellow (YyRr or YYRR), some seeds were round and green (yyRR or yyRr), some seeds were wrinkled and yellow (Yyrr or Yyrr), and some seeds were wrinkled and green (yyrr). YYRR yyrr On cross pollination YyRr Self pollination • What should be the percentage of each type? Mendel explained the process of inheritance of more than one pair of characters. This law is known as law of independent assortment. We will learn more about this in further classes, for the basic understanding refer in annexure. Mendel propounded that, among a pair of closely related ‘alleles’ or factors for a character, only one expresses itself in the first generation as one of the allele is dominant over the other. This is so evident that it came to be called as Mendels’ Law of Dominance. He also stated that, every individual possesses a pair of alleles (assuming only a pair is present) for any particular trait and that each parent passes a randomly selected copy (allele) of only one of these to an offspring. The offspring then receives its own pair of alleles for that trait one each from both parents. This is what Mendel called ‘segregation’ and it is the Law of Segregation. Free distribution by A.P. Government 175 ’ B ‘ G A B Traits that may be passed on from one generation to the next are called as heritable traits. We have studied some of them for the pea plant, in the experiments conducted by Mendel. Activity- Let us do the following activity to understand the Mendelian principles of Heredity. BAG ‘A’ 1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16 Materials required : a) 3 cm length and 1cm breadth chart pieces- 16 b) 2 cm length and 1cm breadth chart pieces- 16 c) Red buttons - 16 d) White buttons - 16 e) Chart, scale, sketch pen, pencil, 2 bags. Method: Prepare a chart with 44 boxes along with number and Symbol as shown in the figure

Game 1: Monohybrid cross (starting with hybrid parents) To start with take 1,2 or 3,4. In case you start 1,2 pick all the 16 long and short pieces and prepare such pairs in each of which you have a long and short piece. Take 8 pairs each of long and short strips and put them in two separate bags. Now each bag contains 16 strips (8 long and 8 short).One bag say ‘A’ represents male and the bag ‘B’ represents female. Now randomly pick one strip each from bag A and B and put them together in the 1 on the chart. Keep picking out the strips and arrange them in the same manner till your bags are empty. Sametime your boxes in the chart are filled with pairs of strips. You might have got the following combinations, two long strips, one long and one short strip, two short strips. • What is the number of long strip pairs? • What is the number of one long and one short pairs? • What is the number of short strips pairs? • What is the percentage of each type? also find their ratios? • What can you conclude from this game? You may play this game by taking buttons instead. Compare your second game results with that of first game. What do you understand. Try to play another game mentioned in annexure then discuss with your classmates. 176 X Class Heredity - From parent to progeny Parent to progeny A person resembles his grandfather, a girl seems to be a photocopy of her aunt, generally we hear such comments. These similarities are the result of inherited traits transmitted from parent to progeny. Let us do the following activity to understand inherited traits in human beings. According to Mendel traits like the colour of seed, seed coat, length of stem etc. were heritable traits from parental generation. Transmission or passing of characters or traits from parent to offsprings is called ‘Heredity’. The process in which Traits are passed from one generation to another generation is called ‘Inheritance’. How do traits get expressed? Mendel hypothesised that each character or trait is expressed due to a pair of factors or ‘alleles’ (contrasting expressions of the same trait), as he named them. Now we know that these are known as ‘genes’. Gene is a segment of a nucleic acid called ‘DNA’ which is present in the nucleus of every cell

. It controls the expression of a trait or character. In vireses RNA can also be controlling the expression of a character. Do you know? In 1953 the detailed structure of DNA was finally worked out at Cambridge by Francis Crick and James Watson. They discovered that DNA molecule looks rather like a spiral stair case, having a shape known as a double helix. The framework of stair case consists of alternate sugar and phosphate groups and the steps which join the framework together are the pairs of chemical compounds called bases. They are adenine, guanine, thymine and cytosine. Watson and Crick were awarded Nobel prize jointly with Franklin and Maurice Wilkins. Traits are determined by the chemical nature of DNA and a slight change in it leads to variations. Colour of the hair, the skin etc. are examples of trait. Slight inheritable changes in the chemical structure of DNA may lead to change in the characteristic or trait of offspring of an organism, which leads to ‘Variations’. Watson DNA fig-3: Crick Free distribution by A.P. Government 177 Sex determination in human beings mother’s sex chromosomes father’s sex chromosomes female child Father Mother male child Parents 44+XY 44+XX 22 +X Gyno Sperm 22 +Y Andro Sperm 22+X 22+X Gamates Eggs Offsping Baby girl Baby boy Baby girl Baby boy (44+XX) (44+XY) (44+XX) (44+XY) fig-4: We inherited our traits from our parents. Let us see how sex is determined in human beings. Each human cell contains 23 pairs (46) of chromosomes. Out of 23 pairs 22 pairs of chromosomes are autosomes. Chromosomes whose number and morphology do not differ between males and females of a species are called autosomes. The remaining pair is called allosomes or sex chromosomes. These are two types, one is ‘X’ and the other is ‘Y’. These two chromosomes determine the sex of an individual. Females have two ‘X’ chromosomes in their cells (XX). Males have one ‘X’ and one ‘Y’ chromosomes in their cells (XY). All the gametes (ova) produced by a woman have only X chromosomes. The gametes (sperm) produced by a man are of two types one with X chromosome and other Y chromosome. If the sperm carries Y chromosome and fertilizes the ov

um (X chromosome). Then the baby will have XY condition. So the baby will be a boy. • What will happen if the sperm containing Y chromosomes fertilizes the ovum? • Who decides the sex of the baby – mother or father? • Is the sex also a character or trait? Does it follow Mendels’ law of dominance? • Were all your traits similar to that of your parents? Do you know? Discovery of the sex chromosomes Walter Setton and Thomas Hunt Morgan in the year 1910 studied on a small fruit fly (Drosophila melanogaster) at Columbia University. The discovery of sex linked traits in Drosophila indicated that genes are on chromosomes. They worked out the details of inheritance in Drosophila. 178 X Class Heredity - From parent to progeny Evolution Variations develop during reproduction in organisms. Sexual reproduction and errors in DNA copying leads to variations in offsprings in a population. Let us try to study the consequences of variations in the population of an insect in an environment. Activity-3 Variations in beetle population Observe the below diagram showing variation in beetle population and it its impact. fig-5: Variation in population Let us consider a group of twelve beetles. They live in bushes on green leaves. Their population will grow by sexual reproduction. So they were able to generate variations in population. Let us assume crows eat these red beetles. If the crows eat more Red beetles their population slowly reduced. Let us think of different situations. Situation-1: In this situation a colour variation arises during reproduction. So that there appears one beetle that is green in colour instead of red. fig-6: Red and green beetles Free distribution by A.P. Government 179 More over this green coloured beetle passes it’s colour to it’s off spring (Progeny). So that all its progeny are green. Crows cannot see the green coloured beetles on green leaves of the bushes and therefore crows cannot eat them. But crows can see the red beetles and eat them. As a result there are more and more green beetles than red ones which decrease in their number. The variation of colour in beetle ‘green’ gave a survival advantage to ‘green beetles’ than red beetles. In other words it was naturally selected. We can see that the ‘natural selection’ was exerted by the crows. The more crows there are, the more red beetles would be eaten and the more number of green

beetles in the population would be. Thus the natural selection is directing evolution in the beetle population. It results in adaptation in the beetle population to fit in their environment better. Let us think of another situation. Situation-2: In this situation a colour variation occurs again in its progeny during reproduction, but now it results in ‘Blue’ colour beetles instead of ‘red’ colour beetle. This blue colour beetle can pass its colour to its progeny. So that all its progeny are blue. fig-7: Blue and red beetle Crows can see blue coloured beetles on the green leaves of the bushes and the red ones as well. And therefore crows can eat both red and blue coloured beetles. In this case there is no survival advantage for blue coloured beetles as we have seen in case of green coloured beetles. What happens initially in the population, there are a few blue beetles, but most are red. Imagine at this point an elephant comes by and stamps on the bushes where the beetles live. This kills most of the beetles. By chance the few beetles survived are mostly blue. Again the beetle population slowly increases. But in the beetle population most of them are in blue colour. Thus sometimes accidents may also result in changes in certain characters of the a population. Characters as we know are governed by genes. Thus there is change in the frequency of genes in small populations. This is known as “Genetic drift’, which provides diversity in the population. 180 X Class Heredity - From parent to progeny Let us think of another situation: Situation-3: fig-8: Poorly nourished beetles In this case beetles population is increasing, but suddenly bushes were affected by a plant disease in which leaf material were destroyed or in which leaves are affected by this beetles got less food material. So beetles are poorly nourished. So the weight of beetles decrease but no changes take place in their genetic material (DNA). After a few years the plant disease are eliminated. Bushes are healthy with plenty of leaves. • What do you think will be condition of the beetles? Acquired and Inherited Characters and Evolution We discussed the idea that the germ cells of sexually reproducing population are formed in specialised reproductive tissue. If the weight of the beetles is reduced because of starvation, that will not change the DNA of the germ cells. Therefore, low weight is not a trait that can be inherited by progeny of a starving beetle. Therefore even if some generations of beetles lose their weight because of starvation,

that is not an example of evolution, since the change is not inherited over generations. Change in non reproductive tissues cannot be passed on to the DNA of the germ cells. Therefore the experiences of an individual during its lifetime cannot be passed on to its progeny, and cannot direct evolution. Lamarckism In the olden days people believed that all the organisms on the earth had not undergone any change. Jean Baptist Lamarck was the first person to propose the theory of evolution. He thought that at some point of time in the history the size of giraffe was equal to that of deer. Due to shortage of food material on the ground and to reach the lower branches of trees giraffes started stretching their necks. Because of continuous stretching of neck, after several generations giraffes developed long necks. Such characters that are developed during the lifetime of an organism are called ‘acquired characters’. Lamarck proposed that these acquired fig-9: Jean Baptist Lamarck (1774-1829) Free distribution by A.P. Government 181 characters are passed on to its offsprings i.e. to next generation and proposed the theory of ‘Inheritance of acquired characters’. For example elongation of neck and forelimbs in giraffe. But Augustus Weismann, tested this theory by an experiment on rats. He removed tails of parental rats. He observed that their offspring’s are normal with tails. He has done it again and again for twenty two generations but still offsprings are normal with tails. He proved that the bodily changes are not inherited. So they won’t be passed to it’s offsprings. fig-10: Giraffee Darwinism Charles Darwin proposed ‘Natural selection’ the famous ‘theory of evolution’. Charles Darwin (1809-1882) was born in England. He voyaged for five years, just when he was 22 years old. In the world survey ship HMS Beagle. He visited a number of places including Galapagos Islands. He keenly observed the flora and fauna of these places. He gathered a lot of information and evidences. Darwin observed a small group of related birds which are exhibiting diversity in structure in the Galapagos islands. These birds are Finch birds. Observe the fig-12. How do the beaks help them. He was influenced by the book ‘Principles of geology’ written by Sir Charles Lyell. He suggested that geological changes

occured fig-11: Charles Darwin (1809 – 1882) Large ground finch (seeds) Cactus ground finch Vegetarian finch (buds) Wood pecker finch (insects) fig-12: Some Darwin finches in a uniform rate, Darwin did not agree to this idea. He felt that large changes occured due to accumulation of small changes. Darwin was also influenced by the famous ‘Malthus theory’. This was written in ‘An essay on the principles of population’. Malthus observed that population grows in geometrical progression (1, 2, 4, 8,......) where as food sources increases in arithmetic progression (1, 2, 3, 4, 5,.......). 182 X Class Heredity - From parent to progeny Based on these ideas Darwin proposed the theory of “Natural selection”, which means that the nature only selects or decides which organism should survive or perish in nature. This is the meaning of survival of the fittest. The organisms with useful traits will survive. If traits are not usefull to organisms then they are going to be perished or eliminated from its environment. Alfred Russel Wallace also independently concluded that natural selection contributed to origen of new species. For example we have seen in the case of red beetles which were seen and eaten by crows. So, the population of red beetles gradually got eliminated or perished from its environment. But at the same time the beetles which are green in colour which are present on the green leaves were not noticed by crows. So the green beetles survived in the environment and their population have gradually increased. This is nothing but “natural selection”. Think and discuss In a forest there are two types of deers, in which one type of deer can run very fast. Where as second type of deer can not run as fast as the first one. Lions, Tigers haunt deers for their food. Imagine which type of deers are going to survive in the forest and which type of deers population is going to be eliminated? And why? Variations which are useful to an individual are retained, while those which are not useful are lost. In a population when there is a struggle for the existence the ‘fittest’ will be survived. Nature favours only useful variations. Each species tend to produce large number of offsprings. They compete with each other for food, space, mating and other needs. In this struggle for

existence, only the fittest can survive. This is called ‘survival of the fittest’. Over a long period of time this leads to the formation of new species. You may observe in your surroundings some seedilings and some of the animal kids only survive. Discuss in your class based on those examples to understand survival of the fittest. Darwin’s theory of evolution in a nutshell 1. Any group of population of an organism developes variations and all members of group are not identical. 2. Variations are passed from parent to offspring through heredity. 3. The natural selection over abundance of offspring leads to a constant struggle for their survival in any population. Free distribution by A.P. Government 183 4. Individuals with variations that help them to survive and reproduce tend to live longer and have more offsprings than organisms with less useful features. 5. The offsprings of survivors inherit the useful variations, and the same process happens with every new generation until the variation becomes a common feature. 6. As the environment changes, the organism within the environment adapt and changes to the new living conditions. 7. Over a long period of time, each species of organism can accumulate so many changes that it becomes a new species, similar to but distinctly different from the original species. All species on the earth arise in this way. 8. Evolution is a slow and continuous process. There are some limitations and objections to the Darwin theory. Many new theories like synthetic theory, mutation theory are put forward. Do you know? Identical thoughts of Charles Darwin and Alfred Russel Wallace. When Charles Darwin was formulating the theory of evolution in his mind, he received a letter with an article sent by Alfred Russel Wallace about his studies in the Indonesian island. The article was about Natural selection. Darwin was surprised about same theory in his mind. Later in the same year Charles Darwin and Alfred Wallace jointly published an article in the ‘Journal of Linnaean Society’ about natural selection. It was only after this Darwin published his famous book, “The origin of Species” in 1859. However their thoughts gained criticism at that time because they did not explain how variations are inherited. After the discovery of mitosis and meiosis it was understood properly. Alfred Russel Wallace Speciation How new species are evolved? We have seen variations in a population of species, where the organism contain the traits that helped to adapt to the environment. These organisms are going to survive more efficiently. But in the same population the

organism which contains the non benificial traits may not be adapted in the environment. They are going to perish or eliminated slowly, like red and blue beetles in a population which we have discussed earlier in this chapter. These small changes within the species for example colour of 184 X Class Heredity - From parent to progeny beetles red and green is known as micro evolution. Now we are going to discuss how new species are formed. This is known as speciation, which is also known as Macroevolution. We have seen red and green beetles can mate each other and can have offsprings. But let us imagine that red and green beetles are separated by some cause (for example while eating beetles crows dropped some beetles accidently in the long distance far away places) for long years. There might be a lot of variations taken place in these years in the red and green beetle population. Now even though they may meet accidentally, they cannot mate and produce new offsprings. They can only mate in their population either red or green and can reproduce its off spring. Thus new species have been formed. Evidences of evolution How does the evolution of organisms taken place? Whatever scientists propose they require evidences or proofs. In the same way evolution of organisms requires evidences. Let us examine some of them. Homologous and analogous organs When we try to understand evolutionary relationships, we identify that some traits have common ancestors. These traits in different organisms would be similar because they are inherited from a common ancestor. You may be surprise to know that the internal structure of forelimb of a whale (swimmer) wing of a bat (flyer), leg of a cheetah (runner), claw of a mole (digger) and hand of a man (grasping). If we carefully observe the anatomy of all these animals, they show a common pattern in the arrangement of bones, even though their external form and functions are different. It indicates that all the vertebrates have evolved from a common ancestor and these organs are called homologous organs. This type of evolution is called divergent evolution. However, all similarities simply in organ shape are not necessarily to have a common ancestry. What would we think about the wings of birds and bats, for example (fig-). Birds and bats have wings, but squirrels and lizards do not. So birds and bats are more closely related to each other than squirrels or lizards. fig-13: Homologus organs Free distribution by A.P. Government 185 Before we

jump into this conclusion, let us look at the wings of birds and bats more closely. When we observe, we find that the wings of bats have skin folds (patagium) stretched between elongated fingers. But the wings of birds have a feathery covering all along the arm. The designs of the two wings, their structure and components are different. They look similar because they have a common use for flying, but their origin is not common. This gives the ‘analogous’ characteristics (Traits). As the above mentioned organs which are structurally different but functionally similar are known as ‘Analogous organs’. This type of evolution is called convergent evolution. Evidences from embryology Activity-5 Let us observe different stages of development of vertebrate embryos. Try to find out similarities and differences and discuss with your friends. Embryology is the study of the development of an organism from egg to adult stage. Tadpole of a frog resembles fish more than the frog. What does this indicates? Does it indicate that frogs have evolved from ancestors of fish? There are remarkable similarities in the embryos of different animals from fish to man. The resemblance is so close that at an early stage even an experienced embryologist would find difficulty to distinguish one embryo from the other. What does it indicate? Does it indicate that life history of every individual, exhibits the structural features of their ancestors? This strengthens the view of the existence of a common ancestor from which all these have evolved. Pig Calf Human Rabbit fish Salamander Tortoise Chick fig-14: Embryological evidences Evidences from fossils We know some species which existed million years ago, but we may not find them now. They might be extinct and some of them may be found in the form of fossils. For example we know Dinosaurs the biggest animal on land which were present long time ago but now they are extinct. The scientists got evidences of presence of Dinosaurs like animals in the form of fossils. 186 X Class Heredity - From parent to progeny What are fossils? Fossils are evidences of ancient life forms or ancient habitats which have been preserved by natural processes. Fossil evidence is typically preserved within the sediments deposited beneath water and land. They can be actual remains of once lived such as bones or seeds or even traces of past event such as dinosarus foot print or ripple marks on a pre-historic shore. Usually when organisms die, their bodies will be decomposed and lost. Sometimes the body or some

parts of the body do not decompose completely. For example if a dead insect get caught in mud, it will not decompose quickly and the mud will eventually harden and retain the impression of the body parts of insect. All such preserved traces of living organisms are called fossils. fig-15: Fossil Geologists can tell the age of a fossil. The study of fossil is called ‘Palaeontology’. Palaeontologists determine the age of fossil by using carbon dating method. The breakdown of radioactive isotopes of certain elements such as Carbon, Uranium and Potassium takes place at a known rate. So the age of rock or mineral containing isotopes can be calculated. • Collect information about carbon dating method and radioactive isotopes and discuss with your teacher or from library display your collections in your class. A rare and magnificient fossil of the dinosaurs, ketosaurs belonging to the lower Jurassic age going back to about 160 million years were collected from Yamanapalli in Adilabad district of Andhra Pradesh. This fossil has 14 metres length and 5 metres height. This fossil is preserved at BM Birla Science Centre in Hyderabad. fig-16: Dinosarus Do you know? See the picture of Archeopteryx. Does it resemble a bird? Or a reptile? Or both? The organisms which bear the characters of two different groups are called connecting links. Archeopteryx has some avian characters and some reptelian characters. Hence it is recognised as connecting link between aves and reptiles. Archeopteryx Free distribution by A.P. Government 187 Human evolution Human evolution is the evolutionary process leading up to the appearance of a modern human being. We the present human beings are also have an evolutionary history like plant and other animals. Early man like forms appeared about 7 lakhs 50 thousand years ago. The first sure fossil of our own species of man the Homosapiens, indicate that true man appeared on the earth 2 lakhs 50 thousand years ago. Evolution of man through ages: Homo habilus lived between 1.6 - 2.5 million years ago. Homo erectus lived between 1 - 1.8 million years ago. Homo sapiens neanderthalensis lived between 2,30,000 - 3,00,000 thousands years ago. Homo sapiens (present man) appeared about 40 thousand years ago. There is a great diversity in human forms and features across the planet. So that for a long time, people used to talk about human

‘races’. Skin colour used to be the commonest way of identifying the so called races. Some were called black, some white or brown. A major question debated for long time was, have these apparent groups evolved differently? Over recent years, the evidence has become very clear. The answer is that there is no biological basis to the notion of human races. All humans are a single species with a common ancestor. fig-17: Human evolution Not only that, regardless of where we have lived for the past few thousand years, we all come from Africa. The earliest members of the human species, Homo sapiens, can be traced there. Our genetic footprints can be traced back to our African roots. A couple of hundred thousand years ago, some of our ancestors left Africa while others stayed on, while the residents spread across Africa. The migrants slowly spread across the planet –from Africa to west Asia, Then to Central Asia, Eurasia, South Asia, East Asia. They travelled down the island of Indonesia and the Philippines to Australia, and they crossed the Bering land bridge to the Americas. They did not go in a single line, so were not travelling for the sake of travelling, obviously. They went forwards and backwards, with groups sometimes separating from each other, even moving in and out of Africa. Like all other species on planet, they had come into being as an accident of evolution, and were trying to live their lives the best they could. 188 X Class Heredity - From parent to progeny Human being - a moving museum During the course of evolution some organs remain in the organisms. You have studied about appendix in the digestive system. In human beings it has no role to play in the process of digestion. But in herbivores like rabbit appendix plays an important role. Such type of organs which are not useful in animal are called vestigial organs. • Think why did ancient human beings traveled from one place to other and how did they traveled? There are nearly 180 vestigial organs in human beings. For example pinna, hair on skin, mammary glands in human, etc. That’s why human being is said to be a moving museum of vestigial organs. Key words Variations, offsprings, traits, phenotype, genotype, heterozygous, homozygous, independent assortment, allele, heredity, autosomes, allosomes, natural selection, analogous organs, embryological evidences, Human evolution. What we have learnt • Variations

are quite apparent among closely related groups of organisms. • In about 1857 Gregor Johann Mendel started working on the problem of how variations were passed from one generation to other. • Mendel had choosen seven distinguishing traits: flower colour, position, seed colour, shape, pod • • • colour, pod shape, stem length. In monohybrid experiment F1 generation all pea seeds were yellow. In F2 generation about 75% seeds were yellow and about 25% seeds were green. This is called phenotype and the ratio is 3:1. In F2 generation out of 75%, 25% were pure yellow seeds 50% were yellow seeds but green as a recessive factor. Remaining 25% were pure green. This is called genotype and the ratio 1:2:1. • Every pea plant has two ‘factors’ which are responsible for producing a particular property or trait called allele. • The factors for each pair of characters assorts independently of the other pairs. This is known as “Law of independent assortment”. • Crossing yellow and green seeds produced all yellow seeds. Because yellow is dominant factor. • Each parent passes randomly selected copy (allele) of only one of these to its offspring. • The process of acquiring characters or traits from parents is called ‘Heredity’. • Each human cell contains 23 pairs of chromosomes. Out of these 22 pairs are called autosomes and one pair is called allosomes. Free distribution by A.P. Government 189 • Lamarck proposed that the acquired characters are passed to the offspring in the next generation. • Each species tend to produce large number of offsprings, but only the fittest can survive. • Homologous, analogous organs and embryological evidences explain evolutionary relationships. Some traits in different organisms would be similar because they are inherited from a common • ancestor. Fossils are evidences of ancient life forms or ancient habitats which have been preserved by natural processes. • Improve your learning 1. What are variations? How do they help organisms?(AS1) 2. One student (researcher) wants to cross pure tall plant (TT) with pure dwarf (tt) plant, what would be the F1 and F2 generations? Explain.(AS1) 3. One experimenter cut the tails of parent rats, what could be the the traits in offsprings? Do the 4. daughter rats contain tails or not? Explain your argument.(AS1) In a

mango garden a farmer saw one mango tree with full of mango fruits but with a lot of pests. he also saw another mango tree without pests but with few mangoes. But the farmer wants the mango tree with full of mango fruits and pest free. Is it possible to create new mango tree which the farmer wants? Can you explain how it is possible?(AS1) 5. Explain monohybrid experiment with an example, which law of inheritance can we understand? Explain.(AS1) 6. What is the law of independent assortment? Explain with an example?(AS1) 7. How sex determination takes place in human? Explain with example.(AS1) 8. Explain the Darwin’s theory of evolution ‘Natural selection’ with an example?(AS1) 9. What are variations? Explain with a suitable example.(AS1) 10. What variations generally have you observed in the species of cow?(AS1) 11. What are the characters Mendel selected for his experiments on pea plant?(AS1) 12. In what way Mendel used the word ‘Traits’- explain with an example.(AS1) 13. What differences Mendel identified between parent and F2 generation.(AS1) 14. Male is responsible for sex determination of baby – do you agree? If so write your answer with a flow chart.(AS1) 15. Write a brief note on analogous organs.(AS1) 16. How do scientists utilise the information about fossils?(AS1) 17. Mendel selected a pea plant for his experiments. Mention the reasons in your point of view.(AS2) 18. If the theory of inheritance of acquired characters proposed by Lamark was true how will the world be?(AS2) 19. Collect information on the inherited traits in your family members and write a note on it.(AS4) 20. With the help of given information write your comment on evidences of evolution.(AS4) Mammals have four limbs as do birds, reptiles and amphibians. The basic structure of the limbs is similar, though it has been modified to perform different functions. 21. Collect information about carbon dating method. Discuss with your physical science teacher.(AS4) 190 X Class Heredity - From parent to progeny 22. Draw a checker board show the law of independent assortment with a flow chart and explain the ratio.(AS5) 23. Explain the process to understand monohybrid cross

In this dihybrid cross, parents produce offsprings containing the factors for Characters (traits) of Yellow (YY), Round (RR), and wrinkled (rr), green (yy). These characters appeared independently without mixing with each other in F2 generation, which were produced by self pollination in F1 generation. Observe thc checker board given here carefully and note down different combinations of characters resulted from dihybrid cross. 1. RRYY, 2. RRYy, 3. RrYY, 4. RrYy, 5. RRYy, 6. RrYY, 7. RrYy, 8. RrYy, 9. RrYy are having Round and Yellow seeds. 1. RRyy, 2. Rryy, 3. Rryy have Round and Green seeds 1. Rryy, 2. rrYy, 3. rrYy have Wrinkled and Yellow seeds 1. rryy have Wrinkled and Green seeds R Y R y r y r Y RR YY RR Yy Rr Yy Rr Yy RR Yy RR yy Rr yy Rr Yy Rr Yy Rr yy rr yy rr Yy Rr YY Rr Yy rr Yy rr YY 3 :3 :1 Round yellow Wrinkled, yellow Round, green Wrinkled, green From the above results it can be concluded that the factors for each character or trait remain independent and maintain their identity in the gametes. The factors are independent to each other and passes to the offsprings (through gametes). In the inheritance of more than one pair of characters (traits), the factors for each pair of characters assorted independently of the other pair. This is known as “Law of independent assortment”. Mendel believed that every character or trait is controlled or responsible by a pair of factors. The factors which are responsible for a character or trait of an organism, now named as ‘genes’. The pair of genes which are responsible for a character are called as ‘alleles’. Alleles are of two types one is homozygous type (YY or TT) and the other is heterozygous (Yy or Tt). 192 X Class Heredity - From parent to progeny Chapter 9 Our environment - Our concern Everyone is familiar with one’s

own surrounding. It plays an important role in the survival of all organisms. The sum of physical and biological factors along with their chemical interactions that affect an organism is called environment. The living organisms maintain a balance with each other and to its biotic and abiotic factors. All components of biosphere interact in an organized manner with the organisms. This interaction assures an organism to survive that may result in gradual evolution of the organisms in the biosphere. The physical factors refers to abiotic factors (land, air, water sun light etc) and biological factors to biotic factors. The place where an organisms lives is called biosphere. One organism cannot completely defy the balance to suit one’s need. It would in some way or the other affect the balance in such a way that the survival of the organism affecting the damage would be at stake. You have understood the relationships between organisms and their food in earlier classes with the help of food chains and food webs. Food chains are interconnected and when we try to observe these connections among a number of food chains then it becomes a food web. As you know a food chain shows who eats what in a particular habitat. The arrows between each organism in the chain always point from the food to the feeder. If we want to show a food chain consisting of grass, snake, rabbit and hawk then connect the given fig-1: Food relationship Free distribution by A.P. Government 193 organisms by putting arrows and make a food chain. • Name the producer and consumers in the above food chain. • Try to guess what does the arrows marked by you indicate? • Identify at least four other food chains in your surroundings. Name the producers and different levels of consumers in those food chains. While identifying different food chains in your surroundings you will find that most of the food chains are quite short and they rarely consists of not more than four steps. You will also notice that as we move from producer to consumers (primary, secondary & tertiary) in a food chain the numbers of organisms at each level decreases. What type of relationships exist among the biotic components? In an ecosystem the energy rich food passes from producers to consumers stepwise, with respect to their (food) relationships. Producer Primary Consumer Secondary Consumer Tertiary Consumer Top Carnivore Examples Grass Grass Grass grasshopper Rabbit Goat frog Fox Man snake Wolf Hawk • Why do most of the food chains consist of four steps? • Why do the number of organisms get decreased as we move form producer to different level of consumers? To get answers

for the above question we have to recall some of the things which have been discussed in the earlier classes. In chapter 7 “Different Ecosystems” of class 8th it was mentioned that all organisms in an ecosystem derive energy from food to live and sunlight is the main source of the energy. Food chain shows that how the energy is passed from one organism to another. At each transfer a large proportion (80 to 90 percent) of energy is dissipated as heat produced during the process of respiration and other ways. Thus above three steps in a food chain very little energy is still available for living organisms to use. Within the biosphere there are a number of major ecosystems, the terrestrial ones being determined largely by the variations in climatic conditions between the Poles and Equator.In a similar way, if you climb a mountain such as Kilimanjaro in Equatorial Africa or Himalayan mountains in our country. You quickly go through a comparable system of ecosystems, 194 X Class Our environment - Our concern starting with tropical rain forest at the base and ending with perpetual snow and ice at the summit. The main climatic influences which determine these ecosystems are rainfall, temperature and the availability of light from the sun. For instance, forests are usually associated with high rainfall, but the type is influenced by temperature and light; the same applies to deserts which occur in regions where rainfall is extremely low. But these links are never as simple or rigid as the word ‘chain’ suggests. For example, aphids are eaten by many insectivorous birds in addition to warblers, and also ladybirds and other insects; hawks, on the other hand, prey upon a considerable variety of birds and small mammal-So the term food web is often a better one to use when being precise, as it suggests a far greater number of possible links and reflects the fact that the whole community is a complex inter-connected unit. Thus the original energy from the sun flows through the whole ecosystem from one tropic level to another. Let us observe the diagram (fig-2) which shows some of the feeding relationships amongst organisms living in deciduous woodland. You will see from the diagram that animals fit into special positions within the food web; each is described as its niche. For instance, there is a niche for insects such as aphids which suck up the juices of leaves. Another niche for insects such as caterpillars which have strong jaws for biting off pieces of a leaf and a niche for relatively large animals such as deer which browse

on the vegetation. All these animals feed on leaves but they differ both in size and in the manner in which they feed. So the term ‘niche’ denotes not only the animal’s position in the food web and what it eats, but also its mode of life. Just as a habitat is the place where an animal lives, so a niche describes its occupation the way it ‘goes about its business and earns its livings. fig-2: Food relationships Ecological pyramids Apart from the food chains pyramids are another type of representations which show flow of energy from one organism to another. You may have heard about pyramids of Egypt. The ecologists also used this idea of pyramid to show relationship among organisms in an existing Free distribution by A.P. Government 195 food chain. In short we can say that graphic representation of the feeding level (tropic level) of an ecosystem by taking the shape of a pyramid is called “Ecological pyramid”. It was first introduced by a British ecologist Charles Elton in 1927. In the ecological pyramid the producers (first trophic level) are represented at the base; and other successive trophic levels (primary, secondary and tertiary consumers) are represented one above the other with top carnivores at the tip. There are three types of pyramids; pyramid of biomass, pyramid of number, pyramid of energy. In this chapter we will try to discuss about the pyramid of number, biomass and energy. fig-3: Pyramid of Egypt Do you know? A pyramid is a structure whose shape is roughly that of a pyramid in the geometric sense; that is, its outer surfaces are triangular and converge to a single point at the top. The base of a pyramid can be trilateral, quadrilateral or polygonal shape. The square pyramids, with square base and four triangular outer surfaces, is a common version. Pyramid of numbers Biologists are not only interested in studying the food relationships which exists between living things, but also in comparing the numbers of organisms at each link in the chain. Here is an example of food web to make estimates of the comparative numbers of organisms present at each stage of chain. The comparison needs to involve the use of such terms as most, many, several, few and scarce. Is there any relationship between the numbers?Is there any comparison that could be made about the sizes of the organisms involved at each stage. Tertiary consumers Secondary consumers Primary consumers Producers fig-4: Pyramid

of numbers The number of organisms in a food chain can be represented graphically in a pyramid. Each bar represents the number of individuals at each trophic level in the food chain. At each link in a food chain, from the first-order consumers to the large carnivores, there is 196 X Class Our environment - Our concern normally an increase in size, but decrease in number. Let us observe fig-5, for example in a forest, the aphids are very small and occur in astronomical numbers, the ladybirds which feed on them are distinctly larger and not so numerous, the insectivorous birds which feed on the ladybirds are larger still and are only present in small numbers, and there may only be a single pair of hawks of much larger size than the insectivorous birds on which they prey. This relationship is best shown as a pyramid, which is upright. fig-5: Pyramid of numbers • Draw the pyramid of number for the following food chains (i) Banyan insects Woodpecker (ii) Grass rabbit wolf • • Are the pyramid of numbers having same structure in both of the above two cases as compare to the example given in the earlier paragraph? If there is a difference then what is it? Sometimes the pyramid of numbers does not look like a pyramid at all. This could happen if the producer is a large plant such as tree or if one of the organisms at any trophic level is very small. So keep one thing always in mind that whatever the situation, the producers still goes at the bottom of the pyramid. Pyramid of Biomass What is biomass? Biomass is organic material of biological origin that is ultimately derived from the fixation of carbon dioxide by trapping solar energy during photosynthesis. This includes trees, shrubs, crops, grasses, algae, aquatic plants, agricultural and forest residues and all forms of human, animal and plant waste. Any type of plant or animal material that can be converted into energy is called biomass. When these materials are used for energy production. They are known as bio fuels. The pyramid of biomass represents the relationships that exist between the quantity of living matter (biomass) at different trophic levels. In Free distribution by A.P. Government 197 terrestrial ecosystems, the biomass progressively decreases from producers to top carnivores. • Think why are the pyramids always upright? In an aquatic ecosystem, the biomass of phytoplankton is quite negligible as compared to that of the crustaceans and small herbivorous fish

that feed on these producers. The biomass of large carnivorous fish living on small fishes is still greater. This makes the pyramid of biomass inverted. It is found that 10 - 20 % of the biomass is transferred from one tropic level to the next in a food chain. A more accurate idea of food relationship may be obtained if the above pyramid of numbers is converted into a pyramid of biomass. This indicates the mass of plant matter which is used by the aphids to produce the mass of the of aphids population, the total mass of the ladybird population that could be supported by the aphids and so on through out the chain. In short we can say that biomass is food for the next trophic level in a food chain. Do you know? To reduce our dependence on fossil fuels (fuels formed by natural processes such as anaerobic decomposition of buried dead organisms, like coal, petrol etc.), and to help reduce air pollution, biomass can also be used as a source energy. Using biomass as fuel still puts carbon dioxide back into the atmosphere, but it is the same carbon dioxide taken from the air as the biomass was produced. The biomass in each trophic level is always less than the tropic level below. This is because biomass is a measure of the amount of food available. When animals eat, only a small proportion of their food is converted into new tissue, which inturn forms the food for the next trophic level. Most of the biomass that animals eat is either not digested, or used to provide the energy needed for staying alive. The biomass pyramid shows that animals are relatively inefficient in converting food into body tissues, the remaining part of the food being undigested is passed out as waste, or broken down in respiration to supply energy for such activities as feeding. Many animals convert not more than 10% of their food into their body fig-6: Pyramid of biomass 198 X Class Our environment - Our concern Man (1kg) Fish (10kg) Zoo plankton (100kg) Phyto plankton (1000kg) tissues, some herbivores even less. Let us take an example of a food chain which has been worked out in some detail- one in which we are involved when we eat fish. In this chain the plant plankton on the surface of waters of sea are food producers. They trap energy from sunlight. The animal plankton feed on the microscopic plants and the fish in turn feed on the animal plankton; we are at the end of the

chain when we eat the fish. The pyramid of biomass for this particular food chain will be as follows. In this particular food chain roughly 90% of the food is lost at each step. So it allows that it would take 1000 kg of plant plankton to produce 100 kg of animal plankton to form 10 kg of fish to produce 1 kg of human tissues, with a corresponding loss of the original plant potential energy that came from the sun. Thus we can conclude that the nearer an animal species is to the original plant source in a food chain the greater the amount of energy is available to the population of that species. In other words, the fewer the steps in the food chain, the more energy will be for the species at the top. Pyramid of Energy Food is the source of energy for organisms that are used in the growth and rebuilding of the parts of the body; that are constantly wearing out. The food by its nature is the chemical energy and by in its stored form, it is the potential energy. There are several mechanisms in organisms for continuous absorption of materials for the production of organic material, and for the release and conversion of organic material into inorganic form. Plants absorb the minerals from the soil. They are absorbed into the plant along with through roots. Photosynthesis is an essential process for the life. The energy of sunlight, carbon dioxide, and the water, which ofcourse needed by all living things, belong to nonliving things. As a result of photosynthesis, these can be made available in a suitable form of energy the food to the world of living things the animals or consumers, only by the green plants the producers. The food chains and food webs help in the transfer of the food and energy from the producers to different consumers. Animals obtain the minerals from the plant or animal food or both. Thus the mineral matter is constantly being removed from the earth to become a part of the plant, which may become a part of animal body. Curd that we eat is processed from milk, which comes from a cow, which in turn eats grass. The grass carries out photosynthesis and prepares food. In every case, the origin of food materials can be traced back to green plants. Free distribution by A.P. Government 199 Once the food is eaten, its energy follows a variety of pattern through the organisms. Not all the food can be fully digested and assimilated. Hair, feathers, insect exoskeletons, cartilage and bone in animal foods, cellulose and lignin in plant foods cannot be

digested by most animals. These materials are either egected by defaecation or regurgitated in pellets of indigested remains. Assimilated energy (that is not lost through respiration or excretion) is available for the synthesis of new biomass through growth and reproduction. Organisms lose some biomass by death, disease or annual leaf-drop, where they enter the detritus pathways of the food chain i.e., after the death and decomposition of organisms the materials flow back into the environment. The remaining biomass is eventually consumed by herbivores or predators and its energy there by enters the next higher trophic level in the ecosystem. Solar energy Producers (Chemical energy) Consumers (Chemical energy) Heat Heat The materials keep on cycling i.e. entering the living beings and through death and decay returning to the soil and atmosphere Such a flow of materials between organisms and their environment is called Cycling of materials or mineral circulation or Biogeochemical cycles (You have learnt in class IX ). Energy enters the producers in the ecosystem from the sun in the form of solar energy or solar radiation. No other organisms except green plants and Photosynthetic bacteria due to the presence of chlorophyll are capable of absorbing solar energy and converting it into chemical energy. From the producers, the chemical energy passes to the consumers from one tropic level to the next through food. At each tropic level, organisms use most of the food energy that they assimilate into their bodies to fulfill their metabolic requirements- performance of work, growth and reproduction. Because biological energy transformations are inefficient, a substantial proportion of metabolized food energy is lost, unused as heat. Only a small fraction goes to the eater at next trophic level. Organisms are no different from man-made machines in this respect. Most of the energy in gasoline is lost as heat in a car’s engine rather than being transformed into the energy of motion. In natural communities, energy 200 X Class Our environment - Our concern used to perform work or dissipated as heat cannot be consumed by other organism and is forever lost to the ecosystem. The effects of human activities on ecosystems In the earlier classes we have studied about different types of pollution as a result of human interventions in ecosystem. In this section we will try to understand that when we cut forest to grow food crops, how this activity brings harmful changes in ecosystem and affects organisms of each tropic level. Let us study a pond ecosystem to understand the components of environment, their interactions and effects of

human interventions in the following story. Story of Kolleru Lake Fresh water lakes provide the nutritional requirements of the world’s poorest people. One such lake is Kolleru which is no ordinary wetland. It is one of the largest fresh water lakes in India, existing between West Godavari and Krishna districts of the state of Andhra Pradesh. The catchment of the lake extends up to 6121 km2. The lake Kolleru discharges its excess water in to the Bay of Bengal through the twisty channel called Upputeru, which is about 65 km long. Nevertheless, the Kolleru wetland receives huge quantity of nutrient rich sediments from the flood plains of these rivers. In November 1999, the Government of Andhra Pradesh had declared the lake as Bird Sanctuary. This lake is hosting 193 species of birds and a variety of flora and fauna, including medicinal plants. It attracts migratory birds from northern Asia and Eastern Europe between the months of October and March and it is estimated as 20,00,000 birds per year. The lake was also an important habitat for an estimated 20 million residents. This largest sweet water lake has not only shrunk in size but faced great threat due to pollution in the last three decades as revealed by satellite pictures. The decrease in water area and muddy ground in the lake in flooding resulted fig-7: Kolleru Lake Free distribution by A.P. Government 201 Area in 2004 (Km2) 62.65 47.45 15.20 0 99.74 16.62 1.37 Classes Lake –water spread area Lake with sparse weed Lake with dense weed Table-1 Area in 1967 (Km2) 70.70 0 0 Lake-liable to flood in rainy season 100.97 Aquaculture ponds Rice fields Settlements Total 0 8.40 0.31 180.38 180.38 In which year lake-water spread area is more? Why? problems in the lake area. Observe the data given in the following table. • • How do you think weeds are more in the lake? • What are the reasons for decrease in lake area? • How do the above reasons lead to pollution? • How was the threat to the lake due to pollution discovered? • What could be the reason for the migration of birds to this lake? Being a profitable business, Aquaculture in Kolleru was started extensively in the eighties which later spread to other areas in the Krishna Godavari delta and attracted a large number of investors to

the area. In 1996, almost entire lake was brought under cultivation and bunds were constructed to keep water out to protect the crops. This divertion affected the natural flow system of the lake. The water holding capacity of the lake is also found significantly reduced. In due course of time activities such as agriculture and industries came along in ever growing intensity in the catchment area of the lake. Consequently, the drains and rivulets carry substantial quantity of various types of pollutants into the lake. The major sources of pollution are agricultural runoff containing residues of several agrochemicals, fertilizers, fish tank discharges industrial effluents containing chemical residues and different types of organic substances, municipal and domestic sewage. Excessive nutrient addition, especially from anthropogenic sources, led to explosive weed growth. Ex: Eichornia 202 X Class Our environment - Our concern As a result, the water of the lake turned more alkaline in nature, turbid, nutrient rich, low in dissolved oxygen (DO) and high in biochemical oxygen demand (BOD). Water borne diseases like diarrhoea, typhoid, amoebiasis and others are said to be common among the local inhabitants who are unaware of the state of pollution in the lake water. Vector borne diseases also increased. Prawn and fish have been found to be affected by diseases leading to some farms being abandoned. The lands thus abandoned are useless for agriculture too. Let us observe the following table showing different activities in the lake and their influence. Table-2 Agricultural Practices Aquaculture Industrial activities practices Human activities Problem Biological 1. Decreased Migratory birds 2. Population loss of flora and fauna 3. Pathogens Chemical 1. Eutrophication 2. Toxic contamination Physical 1. Siltation 2. Flooding - - + + + + + + - + + + + - - + - Legend: (+) means has influence on the mentioned problem (-) means has no influence on the mentioned problem • What are the factors that affected the number of migratory birds to decrease? • Do you find any relationship between biological and physical problems? • What are the reasons for chemical problems? • What happens if the dissolved oxygen reduce in lake water? • Is BOD of turbid and nutrient rich water high or low? What are it’s consequences? • People living in catchment area of Kolleru faced so many problems. Why? Free distribution by A.P. Government - + + - + 203 The Ministry of Environment and Forest (MoEF), Government

of India (GoI) constituted a committee “Operation Kolleru” to protect the lake. The objective of the programe is to bring back the ecological balance of Kolleru Lake which is a Gift of nature. Activity-1 Observe any water ecosystem in your surroundings and identify the different food chains and food web operating in this ecosystem. Write the following details in your notebook. Work Sheet 1. Names of the students in a group: _____________________ Date: _____________ 2. Name of the ecosystem: _____________________________________________ 3. Topography: ______________________________________________________ 4. Names / Number of plants (producers) identified: _________________________ 5. Names / Number of animals identified: __________________________________ 6. Identify the different types consumers and name them & mention their number below: Herbivores (Primary consumers): ___________________________________ Carnivores (Secondary consumers): __________________________________ Top carnivores(Tertiary): _________________________________________ 7. Food relationships among them: food habits / preferences: ___________________ 8. Show / draw the different food chains: __________________________________ 9. Showcase the food web: _____________________________________________ 10. List out all abiotic factors existing in the ecosystem: ______________________ ( A check list can be given, and asked to tick) 11. Is there any threat to the ecosystem? Yes/No _____________________________ If yes, what? and how? _____________________________________________ Suggest few remedial measures _______________________________________ When a forest is cut down and a food crop is grown in its place, a natural established ecosystem with its vast number of species in a state of dynamic equilibrium is replaced by a monoculture i.e. an unnatural concentration of a single crop of various kinds grown in different fields to provide cereals or roots, others grass for domestic animals. When we grow crops in large concentrations we also get food in abundant quantities. This situation is optimum for pest, parasites like fungi to grow on this food material. If the quantities of food are larger then 204 X Class Our environment - Our concern multiplication of pests and parasites is rapid and the resulting damage would be great. To avoid such happening we have tried to eliminate these competitors for the crops by using toxic chemicals (pesticides, herbicides, and fungicides). Many of them have been very effective, but their use has also created new problems. The perfect pesticide is the one which destroys a particular pest and is completely harmless to each and every other form of life, no such pesticide

exists or likely to be. • Name any two pesticides you have heard about? • How are the food grains and cereals being stored in your house and how do you protected them from pests and fungus? Pesticides are often indiscriminate in their action and vast number of other animals may be destroyed. Some of these may be predators which naturally feed on these pests, others may be the prey for other animals. Thus causing unpredictable changes in food chains and upsetting the balance within the ecosystem. A further danger is that some have a cumulative effect. Pesticides vary in their length of “life” as toxic substances. Some of the pesticides as well as herbicides are degradable. They are broken down into harmless substances in a comparatively short time, usually a year. Others are non degradable, and include those which contain mercury, arsenic or lead. These non degradable pesticides are potentially dangerous as they accumulate in the bodies of animals and pass right through food web. Being further concentrated at each step until animals at the top of pyramid may receive enough to do considerable harm. The process of entry of pollutants into a food chain is known as Bioaccumulation, whereas the tendency of pollutants to concentrate as they move from one trophic level to the next is known as Biomagnification. Let us observe the following research study on the effects of bio accumulation on human health. Seasonal Bioaccumulation of heavy metals in fish (cyprinus carpio) of Edulabad Water Reservoir (EBWR), Andhra Pradesh, India. The aquatic bodies such as water reservoirs and rivers surrounding the urban areas in India, pose a serious risk for survival of aquatic organisms due to water quality deterioration through excessive nutrient inputs, acidification, heavy metal contamination and organic pollution. The aquatic biota is being contaminated with heavy metals due to industrialization and anthropogenic activities. Free distribution by A.P. Government 205 Recently, fish are considered to be the bio indicators of metal contamination in environmental monitoring because fish species are strongly respond to stress conditions. fig-8: Edulabad Water Reservoir A study was undertaken to assess the enrichment of heavy metal such as Lead (Pb), Cadmium (Cd), Chromium (Cr), Manganese (Mn), Nickel (Ni) and Ferrum (Fe) contamination in Edulabad Water Reservoir (EBWR) which is located in urban areas of Rangareddy district of Andhra Pradesh, highly polluted with industrial and agricultural eff

luents. Cyprinus carpio (common scale carp) is a cheap and high proteinaceous fish used as food for human beings, living in polluted EBWR was chosen for the study. Heavy metals in water samples and its bioaccumulation in various tissues including liver, kidney and gill of the fish growing in the reservoir were analyzed along with glycogen and lipids contents. A parallel study was conducted in water samples and fishes collected from Bibi Nagar, Nalgonda district fresh water reservoir because it is less polluted, located 30 km near to EBWR in Andhra Pradesh. The results obtained in present study revealed that higher bioaccumulation and lower glycogen and lipid content in the fish of EBWR when compared to Bibi Nagar fresh water reservoir. The water and fish samples were collected in three seasons namely pre-monsoon (February-May), monsoon (June-September) and post monsoon (October-January) in each year. Three water samples were collected in three station thrice in each season from each tank in cleaned polythene bottles and tightly stopped and used for heavy metal analysis from June 2005 to May 2007. The metal concentrations in EBWR reservoir were found to be higher than Indian standard limits and exhibiting the following sequence, Fe > Pb > Cr > Ni > Cd. The heavy metals could find their way into the human food chain, we analyzed bioaccumulation of these metals in the fish tissues. The bioaccumulation of these metals in fish tissues were of the following trend, Cd > Cr > Fe > Ni > Pb. Higher bioaccumulation factors were found for Cd in liver, gill and kidney indicated the sensitivity of fish to this metal even at low concentrations. 206 X Class Our environment - Our concern It is found that the bioaccumulation was lesser in monsoon season than pre and post monsoon seasons. The heavy metals could find their way into human beings through food chain. This bio accumulation cause various physiological disorders such as hypertension, sporadic fever, renal damage, nausea, etc. It is concluded that unplanned urban settlements, combined with the proliferation of unorganized small-scale industries and the sewage lead to the contamination of the EBWR. Such increased bioaccumulation of heavy metals in fishes not only disturbs aquatic life but also increases health risk in human beings through food chain. • Where from pollutants enter to the water sources? • How can you say fishes living in water having heavy metals in their bodies? • Researchers

found that pollution levels increase during monsoon season. Why they found so? • Why did people also suffer from various diseases after consuming fishes living in local water reservoir? In many areas man has changed the natural ecosystems to a great extent by damming rivers, draining marshes, re-claiming land from the sea, cutting down forests, plough-ing up land and growing crops, and by building towns, cities, canals and motorways. These changes have greatly altered the communities of plants and animals living there. Consider the development of a large town, for example. There will be three kinds of change: a) Some plants and animal species will die out. b) Some will adapt to the new conditions sufficiently to survive in re- duced numbers. c) Some will benefit by the new conditions and will increase in numbers. Do you know? Minamata disease was first discovered in Minamata city in Kumamoto prefecture, Japan, in 1956. It was caused by the release of methyl mercury in the industrial wastewater from the Chisso corporation’s chemical factory, which continued from 1932 to 1968. This highly toxic chemical bioaccumulated in shellfish and fish in Minimata Bay and the Shiranui Sea, which, when eaten by the local populace, resulted in mercury poisoning. While cat, dog, pig and humans deaths continued for 36 years. Let us read the following story to know how cruel the human actvities are against the nature. Free distribution by A.P. Government 207 Sparrow campaign Any living organism can’t avoid crises since they are a normal part of life. However, none have ever encountered a disaster on the level of that which fell upon the Chinese Sparrows in 1958. The environmental crisis in question was not a natural one rather, it was manmade. In the entire history of sparrows around the world, they have never been hunted down as they were in China in 1958. fig-9: Sparrow in danger A radical campaign to rapidly increase China’s industrial output by mobilizing the country’s vast rural peasantry took place at this time. It was set in motion by the government with the intention to achieve rapid increase in industrial production that China would catch up with the rest of the civilized world. China had an agrarian society then. One of the most famous initiatives then was to form co-operatives or collectives up to 5,000 families and this initially yielded double the amount of crops grown. This initial success led

to ambitious goals for the following year, but the weather didn’t cooperate. Even though fewer crops were harvested, rural officials overstated the amount of grain for fear of not meeting their quotas. This over-reporting led to an imbalance between the demand and the supply. The sparrows were accused of pecking away at the supplies in warehouses at an officially estimated rate of four pounds of grain per sparrow per year. In the cities and the outskirts, almost half of the labour force was mobilized into the anti-sparrow army. fig-10: Sparrow campaign People started trapping, poisoning and killing sparrows in large numbers. Several free-fire zones were set up for shooting the sparrows. People would beat drums to scare the birds from landing, so the sparrows were forced to keep flying until they dropped dead from fatigue. Sparrow nests were torn down, eggs were broken, and nestlings were killed. Non-material rewards and recognition were offered to schools, work units and government agencies in accordance with the number of sparrows killed. Later some scientists who cut open the digestive systems of dead sparrows found that three-fourth of the contents were of insects harmful for crops and only one-fourth contained grains. The scientific findings 208 X Class Our environment - Our concern showed that sparrows were basically a beneficial bird for humans. Rather than being increased, crop yields after the campaign were substantially decreased. Though the campaign against sparrows ended it was too late. With no sparrows to eat the locust populations, the country was soon swarmed. Locusts coupled with bad weather led to the Great Chinese Famine. Use of pesticides against locust population further degraded the land. Instead of working in the fields, millions of farmers had to leave their villages to work for industries. Very small area was left under agriculture and food shortages became everyday occurrence. • What is the food chain that has been discussed in the above case? • How did the campaign disturb the food chain in the fields? • How did these disturbances affect the environment? • Is it right to eradicate a living organism in an ecosystem?How is it harmful? • Were the sparrows really responsible? What was the reason for the fall in crop production? • What was the impact of human activities on the environment? • What do you suggest for such incidents not to occur? • Read the poem “Manavi” in class VIII biology textbook and dis- cuss in your class. Steps towards prevention If we

arrows between each item in the food chain always point from the food to feeder. • Pyramid of numbers and pyramid of biomass are other ways to show food relationship and flow of energy among living things • A pyramid is a structure whose shape is roughly that of a pyramid in geometric sense. • • Pyramid of number shows the population of organisms at each trophic level in a food chain. Pyramid of biomass represents the available food as a source of energy at each trophic level in the food chain. • Biomass can also be used as a bio fuel. • Toxic material used to prevent the pest, fungus and other disease away from the food crop and grains do harms in many ways to ecosystem. • Bioaccumulation is the entering of pollutants in the food chain. • The tendency of pollutants to concentrate as they move from one trophic level to the next is known as Biomagnification. 210 X Class Our environment - Our concern • There are several alternatives for pesticides through which we can get more yields with less damage like rotation of crops, biological control, development of genetic resistant strains etc. Improve your learning 1. What happens to the amount of energy transferred from one step to the next in a food chain?(AS1) 2. What do pyramids and food chain indicate in an ecosystem?(AS1) 3. Write a short note on pyramid of number for any food chain? What can we conclude from this pyramid of numbers?(AS1) (ii) insect (i) tree (iii) woodpecker 4. What is biomass? Draw a pyramid of biomass for the given food chain- (AS1) (iv) hawk (i) grass leaves (ii) herbivores (iii) predators 5. How is using of toxic material affecting the ecosystem? Write a short note on bioaccumulation and biomagnifications.(AS1) 6. Should we use pesticides as they prevent our crop and food from pests or should we think of alternatives? Write your view about this issue and give sound reason for your answer.(AS1) If you want to know more about flow of energy in an ecosystem, what questions do you ask?(AS2) 7. What is a trophic level? What does it represent in an ecological pyramid?(AS1) 8. 9. What will happen if we remove predators from food web?(AS2) 10. Observe a plant in your kitchen garden, and write a note on producer- consumer relationship.(AS3)

11. What type of information do you require to explain pyramid of biomass? (AS4) 12. Draw a pyramid of numbers considering yourself as a top level consumer.(AS5) 13. Prepare slogans to promote awareness in your classmates about ecofriendly activities.(AS7) 14. Suggest any three programmes for prevention of soil pollution in view of avoiding pesticides.(AS7) Choose the correct answer 1. What does a food chain always start with (a) The herbivore (b) The carnivore (c) The producer 2. Which of the following do plants not compete for? (b) Food (a) Water (c) space ( (d) none of them ( (d) all above 3. Ban all pesticides, this means that a) Control on usage of pesticides c) promote eco friendly agricultural practices 4. According to Charles Elton b) prevention of pesticides d) stop bio chemical factories ( ( ) ) ) ) a) carnivores at the top of the pyramid c) No producers at the top of the pyramid d) a and c b) energy trapping is high at the top of the pyramid Free distribution by A.P. Government 211 Chapter 10 Natural Resources We learnt about natural resources like water, soil, forests, flora, fauna etc. and how to conserve them, in previous classes. We also learnt about the pollution of natural resources as a result of human activities. Natural resources are present in abundance, but do we really manage them properly? We shall study about human interventions affecting them and efforts that are being made to sustain and save them. Try to make an exhaustive list of natural resources in your locality. Try to find out about a particular resource especially one that is scarce in detail. Some questions below will help you to find out more about the resources. • Which resource in your locality is scarce? How does it affect you? • Was the resource present in abundance earlier? • How did it become scarce over the years? • What can you do as a step towards saving a resource? Let us study about two villages of Andhra Pradesh to make a study of an important resource and see what happens when it becomes scarce. Case I: Situation in two villages Vanaparthy and Vaddicherla of Warangal District A survey was conducted in two villages,Vanaparthy and Vaddicherla of Warangal District of Telangana region -the first with no-scarcity (good), and the second with scarce groundwater.Well census was carried out in the villages

in order to get a complete picture of well irrigation and its status as well as availability of water. Basic information on well irrigation 212 X Class Natural Resource was collected using a small questionnaire from all the well owners in the sample villages. Detailed information regarding various socio-economic aspects was collected using a detailed questionnaire from a sample of 25 households owning wells. Families in both the villages were asked to narrate the changes in groundwater situation during the last five years. There are no alternative sources of supply as against wells in Vaddicherla, whereas there is an existing tank that has been converted into a percolation tank, so that the water situation is much better in Vanaparthy. Do you know Percolation tanks are normally earthen dams with masonry structures where water may overflow. Construction materials consist of a mixture of soil, silt, loam, clay, sand, gravel, suitably mixed and laid in layers at the base or bed and sides. It is properly compacted to achieve stability. Outlets for surface irrigation are made and a cut-off trench is made below the earthen bund or dam with depth limited to one fourth of the height between bed level and full storage level. Percolation tank Basic features of the villages Vanaparthy and Vaddicherla are almost similar in terms of occupational pattern, cropping pattern, infrastructure and social services. In both the villages small farmers are in majority. Vanaparthy has the higher average household income. The main livelihood activity in these villages is cultivation and the primary source of irrigation is well. Household income is dependent on the status of groundwater. Vanaparthy has a higher proportion of its area under irrigation. The cropping pattern which influences average household income in these villages differs substantially.Though rain has not been consistent for a few years, farmers in these villages prefer growing paddy. Village Total Area (acres) Table-1: Area under irrigation Percentage Area Irrigated Number of Wells Sample Size Vanaparthy Vaddicherla 3791 2970 25 15 155 175 25 25 • What is the total irrigated area in acres, in Vanaparthy? Free distribution by A.P. Government 213 • If one needs to irrigate all the land in Vanaparthy, how many wells would be required? • Though the number of wells is less in Vanaparthy, the area under irrigation is more as compared to Vaddicherla. How is this possible? • Do you think the area under irrigation will change due to

rise in population? The change in area under cultivation, percentage change in number of wells and cropping pattern in 5 years as narrated by the people has been presented in table-2. The population in the villages have also gone up in a period of 5 years by nearly 10%. Table 2: Status after five years Village Percentage change in area under irrigation Percentage decline in number of wells Vanaparthy Vaddicherla -14 -30 -39 -68 Percentage change in area under crops Paddy Cotton Gingelly All Crops K R K R 11 -17 -17 -17 163 86 -22 -50 27 138 -05 -50 K stands for Kharif while R stands for Rabi. Negative values indicate loss/ decline, while positive ones show gain/rise. If the number of wells is 155 now, what was it 5 years back? • • What do you think ‘decline in number of wells’ represents? • How would crops be affected due to decline in the number of wells? • Compare table 1and2 and state what they tell us about the area under irrigation in both the villages? • Which village do you think is more affected? • What is the change in types of crops grown in the villages? Of late, most of the open dug wells were converted into bore wells that could reach greater depths of ground water zones and would also reduce loss of water by surface evaporation.Most of the open wells have dried up and water tables have gone down substantially during the last 5 years. During this time, 85 percent of the wells, mostly open, have dried-up in Vaddicherla while 45 percent of the wells dried-up in Vanaparthy. • If 45 percent of wells have dried up in Vanaparthy, and there is 39 percent decline in number of wells, what percentage of wells do you think have been converted to bore wells? 214 X Class Natural Resource • By comparing the two villages, find out where greater number of wells dried up? What methods would have saved the wells in other village? • Which type of farmers, those having small land holdings or those with large land holdings are most affected when wells dry up? If water resource becomes scarce, will it affect the nature of soil in an area? • • As wells dry up, how are people in the area dependent on the well affected? • Why do you think water became scarce mainly in Vaddicherla? Water is usually pumped out of wells and bore wells using electricity. Farmers

with small land holdings or small farmers tend to spend more money per well in terms of installation of pump sets and pipeline connections to farms(or capital expenditure) as well as running costs towards maintenance, electric charges etc. On per acre basis, both capital and running costs are the lowest in Vanaparthy (no-scarcity village) and highest in Vaddicherla (scarcity village). Table 3: Annual expenditure on well irrigation for small and large farmers(2002) Village Type of Farmer Depth of bore well (in feet) Percentage area irrigated per well Vanaparthy Large Small Vaddicherla Large 130 - 200 110 - 180 90 - 300 Kharif Rabi 2.50 1.24 2.00 1.13 1.53 0.87 Small 60 - 200 0.99 0.46 Total cost of well irrigation per acre per year in rupees 25000- 70000 25000- 65000 22000- 50000 20000- 45000 Is the availability of water resource same for a small and a large farmer? • • Do you think the availability should be same for everyone in an area? • A well irrigates more area in Kharif season as compared to Rabi, how is it possible? • How should a farmer utilize such a condition? • If a well can irrigate 2.5 percent of cultivable land, how many wells would irrigate whole of the land? • Which factor has a greater effect on expenditure, number of wells or depth of a well? • What is the total expenditure on a whole cultivable land owned by a small farmer in Vaddicherla?How do you think a small farmer meets this expenditure? • What could help the small farmer reduce expenditure? (Hint: think of crops that require less water) Free distribution by A.P. Government 215 • Do you think increasing the depth of bore well is a good solution for increasing total land area under irrigation? Why/Why not? Do you know? Because of varying monsoon behaviour in recent years, there is a pressure on groundwater utilization. Indiscriminate tapping of groundwater in the State by too much drilling and construction of deep tube wells and bore wells, have resulted in over exploitation and depletion of groundwater resources in certain areas. Average fall of water level was around 3 meters in the State during the period of 1998- 2002. Table 4: Income on crops Village Type of Farmer Net income per acre in Rupees Paddy Paddy Cotton Gingelly Kharif Rabi

Total income per acre year in rupees Vanaparthy Large Small Vaddicherla Large Small 8200 8700 4900 7046 8490 10889 10698 5970 4000 9128 7380 3031 3300 3110 3595 2650 25100 29535 24263 22189 • Which crop is most profitable for a small farmer in Vaddicherla? • What is the difference between a small farmer in Vanaparthy and Vaddicherla? • Which crop could replace paddy and be profitable as well for a small farmer in Vanaparthy? • Though we know that paddy consumes maximum water, why do you think farmers still like to grow paddy? • What is the impact of a depleting resource upon the farmers? • Do you think the income of a small farmer in Vaddicherla is sufficient enough to meet his expenditure? • What are the major causes of pitiable condition of small farmers at Vaddicherla? • Do you think farming as an occupation is profitable for the small farmer in Vaddicherla? • Would the farmer have to look for other kind of occupations to meet his ends? • How did the availability of water affect a small farmer at Vaddicherla? A project of the Centre for world solidarity(Secundrabad, A.P) that addresses sustainability of ground water intervened to help in recharging wells that were drying up in the villages. 216 X Class Natural Resource They encouraged more water sharing among farmers. They formed groups of farmers including large and small ones who would use the same water resource. Farmers were also motivated to use irrigation techniques like drip irrigation, sprinklers etc.(collectively called as micro irrigation techniques). Construction of soak pits to tap rainwater optimally was carried out as community efforts. Soakpits helped in recharging dried up bore wells. Dykes or barriers, nearly 30 cm thick of brick-cement or stone cement barrier, extending down to the compact bedrock, with mud or clay fillings were built in underground streams to tap ground water optimally. • How can wells be recharged? • How would recharging dried up wells help farmers of Vaddicherla? • What does the case tell us about a water resource and its effect on farmers? Water for all Out of all the water on Earth, salt water in oceans, seas and saline groundwater make up about 97% of it. Only 2.5–2.75% is fresh water, including 1.75–2

% frozen in glaciers, ice and snow(nearly two thirds of the available freshwater), 0.7–0.8% as fresh groundwater and soil moisture, and less than 0.01% of it as surface water in lakes, swamps and rivers. Though it is a meagre portion of the whole, if used judiciously, shall last for a long time. • How do you think we can use water judiciously? • Why were farmers at Vanaparthy at a better state than those at Vaddicherla? • How did farmers of Vaddicherla and Vannaparthy recharge their ground water resources? Do you know? In ancient times, village boundaries were decided upon on a watershed(land between water sources usually of two rivers or streams) basis fixed at the common point of the drainage system in between two villages by the expert farmers in the village. Such boundaries were socially acceptable to all the members of the system. Case II: A Study of Kothapally Village, an example of water management effort This tells us how people in the village through proper guidance could make optimum use of available water in the village. Free distribution by A.P. Government 217 A survey of Kothapally village indicated that initially: (i) dry land areas were more extensive than irrigated land; (ii) literacy was low; (iii) labour was scarce; (iv) more fertilizers/pesticides were used on small farms (v) crop yields were low, (vi) there was not even a single water harvesting structure in the village. Interventions to enhance productivity and income (Soil and water conservation measures) International Crop Research Institute for Semi-Arid Tropics( ICRISAT) educated villagers by large and provided technical support for cost-efficient water storage and soil conservation structures. The measures were community as well as individual farmer-based. These helped to restore some resources and conserve others so that they may never be depleted. Thus sustainable management was carried out. What is ICRISAT, where is it? What are it functions? Discuss with your teacher and prepare on it. Community-based interventions Fourteen water storage structures (one earthen and 13 masonry dams) with water storage capacity of 300 to 2 000 m3were constructed. 60 minipercolation pits and field bunding on 38 hectare were completed. fig-1: Communitybased masonry dam fig-2: Contour field bunding Do you know? Sri

P. Government 219 was undertaken by the farmers. 2500 fruit trees and teak plants were planted. • What other ways of restoration of a resource does the Kothapally case tell us about? • What are some common means of restoration and conservation of water resource that we came across in the cases studied so far? According to a survey conducted in the year 2004 Total amount of water availablein Andhra Pradesh - 3814 thousand - million cubic feet (TMC) Total amount utilised Irrigation Domestic use Industries Power generation Amount required for utilisation by 2025 is 3989TMC of which 3,814TMC is for irrigation, 122TMC for domestic use, 51TMC for industries and 2TMCis for power generation. • What do you think will happen if we do not take care of the sources 2300 TMC of which 2268 TMC 21 TMC 10 TMC 1 TMC of water? • How do you think we will meet our requirements in future? • Do you think we would have to depend upon other states or perhaps other countries as well? • Could the amount of water used for irrigation in Andhra be reduced? How? • Does cropping pattern have any role to play in reduction of water utilisation? (Hint:Think of the case of Vaddicherla and Vanaparthy). • Do you think one needs laws for distribution of water and its use? Why/Why not? Source of irrigation water in Andhra Pradesh • How much per cent of area do you think is irrigated by other sources of water? We have seen that major consumption of water is in the farming sector. In spite of some major rivers like Godavari and Krishna, the major source of irrigation is groundwater. • Why is it important to recharge the ground water sources? • Why do the rivers fail to benefit the state to an extent they should have? 220 X Class Natural Resource • Since ground water resources are getting depleted at a fast pace what are the alternatives? • River Godavari fails to provide water for the projects like Sri Rama Sagar in our State due to over usage of water by some other state. How should and countries work to provide enough for all? states Other sources 5% Tanks 15% Cannals 37% Ground water 43% fig-6: Sources vs area under irrigation It is comforting to think water is a renewable resource but we must know what limitless exploitation of a resource can lead to. According to United Nations Development Programme, “Water resource in

an area, where annual water supply drops below 1700 m3 per person, is becoming scarce.” The food and Agriculture Organisation of the United Nations has predicted that by 2025, 1.8 billion people will be living in countries or regions with absolute water scarcity. Activity-1 Study the different ways in which water is used, misused and recycled in the area where you stay. Prepare a questionnaire with the help of your friends and teacher and study at least five households in your locality for the same. Also explore and discuss ways to provide water for all. Natural resources around us The Earth’s natural resources include air, water, soil, minerals, fuels, plants, and animals. Conservation is the practice of caring for these resources so all living things can benefit from them now and in the future. All the things we need to survive, such as food, water, air, and shelter, come from natural resources. Some of these resources can be replaced after they are used and are called renewable resources. Other resources, such as fossil fuels, cannot be replaced at all. Once they are used up, they are gone forever. This is because it takes a long time for their formation while their consumption occurs very quickly. These are nonrenewable resources. People often waste natural resources. Animals are overhunted. Forests Free distribution by A.P. Government 221 are cleared, exposing land to wind and water damage. Fertile soil is exhausted and lost to erosion because of poor farming practices. Fuel supplies are depleted. Water and air are polluted. If resources are carelessly managed, many will be used up. If used wisely and efficiently, however, renewable resources will last much longer. Through conservation, people can reduce waste and manage natural resources wisely. Water use restrictions are in place in many regions of the world. In Australia, in response to chronic shortage resulting from drought, restrictions are imposed on activities like, watering lawns by using sprinkler systems, washing vehicles, using hose pipes to clean paved areas, and refilling swimming pools. The population of human beings has grown enormously in the past two centuries. Billions of people use up resources quickly as they eat food, build houses, produce goods and burn fuel for transportation and electricity. The continuation of life as we know depends on the careful use of natural resources. The need to conserve resources often conflicts with other needs. For some people, a forest area may be a good place to put a farm. A timber company may want to harvest the area’s trees

for construction materials. A business company may want to build a factory or shopping mall on the land. All these needs are valid for us, but sometimes the plants and animals that live in the area are forgotten. The benefits of development need to be weighed against the harm to animals that may be forced to find new habitats, the depletion of resources we may want in the future (such as water or timber), or damage to resources we use today. • Think of any resource from your surrounding other than water that you cannot do without and write a short account on its sources, availability and condition. Development and conservation can coexist in harmony. When we use the environment in ways that ensure we have resources for the future, it is called sustainable development. There are many different resources we need to manage and conserve and main order to live sustainably. • What would you do to motivate others to manage an important resource in your locality? • How did the villagers in Kothapally resort to sustainable management? fig-7: Sustaibable development 222 X Class Natural Resource Forest: an important renewable resource Why do you think forests are important? Every continent except Antarctica has forests. Which are rich habitat for plants and animals. Forests serve as a lung for the world and a bed of nutrients for new life to prosper. They provide us innumerable products and in an urge to extract them we indiscriminately destroy them. People clear forests to use the wood, or to make way for farming or development. Each year, the Earth loses about 36 million acres of forest to deforestation an area about half the size of our state. Deforestation destroys wildlife habitats and increases soil erosion. It also releases greenhouse gases into the atmosphere, contributing to global warming. Deforestation accounts for 15 percent of the world’s greenhouse gas emissions. Deforestation also harms the people who rely on forests for their survival, hunting and gathering, harvesting forest products, or using the timber for firewood. Sustainable forestry practices are critical for ensuring resources well into the future. Perhaps the bishnoi’s of Rajasthan could tell us how. As we recall brave Amrita Devi and her daughters, followed by villagers who clung to trees in the forest surrounding their village and laid down their lives to save them, we are faced with a realization about how great a movement towards conservation can be. They were protesting against the Kings’ order to collect wood for the construction of his palace and defending the pledge of peaceful coexistence taken by them as a bishnoi

. It is a set of 29 rules to conserve natures’ resources that every bishnoi vows to protect. You have also studied about the Chenchu tribe of our state and are aware of how carefully they extract resources from nature and help revive it. Some sustainable forestry methods include using low-impact logging practices, harvesting with natural regeneration in mind, and avoiding certain logging techniques, such as removing all the high-value trees or all the largest trees from a forest. Trees can also be conserved if consumers recycle. People in China and Mexico, for example, reuse much of their wastepaper, including writing paper, wrapping paper, and cardboard. If half the world’s paper were recycled, much of the worldwide demand for new paper would be fulfilled, saving many of the Earth’s trees. We can also replace some wood products with alternatives like bamboo, which is actually a type of grass. Free distribution by A.P. Government 223 Soil Soil is vital to food production. We need high-quality soil to grow the crops that we need. Soil is also important to plants that grow in the wild. Many other types of conservation efforts, such as plant conservation and animal conservation, depend on soil conservation. Poor farming methods, such as repeatedly planting the same type of crop in the same place, deplete nutrients in the soil. Soil erosion by water and wind increases when farmers plough up and down hills. One soil conservation method is called contour strip cropping. Several crops, such as corn, wheat, and clover, are planted in alternating strips across a slope or across the path of the prevailing wind. Different crops, with different root systems and leaves, help to prevent soil erosion. The practice of removing individual plants or small groups of plants leaves other plants standing to anchor the soil is called selective harvesting. Biodiversity Biodiversity is the variety of living things that populate the Earth. The products and benefits we get from nature rely on biodiversity. We need a rich mixture of living things to provide foods, building materials, and medicines, as well as to maintain a clean and healthy landscape. When a species becomes extinct, it is lost to the world forever. Scientists estimate that the current rate of extinction is 1,000 times the natural rate. Through hunting, pollution, habitat destruction, people are speeding up the loss of biodiversity at an alarming rate. It’s hard to know how many species are going extinct because the total number of species is unknown. Scientists

discover thousands of new species every year. For example, after looking at just 19 trees in Panama, scientists found 1,200 different species of beetles 80 percent of them unknown to science at the time. Based on various estimates of the number of species on Earth, we could be losing anywhere from 200 to 100,000 species each year. We need to protect biodiversity to ensure plentiful and varied food sources. Biodiversity is important for more than just food. For instance, we use between 50,000 to 70,000 plant species for medicines worldwide. A lawn in a colony is usually a pleasant sight but do you know that a lot of species of plants are completely destroyed to grow the type of grass on the lawn? Moreover the grass usually grown has been brought from other countries. 224 X Class Natural Resource • Observe a lawn in your area (if you have one) and see how it is maintained. Find out from the gardener the different types of plants that he removes from time to time. • Do you think a farmer does the same thing on his farm? Activity-2 Find out how many types of insects are present in and around your house. Do you find the same type of insects in all seasons? Make a chart of insect types(in case you don’t know their names give them one or take the help of your elders) and note their occurrence for at least a week in each season. Repeat for other seasons.Study for a year and find out when you have highest varieties of them. Study them for subsequent years to see if they have disappeared. Some governments have established parks and reserves to protect wildlife and their habitats. They are also working to abolish hunting and fishing practices that may cause the extinction of some species. Fossil Fuels Fossil fuels were produced from the remains of ancient plants and animals. They include coal, petroleum (oil), and natural gas. • What do fossil fuels provide us? • Why do we need to conserve them? Apart from its use in vehicles, many of the products we use today are made from petroleum. These include plastics, synthetic rubber, fabrics like nylon, medicines, cosmetics, waxes, cleaning products, medical devices etc. Natural gas 7% Oil 24% Nuclier 1% Waste 24% Other 2% Coal 42% fig-8: Percentage consumption of some resources in India We need to conserve fossil fuels so we don’t run out of them. However, there are other good reasons the pollution caused by them when burnt, to limit our fossil fuel

use. Scientists are exploring alternatives to fossil fuels. They are trying to produce renewable biofuels to power cars and trucks. They have successfully produced electricity using the sun, wind, water etc. Free distribution by A.P. Government 225 Do you know? Seeds from the Jatropha curcas plant are used for the production of bio-fuel, a crucial part of India’s plan to attain energy sustainability.Andhra Pradesh has entered into a formal agreement with Reliance Industries for Jatropha planting. The company has selected 200 acresof land at Kakinada to grow Jatropha for high quality biodiesel. Jatropa Jatropa seed Everyone can help conserve fossil fuels by using them carefully. • Turn off lights and other electronics when you are not using them. • Purchase energy-efficient appliances. • Walk, ride a bicycle and use public transportation whenever possible. It is better to prefer public transport system like bus or train instead • of travel in personnel vehicles. Discuss in your class how this helps to the society. • Collect information about solar, wind, tidal and water power and prepare a scrap book. • Ask your teacher about nuclear energy and its impacts on ecosystem. Minerals Earth’s supply of raw mineral resources is in danger. Many mineral deposits that have been located and mapped have been depleted. As the ores for minerals like aluminum and iron become harder to find and extract, their prices go up. This makes tools and machinery more expensive to purchase and operate. Many mining methods, such as mountaintop removal mining (MTR), devastate the environment. They destroy soil, plants, and animal habitats. Many mining methods also pollute water and air, as toxic chemicals leak into the surrounding ecosystem. • Think why distaters like Uttarakhand happend? Activity-3 Now a days people are revolt against mining. Collect any such incident of our state or neighbouring states from your school library or news papers and conduct a seminar on it’s impact. 226 X Class Natural Resource Less wasteful mining methods and the recycling of materials will help conserve mineral resources. In Japan, for example, car manufacturers recycle many raw materials used in making automobiles. In the United States, nearly one-third of the iron produced comes from recycled automobiles. Conservation- A vital concern “The interest in conservation is not a sentimental one but the discovery of a truth well known to our ancient sages. The Indian tradition teaches us that all forms of life - human, animal and plant are so closelyinter

-linked that disturbance of one gives rise to imbalance in the other”. (By Srimati Indira Gandhi, while launching the world conservation strategy in India on6th March 1980). In the 1960s most countries lived within their ecological resources. But the latest figure shows that today three-quarters of the human population live in countries which consume more than they can replenish. The issue of replenishment is large yet we have our individual roles. Small steps could become great efforts at conservation. What does the Kothapally experience tell us about step towards management and conservation? You may have already come across the three R’s to save the environment. They are Reduce: That is useless if you can afford to say water, by repairing leaky taps and avoiding a shower or switching off unnecessary lights and fans. Think of other things that you could reduce usage of. • Do you think it is necessary to have a lot of lighting for decoration during celebrations? Reuse: things that you often tend to throw away, like paper and wrapping papers. This would save plants and minimise pollution. • What other things could you reuse to save our resources? Recycle: may not always be a very good option as recycling plastic is a tricky process and can cause havoc. The chief problem lies in plastics’ complexity. There are as many types of plastic as their uses. Since each type can only be recycled with its own kind, plastics need to be carefully sorted before they can be processed. • Why should one sort wastes carefully before discarding them from home? Free distribution by A.P. Government fig-9: Bag from waste material fig-10: Recycling logo 227 • Often we keep a plastic bag in our dustbins to discard waste, is it a good practise? Conservation Groups Governments enact laws defining how land should be used and which areas should be set aside as parks and wildlife preserves. Governments also enforce laws designed to protect the environment from pollution, such as requiring factories to install pollution-control devices. Finally, governments often provide incentives for conserving resources. Many international organizations are also dedicated to conservation. Members support causes such as saving rain forests, protecting threatened animals, and cleaning up the air. The International Union for the Conservation of Nature (IUCN) is an alliance of governments and private groups founded in 1948. The IUCN works to protect wildlife and habitats. In 1980, the group proposed a world conservation strategy. Many governments have used the IUCN model to develop their own conservation plans

. In addition, the IUCN monitors the status of endangered wildlife, threatened national parks and preserves, and other environments around the world. Take Kothapally village as an example; discuss the role of organizations involved in conservation and that of the villagers. • Can international, national or state organizations alone manage a resource? Who are all involved in the whole process of management? Suggest some ways in which you and your friends would like to manage a resource? • • Are we also an important resource of nature? How? • Find out the usage of water in Litres per day in your home? Do you actually require that much water and how much water is enough in accordance with National standards? It is time to know our responsibilities to protect natural resources for future generations. Key words Percolation tank Micro-irrigation Borewells Sustainabledevelopment, Biofuels Contour strip farming, Dyke Management. 228 X Class Natural Resource What we have learnt • Management of resources is essential for their conservation and restoration. • Resources are usually local specific and local people need to have control over them. • People need to be motivated to reduce pressure on the environment by reducing utilization of resources and reusing some of them. • We must use our resources judiciously especially fossil fuels, coal and petroleum as they will be ultimately exhausted. • Interstate and intercountry disputes should not hamper availability of a resource. Improve your learning 1. The BP statistical Review of World Energy in June measured total global oil at 188.8 million tonnes, from proved oil resources at the end of 2010. This is only enough for oil to last for the next 46.2 years. What measures should be taken to conserve oil? What will happen if we do not conserve it?(AS1) 2. Here is a news strip, read it carefully and answer the following questions Villagers oppose sand mining project Santhabommali (Srikakulam): People of more than 20 villages in two mandals of Srikakulamhave raised a banner of revolt against the proposed beach sand mining project by a private company and threatened to intensify their agitation if the government does not cancel the project. The sand mining is being taken up to extract rich minerals from the area. The villages are located around the forest belt were mining was initiated.(AS1) i) Do you think the villagers are doing a right thing to agitate? Why? ii) What resources are the villagers trying to save by their agitation? iii) Will the villagers

be benefitted by the rich minerals extracted from sand? iv) Why does the private company want to carry out mining in the area? v) Does the government have any role to play? vi) How will mining in that piece of land affect people of the area? 3. What is sustainable development?How is it useful in natural resource management?(AS1) 4. Write a detailed note on management of a natural resource.(AS1) 5. Suggest some ways of reusing a resource in your locality?(AS1) 6. Why should we conserve forests and wild life?(AS1) 7. Suggest some approaches towards the conservation of forests.(AS1) 8. Natural resources are decreased more rapidly. Guess what will be the consequences?(AS2) 9. Prepare a questionnaire to conduct interview it petrol filling station personnel about consuption of fossil fuels?(AS2) 10. Prepare model for rain water harvesting or energy saving are soil management. That reflect your innovative thoughts. (AS3) 11. List out names of villages farmers and procedure followed for restoration of any natural resource in your area.(AS4) Free distribution by A.P. Government 229 12. You might have heard the Natural Gas drillings near Kakinada by ONGC(Oil and Natural Gas Corporation). Collect information and prepare a note on the status of Gas production at the basin.(AS4) 13. Does your village or nearest city have a mechanism in place for recycling these waste materials? Find out how it is done and write in detail.(AS4) 14. Collect any graph that shows oil (petroleum) consumption in India.(AS4) i) Does the production meet consumption in India? ii) During which period of time shows highest increase in consumption rate? iii) Why will you say happened to production from past ten years, for example 2004 to 2014? iv) Suggest some ways to bring down consumption of petroleum. 15. Proper utilisation of natural resources is the way to show gratitude to our nation. Can you support this statement? Give your argument.(AS6) 16. Crop selection and cultivation should be based on availability of water. Prepare a slogun to make aware of farmers about this?(AS7) Fill in the blanks................... plants are used for production of bio fuel. 1. 2. Bio diversity is important for more than just food and for................ also. 3. Example for non renevable resource is.......................... 4. 5. Cultivation of paddy is

suitable for................ areas. Choose the correct answer........................ is the alternative method to prevent ground water depeletion. 6. Percolation tanks helps to ( ) (a) supply water for agriculture (c) preserve rain water (b) increase ground water level (d) prevent overflow of water from tanks during rainy season 7. Which of the following practice is suitable to farmer with less water resources ( ) (i) select shortterm crops, (ii) cultivate comercial crops, (iii) adapt drip system, (iv) crop holiday (c) i, iv (a) i, ii (b) i, ii, iii (d) iii, iv 8. Which of the fossil fuel reserves decrease more rapidly in India (a) natural gas (d) all 9. Huge amount of toxic chemicals leak into the surrounding eco system because of (c) petrolium (b) coal ( ( (a) industries (b) mining (c) pestisides (d) modern technology 10. Sustainable development means (a) prevention of wastage (c) development without damaging (d) high yieldings in less time (b) stable growth ( Courtesy- Case 1: V. Rantha Reddy, Centre for Economics and Social Studies, Hyderabad. Case 2: Paper on water management in Andhra Pradesh by Dr. M.D. Reddy, Water Technology Centre ANGAR Agriculture Univeristy, Hyderabad. ) ) ) 230 X Class Natural Resource Community College Robert Wise, The University of Wisconsin Oshkosh Vladimir Jurukovski, Suffolk County Community College Jean DeSaix, The University of North Carolina at Chapel Hill Jung Choi, Georgia Institute of Technology Yael Avissar, Rhode Island College Curriculum Framework for AP® Biology Big Idea 1: The process of evolution drives the diversity and unity of life. Enduring understanding 1.A. Change in the genetic makeup of a population over time is evolution. 1.A.1. Natural selection is a major mechanism of evolution. Chapter/Key Concepts 5.3, 18.1, 18.2, 19.1, 19.2, 19.3, 21.2, 23.5 1.A.2. Natural selection acts on phenotypic variations in populations. 7.3, 7.6, 18.2, 19.2, 19.3, 36.5 1.A.3. Evolutionary change is also driven by random processes. 19.1, 19.2

1.A.4. Biological evolution is supported by scientific evidence from many disciplines, including mathematics. 2.1, 5.2, 8.2, 11.1, 14.1, 17.1 18.1, 19.3 Enduring understanding 1.B. Organisms are linked by lines of descent from common ancestry. Chapter/Key Concepts 1.B.1. Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. 3.4, 4.3, 4.6, 8.2, 15.3, 13.2, 14.1, 15.5, 18.1, 20.1, 20.2 1.B.2. Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested. 14.4, 20.1, 20.2, 20.3 Enduring understanding 1.C. Life continues to evolve within a changing environment. Chapter/Key Concepts 1.C.1. Speciation and extinction have occurred throughout the Earth's history. 14.4, 18.2, 20.1, 38.1 1.C.2. Speciation may occur when two populations become reproductively isolated from each other. 18.2, 19.2, 23.5 1.C.3. Populations of organisms continue to evolve. 7.3, 7.6, 18.1, 18.3, 19.1, 19.2, 20.1, 20.2, 23.5 Enduring understanding 1.D. The origin of living systems is explained by natural processes. Chapter/Key Concepts 1.D.1. There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. 8.2, 18.1, 20.1, 21.1, 20.3 1.D.2. Scientific evidence from many different disciplines supports models of the origin of life. 8.2, 18.1, 20.2, 28.1 This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Preface 5 Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. Enduring understanding 2.A. Growth, reproduction and maintenance of the organization of living systems require free energy and matter. Chapter/Key Concepts 2.A.1.

All living systems require constant input of free energy 2.A.2. Organisms capture and store free energy for use in biological processes. 6.1, 6.2, 6.3, 6.4, 6.7, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 8.2, 23.1, 23.5, 36.3, 37.2 3.2, 4.3, 6.1, 6.4, 6.5, 7.1, 7.2, 7.3, 7.4, 7.4, 7.5, 7.6, 8.1, 8.2, 8.3, 9.2, 22.1, 22.2, 23.1, 23.5, 37.2 2.A.3. Organisms must exchange matter with the environment to grow, reproduce and maintain organization. 2.1, 2.2, 3.3, 4.2, 4.6, 6.1, 6.8, 22.4, 22.5, 23.5, 25.8, 37.3 Enduring understanding 2.B. Growth, reproduction and dynamic homeostasis require that cells create and maintain internal environments that are different from their external environments. Chapter/Key Concepts 2.B.1. Cell membranes are selectively permeable due to their structure. 3.2, 3.3, 5.1, 5.2, 5.3, 5.4, 8.3 2.B.2. Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes. 2.3, 3.3, 5.2, 5.3, 5.4 2.B.3. Eukaryotic cells maintain internal membranes that partition the cell into specialized regions. 3.3, 4.2, 4.3, 4.4 Enduring understanding 2.C. Organisms use feedback mechanisms to regulate growth and reproduction, and to maintain dynamic homeostasis. Chapter/Key Concepts 2.C.1. Organisms use feedback mechanisms to maintain their internal environments and respond to external environmental changes. 2.C.2. Organisms respond to changes in their external environments. 5.2, 5.3, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 8.2, 10.1, 11

.1, 21.1, 23.5, 24.3, 28.3 2.1, 6.4, 7.5, 7.6, 22.5, 23.5, 26.3, 26.5 Enduring understanding 2.D. Growth and dynamic homeostasis of a biological system are influenced by changes in the system's environment. Chapter/Key Concepts 2.D.1. All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy. 2.1, 2.2, 7.1, 7.4, 7.5, 7.6, 8.2, 15.2, 15.3, 17.3, 21.1, 22.4, 35.1, 37.1 2.D.2. Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments. 4.3, 5.2, 6.1, 18.2, 21.1, 25.1, 32.1, 32.3, 34.1 2.D.3. Biological systems are affected by disruptions to their dynamic homeostasis. 3.2, 22.3, 22.5, 23.1, 28.3, 38.2 2.D.4. Plants and animals have a variety of chemical defenses against infections that affect dynamic homeostasis. 23.6, 33.1, 33.2 Enduring understanding 2.E. Many biological processes involved in growth, reproduction and dynamic homeostasis include temporal regulation and coordination. Chapter/Key Concepts 2.E.1. Timing and coordination of specific events are necessary for the normal development of an organism, and these events are regulated by a variety of mechanisms. 10.2, 10.3, 14.3, 23.5, 30.1, 32.3, 34.1, 34.6 2.E.2. Timing and coordination of physiological events are regulated by multiple mechanisms. 6.8, 10.1, 10.2, 15.3, 22.3, 23.2, 24.1, 30.6, 36.1, 36.2, 36.3, 36.4, 36.5, 43.6, 43.7 6 Preface Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce and to maintain dynamic homeostasis. 2.

E.3. Timing and coordination of behavior are regulated by various mechanisms and are important in natural selection. 11.1, 21.2, 23.5, 30.6, 35.2, 45.7 Big Idea 3: Living systems store, retrieve, transmit and respond to information essential to life processes. Enduring understanding 3.A. Heritable information provides for continuity of life. Chapter/Key Concepts 3.A.1. DNA, and in some cases RNA, is the primary source of heritable information. 3.5, 10.3, 13.1, 13.2, 14.1, 14.2, 14.3, 14.5, 15.1, 15.2, 15.3, 15.4, 15.5, 16.1, 16.2, 16.3, 17.1, 17.3, 21.1, 21.2, 22.4 3.A.2. In eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization. 3.A.3. The chromosomal basis of inheritance provides an understanding of the pattern of passage (transmission) of genes from parent to offspring. 10.1, 10.2, 10.3, 11.1, 11.2, 13.1 11.2, 12.1, 12.2, 13.1, 14.2, 17.1, 17.4 3.A.4. The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. 4.3, 12.2, 13.1 Enduring understanding 3.B. Expression of genetic information involves cellular and molecular mechanisms. Chapter/Key Concepts 3.B.1. Gene regulation results in differential gene expression, leading to cell specialization. 7.3, 7.6, 16.1, 16.2, 16.3, 16.4, 16.5, 17.3 3.B.2. A variety of intercellular and intracellular signal transmissions mediate gene expression. 9.1, 9.2, 9.3, 15.3, 17.1 Enduring understanding 3.C. The processing of genetic information is imperfect and is a source of genetic variation. Chapter/Key Concepts 3.C.1. Changes in genotype can result in changes in phenotype. 5.3, 11.2, 13.1,

13.2, 14.6, 15.1, 17.1, 18.1, 19.1, 19.3 3.C.2. Biological systems have multiple processes that increase genetic variation. 11.2, 13.1, 14.1, 14.6, 15.2, 17.1, 20.3, 21.2, 22.4 3.C.3. Viral replication results in genetic variation, and viral infection can introduce genetic variation into the hosts. 21.1, 21.2 Enduring understanding 3.D. Cells communicate by generating, transmitting and receiving chemical signals Chapter/Key Concepts 3.D.1. Cell communication processes share common features that reflect a shared evolutionary history. 4.6, 9.1, 9.2, 9.3, 9.4, 10.4, 37.2, 37.3 3.D.2. Cells communicate with each other through direct contact with other cells or from a distance via chemical signaling. 9.1, 9.3 3.D.3. Signal transduction pathways link signal reception with cellular response. 9.1, 9.2 3.D.4. Changes in signal transduction pathways can alter cellular response. 9.2, 9.3, 9.4 This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Preface 7 Big Idea 3: Living systems store, retrieve, transmit and respond to information essential to life processes. Enduring understanding 3.E. Transmission of information results in changes within and between biological systems. 3.E.1. Individuals can act on information and communicate it to others. 3.E.2. Animals have nervous systems that detect external and internal signals, transmit and integrate information, and produce responses. Chapter/Key Concepts 9.2, 9.4, 21.2, 36.1, 36.2, 36.3, 36.4, 36.5 6.1, 35.1, 35.2, 35.3, 35.4 Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties. Enduring understanding 4.A Interactions within biological systems lead to complex properties. Chapter/Key Concepts 4.A.1. The subcomponents of biological molecules and their sequence determine the properties of that molecule. 3.1, 3.2, 3.3, 3.4,

3.5, 5.2, 6.2, 14.1, 14.3, 14.4, 17.1 4.A.2. The structure and function of subcellular components, and their interactions, provide essential cellular processes. 3.4, 4.3, 4.4, 4.6, 10.3, 15.3 4.A.3. Interactions between external stimuli and regulated gene expression result in specialization of cells, tissues and organs. 16.1, 22.3, 43.6, 43.7 4.A.4. Organisms exhibit complex properties due to interactions between their constituent parts. 15.2, 17.1, 18.1, 22.3, 22.5, 30.5, 33.3, 34.3 4.A.5. Communities are composed of populations of organisms that interact in complex ways. 22.5, 23.5, 45.5, 45.6 4.A.6. Interactions among living systems and with their environment result in the movement of matter and energy. Enduring understanding 4.B Competition and cooperation are important aspects of biological systems. 3.2, 3.3, 6.2, 6.3, 6.6, 7.5, 7.6, 8.2, 10.3, 18.1, 23.1, 22.4, 45.2, 45.6, 46.2, 47.3 Chapter/Key Concepts 4.B.1. Interactions between molecules affect their structure and function. 3.5, 5.2, 6.2, 6.5, 8.3 4.B.2. Cooperative interactions within organisms promote efficiency in the use of energy and matter. 4.3, 7.3, 7.6, 45.6 4.B.3. Interactions between and within populations influence patterns of species distribution and abundance. 45.4, 45.6 4.B.4. Distribution of local and global ecosystems changes over time. 22.4, 23.1, 46.1, 47.1, 47.3 Enduring understanding 4.C. Naturally occurring diversity among and between components within biological systems affects interactions with the environment. Chapter/Key Concepts 4.C.1. Variation in molecular units provides cells with a wider range of functions. 3.4, 9.2, 10.3, 13.1, 15.5, 42.2, 49.

1 4.C.2. Environmental factors influence the expression of the genotype in an organism. 14.2, 19.3, 22.3, 30.4, 43.1 4.C.3. The level of variation in a population affects population dynamics. 7.5, 7.6, 19.1, 45.6, 47.1 8 Preface Big Idea 4: Biological systems interact, and these systems and their interactions possess complex properties. 4.C.4. The diversity of species within an ecosystem may influence the stability of the ecosystem. 45.6, 46.1 This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 9 1 | THE STUDY OF LIFE Figure 1.1 This NASA image is a composite of several satellite-based views of Earth. To make the whole-Earth image, NASA scientists combine observations of different parts of the planet. (credit: NASA/GSFC/NOAA/USGS) Chapter Outline 1.1: The Science of Biology 1.2: Themes and Concepts of Biology Introduction Viewed from space, Earth offers no clues about the diversity of life it harbors. The first forms of life on Earth are thought be microorganisms that existed for billions of years in the ocean before plants and animals appeared. The mammals, birds, and flowers that we see in modern times are mostly “recent” species, originating 130 to 200 million years ago. In fact, only in the last 200,000 years have humans started looking like we do today. Organisms evolve in response to each other. One of the best examples is disease causing organisms, which have to adapt to overcome the defenses of the organisms they infect. One such organism that has evolved to specialize in infection in humans is Plasmodium, the organism that causes malaria. Biologists use the process of science to learn about the world and the organisms living in it. For example, people have suspected for quite some time that people with blood type O are less likely to die from severe malaria. Now, a team of scientists have been able to explain why. By examining data from several experiments, and by using both inductive and deductive reasoning, the scientists concluded that A and B type blood reacts with a protein excreted by Plasmodium. This reaction causes severe illness. However, type O blood does not react with the protein. You can read more

(http://openstaxcollege.org/l/32plasmodium) about the response of type A and B blood groups to infection by Plasmodium. 1.1 | The Science of Biology In this section, you will explore the following questions: • What are the characteristics shared by the natural sciences? • What are the steps of the scientific method? 10 Chapter 1 | The Study of Life Connection for AP® courses Biology is the science that studies living organisms and their interactions with one another and with their environment. The process of science attempts to describe and understand the nature of the universe by rational means. Science has many fields; those fields related to the physical world, including biology, are considered natural sciences. All of the natural sciences follow the laws of chemistry and physics. For example, when studying biology, you must remember living organisms obey the laws of thermodynamics while using free energy and matter from the environment to carry out life processes that are explored in later chapters, such as metabolism and reproduction. Two types of logical reasoning are used in science: inductive reasoning and deductive reasoning. Inductive reasoning uses particular results to produce general scientific principles. Deductive reasoning uses logical thinking to predict results by applying scientific principles or practices. The scientific method is a step-by-step process that consists of: making observations, defining a problem, posing hypotheses, testing these hypotheses by designing and conducting investigations, and drawing conclusions from data and results. Scientists then communicate their results to the scientific community. Scientific theories are subject to revision as new information is collected. The content presented in this section supports the Learning Objectives outlined in Big Idea 2 of the AP® Biology Curriculum Framework. The Learning Objectives merge Essential Knowledge content with one or more of the seven Science Practices. These objectives provide a transparent foundation for the AP® Biology course, along with inquiry-based laboratory experiences, instructional activities, and AP® Exam questions. Big Idea 2 Enduring Understanding 2.A Essential Knowledge Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain dynamic homeostasis. Growth, reproduction and maintenance of living systems require free energy and matter. 2.A.1 All living systems require constant input of free energy. Science Practice 6.4 The student can make claims and predictions about natural phenomena based on scientific theories and models Learning Objectives 2.3 The student is able to predict how changes in free energy availability affect organisms, populations and ecosystems. (a) (b) Figure 1.2 Formerly called

blue-green algae, these (a) cyanobacteria, shown here at 300x magnification under a light microscope, are some of Earth’s oldest life forms. These (b) stromatolites along the shores of Lake Thetis in Western Australia are ancient structures formed by the layering of cyanobacteria in shallow waters. (credit a: modification of work by NASA; credit b: modification of work by Ruth Ellison; scale-bar data from Matt Russell) What is biology? In simple terms, biology is the study of living organisms and their interactions with one another and their environments. This is a very broad definition because the scope of biology is vast. Biologists may study anything from the microscopic or submicroscopic view of a cell to ecosystems and the whole living planet (Figure 1.2). Listening to the daily news, you will quickly realize how many aspects of biology are discussed every day. For example, recent news topics This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 11 include Escherichia coli (Figure 1.3) outbreaks in spinach and Salmonella contamination in peanut butter. On a global scale, many researchers are committed to finding ways to protect the planet, solve environmental issues, and reduce the effects of climate change. All of these diverse endeavors are related to different facets of the discipline of biology. Figure 1.3 Escherichia coli (E. coli) bacteria, seen in this scanning electron micrograph, are normal residents of our digestive tracts that aid in the absorption of vitamin K and other nutrients. However, virulent strains are sometimes responsible for disease outbreaks. (credit: Eric Erbe, digital colorization by Christopher Pooley, both of USDA, ARS, EMU) The Process of Science Biology is a science, but what exactly is science? What does the study of biology share with other scientific disciplines? Science (from the Latin scientia, meaning “knowledge”) can be defined as knowledge that covers general truths or the operation of general laws, especially when acquired and tested by the scientific method. It becomes clear from this definition that the application of the scientific method plays a major role in science. The scientific method is a method of research with defined steps that include experiments and careful observation. The steps of the scientific method will be examined in detail later, but one of the most important aspects of this method is the testing of

hypotheses by means of repeatable experiments. A hypothesis is a suggested explanation for an event, which can be tested. Although using the scientific method is inherent to science, it is inadequate in determining what science is. This is because it is relatively easy to apply the scientific method to disciplines such as physics and chemistry, but when it comes to disciplines like archaeology, psychology, and geology, the scientific method becomes less applicable as it becomes more difficult to repeat experiments. These areas of study are still sciences, however. Consider archaeology—even though one cannot perform repeatable experiments, hypotheses may still be supported. For instance, an archaeologist can hypothesize that an ancient culture existed based on finding a piece of pottery. Further hypotheses could be made about various characteristics of this culture, and these hypotheses may be found to be correct or false through continued support or contradictions from other findings. A hypothesis may become a verified theory. A theory is a tested and confirmed explanation for observations or phenomena. Science may be better defined as fields of study that attempt to comprehend the nature of the universe. Natural Sciences What would you expect to see in a museum of natural sciences? Frogs? Plants? Dinosaur skeletons? Exhibits about how the brain functions? A planetarium? Gems and minerals? Or, maybe all of the above? Science includes such diverse fields as astronomy, biology, computer sciences, geology, logic, physics, chemistry, and mathematics (Figure 1.4). However, those fields of science related to the physical world and its phenomena and processes are considered natural sciences. Thus, a museum of natural sciences might contain any of the items listed above. 12 Chapter 1 | The Study of Life Figure 1.4 The diversity of scientific fields includes astronomy, biology, computer science, geology, logic, physics, chemistry, mathematics, and many other fields. (credit: “Image Editor”/Flickr) There is no complete agreement when it comes to defining what the natural sciences include, however. For some experts, the natural sciences are astronomy, biology, chemistry, earth science, and physics. Other scholars choose to divide natural sciences into life sciences, which study living things and include biology, and physical sciences, which study nonliving matter and include astronomy, geology, physics, and chemistry. Some disciplines such as biophysics and biochemistry build on both life and physical sciences and are interdisciplinary. Natural sciences are sometimes referred to as “hard science” because they rely on the use of quantitative data; social sciences that

study society and human behavior are more likely to use qualitative assessments to drive investigations and findings. Not surprisingly, the natural science of biology has many branches or subdisciplines. Cell biologists study cell structure and function, while biologists who study anatomy investigate the structure of an entire organism. Those biologists studying physiology, however, focus on the internal functioning of an organism. Some areas of biology focus on only particular types of living things. For example, botanists explore plants, while zoologists specialize in animals. Scientific Reasoning One thing is common to all forms of science: an ultimate goal “to know.” Curiosity and inquiry are the driving forces for the development of science. Scientists seek to understand the world and the way it operates. To do this, they use two methods of logical thinking: inductive reasoning and deductive reasoning. Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. This type of reasoning is common in descriptive science. A life scientist such as a biologist makes observations and records them. These data can be qualitative or quantitative, and the raw data can be supplemented with drawings, pictures, photos, or videos. From many observations, the scientist can infer conclusions (inductions) based on evidence. Inductive reasoning involves formulating generalizations inferred from careful observation and the analysis of a large amount of data. Brain studies provide an example. In this type of research, many live brains are observed while people are doing a specific activity, such as viewing images of food. The part of the brain that “lights up” during this activity is then predicted to be the part controlling the response to the selected stimulus, in this case, images of food. The “lighting up” of the various areas of the brain is caused by excess absorption of radioactive sugar derivatives by active areas of the brain. The resultant increase in radioactivity is observed by a scanner. Then, researchers can stimulate that part of the brain to see if similar responses result. Deductive reasoning or deduction is the type of logic used in hypothesis-based science. In deductive reason, the pattern of thinking moves in the opposite direction as compared to inductive reasoning. Deductive reasoning is a form of logical This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 13 thinking that uses a general principle or law to forecast specific results. From those general principles, a scientist can extrapolate and predict

the specific results that would be valid as long as the general principles are valid. Studies in climate change can illustrate this type of reasoning. For example, scientists may predict that if the climate becomes warmer in a particular region, then the distribution of plants and animals should change. These predictions have been made and tested, and many such changes have been found, such as the modification of arable areas for agriculture, with change based on temperature averages. Both types of logical thinking are related to the two main pathways of scientific study: descriptive science and hypothesisbased science. Descriptive (or discovery) science, which is usually inductive, aims to observe, explore, and discover, while hypothesis-based science, which is usually deductive, begins with a specific question or problem and a potential answer or solution that can be tested. The boundary between these two forms of study is often blurred, and most scientific endeavors combine both approaches. The fuzzy boundary becomes apparent when thinking about how easily observation can lead to specific questions. For example, a gentleman in the 1940s observed that the burr seeds that stuck to his clothes and his dog’s fur had a tiny hook structure. On closer inspection, he discovered that the burrs’ gripping device was more reliable than a zipper. He eventually developed a company and produced the hook-and-loop fastener often used on lace-less sneakers and athletic braces. Descriptive science and hypothesis-based science are in continuous dialogue. The Scientific Method Biologists study the living world by posing questions about it and seeking science-based responses. This approach is common to other sciences as well and is often referred to as the scientific method. The scientific method was used even in ancient times, but it was first documented by England’s Sir Francis Bacon (1561–1626) (Figure 1.5), who set up inductive methods for scientific inquiry. The scientific method is not exclusively used by biologists but can be applied to almost all fields of study as a logical, rational problem-solving method. Figure 1.5 Sir Francis Bacon (1561–1626) is credited with being the first to define the scientific method. (credit: Paul van Somer) The scientific process typically starts with an observation (often a problem to be solved) that leads to a question. Let’s think about a simple problem that starts with an observation and apply the scientific method to solve the problem. One Monday morning, a student arrives at class and quickly discovers that the classroom is too warm.

That is an observation that also describes a problem: the classroom is too warm. The student then asks a question: “Why is the classroom so warm?” Proposing a Hypothesis Recall that a hypothesis is a suggested explanation that can be tested. To solve a problem, several hypotheses may be proposed. For example, one hypothesis might be, “The classroom is warm because no one turned on the air conditioning.” But there could be other responses to the question, and therefore other hypotheses may be proposed. A second hypothesis might be, “The classroom is warm because there is a power failure, and so the air conditioning doesn’t work.” 14 Chapter 1 | The Study of Life Once a hypothesis has been selected, the student can make a prediction. A prediction is similar to a hypothesis but it typically has the format “If... then....” For example, the prediction for the first hypothesis might be, “If the student turns on the air conditioning, then the classroom will no longer be too warm.” Testing a Hypothesis A valid hypothesis must be testable. It should also be falsifiable, meaning that it can be disproven by experimental results. Importantly, science does not claim to “prove” anything because scientific understandings are always subject to modification with further information. This step—openness to disproving ideas—is what distinguishes sciences from nonsciences. The presence of the supernatural, for instance, is neither testable nor falsifiable. To test a hypothesis, a researcher will conduct one or more experiments designed to eliminate one or more of the hypotheses. Each experiment will have one or more variables and one or more controls. A variable is any part of the experiment that can vary or change during the experiment. The control group contains every feature of the experimental group except it is not given the manipulation that is hypothesized about. Therefore, if the results of the experimental group differ from the control group, the difference must be due to the hypothesized manipulation, rather than some outside factor. Look for the variables and controls in the examples that follow. To test the first hypothesis, the student would find out if the air conditioning is on. If the air conditioning is turned on but does not work, there should be another reason, and this hypothesis should be rejected. To test the second hypothesis, the student could check if the lights in the classroom are functional. If so, there is no power failure and this hypothesis should be

rejected. Each hypothesis should be tested by carrying out appropriate experiments. Be aware that rejecting one hypothesis does not determine whether or not the other hypotheses can be accepted; it simply eliminates one hypothesis that is not valid (see this figure). Using the scientific method, the hypotheses that are inconsistent with experimental data are rejected. While this “warm classroom” example is based on observational results, other hypotheses and experiments might have clearer controls. For instance, a student might attend class on Monday and realize she had difficulty concentrating on the lecture. One observation to explain this occurrence might be, “When I eat breakfast before class, I am better able to pay attention.” The student could then design an experiment with a control to test this hypothesis. In hypothesis-based science, specific results are predicted from a general premise. This type of reasoning is called deductive reasoning: deduction proceeds from the general to the particular. But the reverse of the process is also possible: sometimes, scientists reach a general conclusion from a number of specific observations. This type of reasoning is called inductive reasoning, and it proceeds from the particular to the general. Inductive and deductive reasoning are often used in tandem to advance scientific knowledge (see this figure) Think About It Almost all plants use water, carbon dioxide, and energy from the sun to make sugars. Think about what would happen to plants that don’t have sunlight as an energy source or sufficient water. What would happen to organisms that depend on those plants for their own survival? Make a prediction about what would happen to the organisms living in a rain forest if 50% of its trees were destroyed. How would you test your prediction? This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 15 Figure 1.6 The scientific method consists of a series of well-defined steps. If a hypothesis is not supported by experimental data, a new hypothesis can be proposed. In the example below, the scientific method is used to solve an everyday problem. Order the scientific method steps (numbered items) with the process of solving the everyday problem (lettered items). Based on the results of the experiment, is the hypothesis correct? If it is incorrect, propose some alternative hypotheses. Scientific Method 1 Observation 2 Question A B Everyday process There is something wrong with the electrical outlet. If something is wrong with the outlet, my coffeemaker also won’t work when plugged into it. 3

Hypothesis (answer) C My toaster doesn’t toast my bread. 4 5 Prediction D I plug my coffee maker into the outlet. Experiment E My coffeemaker works. 16 Chapter 1 | The Study of Life Scientific Method Everyday process 6 Result F What is preventing my toaster from working? a. The original hypothesis is correct. There is something wrong with the electrical outlet and therefore the toaster doesn’t work. b. The original hypothesis is incorrect. Alternative hypothesis includes that toaster wasn’t turned on. c. The original hypothesis is correct. The coffee maker and the toaster do not work when plugged into the outlet. d. The original hypothesis is incorrect. Alternative hypotheses includes that both coffee maker and toaster were broken. This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 17 Figure 1.7 Scientists use two types of reasoning, inductive and deductive reasoning, to advance scientific knowledge. As is the case in this example, the conclusion from inductive reasoning can often become the premise for deductive reasoning. Decide if each of the following is an example of inductive or deductive reasoning. 1. All flying birds and insects have wings. Birds and insects flap their wings as they move through the air. Therefore, wings enable flight. 2. Insects generally survive mild winters better than harsh ones. Therefore, insect pests will become more problematic if global temperatures increase. 3. Chromosomes, the carriers of DNA, separate into daughter cells during cell division. Therefore, DNA is the genetic material. 4. Animals as diverse as insects and wolves all exhibit social behavior. Therefore, social behavior must have an evolutionary advantage for humans. a. 1- Inductive, 2- Deductive, 3- Deductive, 4- Inductive b. 1- Deductive, 2- Inductive, 3- Deductive, 4- Inductive c. 1- Inductive, 2- Deductive, 3- Inductive, 4- Deductive d. 1- Inductive, 2-Inductive, 3- Inductive, 4- Deductive The scientific method may seem too rigid and structured. It is important to keep in mind that, although scientists often follow this sequence, there is flexibility. Sometimes an experiment leads to conclusions that favor a change in approach; often, an experiment brings entirely new scientific questions to the puzzle. Many times, science does not operate

in a linear fashion; instead, scientists continually draw inferences and make generalizations, finding patterns as their research proceeds. Scientific reasoning is more complex than the scientific method alone suggests. Notice, too, that the scientific method can be applied to solving problems that aren’t necessarily scientific in nature. 18 Chapter 1 | The Study of Life Two Types of Science: Basic Science and Applied Science The scientific community has been debating for the last few decades about the value of different types of science. Is it valuable to pursue science for the sake of simply gaining knowledge, or does scientific knowledge only have worth if we can apply it to solving a specific problem or to bettering our lives? This question focuses on the differences between two types of science: basic science and applied science. Basic science or “pure” science seeks to expand knowledge regardless of the short-term application of that knowledge. It is not focused on developing a product or a service of immediate public or commercial value. The immediate goal of basic science is knowledge for knowledge’s sake, though this does not mean that, in the end, it may not result in a practical application. In contrast, applied science or “technology,” aims to use science to solve real-world problems, making it possible, for example, to improve a crop yield, find a cure for a particular disease, or save animals threatened by a natural disaster (Figure 1.8). In applied science, the problem is usually defined for the researcher. Figure 1.8 After Hurricane Ike struck the Gulf Coast in 2008, the U.S. Fish and Wildlife Service rescued this brown pelican. Thanks to applied science, scientists knew how to rehabilitate the bird. (credit: FEMA) Some individuals may perceive applied science as “useful” and basic science as “useless.” A question these people might pose to a scientist advocating knowledge acquisition would be, “What for?” A careful look at the history of science, however, reveals that basic knowledge has resulted in many remarkable applications of great value. Many scientists think that a basic understanding of science is necessary before an application is developed; therefore, applied science relies on the results generated through basic science. Other scientists think that it is time to move on from basic science and instead to find solutions to actual problems. Both approaches are valid. It is true that there are problems that demand immediate attention; however, few solutions would be found without the help of the wide knowledge foundation generated through basic science. One

example of how basic and applied science can work together to solve practical problems occurred after the discovery of DNA structure led to an understanding of the molecular mechanisms governing DNA replication. Strands of DNA, unique in every human, are found in our cells, where they provide the instructions necessary for life. During DNA replication, DNA makes new copies of itself, shortly before a cell divides. Understanding the mechanisms of DNA replication enabled scientists to develop laboratory techniques that are now used to identify genetic diseases. Without basic science, it is unlikely that applied science would exist. Another example of the link between basic and applied research is the Human Genome Project, a study in which each human chromosome was analyzed and mapped to determine the precise sequence of DNA subunits and the exact location of each gene. (The gene is the basic unit of heredity; an individual’s complete collection of genes is his or her genome.) Other less complex organisms have also been studied as part of this project in order to gain a better understanding of human chromosomes. The Human Genome Project (Figure 1.9) relied on basic research carried out with simple organisms and, later, with the human genome. An important end goal eventually became using the data for applied research, seeking cures and early diagnoses for genetically related diseases. This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 19 Figure 1.9 The Human Genome Project was a 13-year collaborative effort among researchers working in several different fields of science. The project, which sequenced the entire human genome, was completed in 2003. (credit: the U.S. Department of Energy Genome Programs (http://genomics.energy.gov)) While research efforts in both basic science and applied science are usually carefully planned, it is important to note that some discoveries are made by serendipity, that is, by means of a fortunate accident or a lucky surprise. Penicillin was discovered when biologist Alexander Fleming accidentally left a petri dish of Staphylococcus bacteria open. An unwanted mold grew on the dish, killing the bacteria. The mold turned out to be Penicillium, and a new antibiotic was discovered. Even in the highly organized world of science, luck—when combined with an observant, curious mind—can lead to unexpected breakthroughs. Reporting Scientific Work Whether scientific research is basic science or applied science, scientists must share their findings in order for other researchers to expand and

build upon their discoveries. Collaboration with other scientists—when planning, conducting, and analyzing results—are all important for scientific research. For this reason, important aspects of a scientist’s work are communicating with peers and disseminating results to peers. Scientists can share results by presenting them at a scientific meeting or conference, but this approach can reach only the select few who are present. Instead, most scientists present their results in peer-reviewed manuscripts that are published in scientific journals. Peer-reviewed manuscripts are scientific papers that are reviewed by a scientist’s colleagues, or peers. These colleagues are qualified individuals, often experts in the same research area, who judge whether or not the scientist’s work is suitable for publication. The process of peer review helps to ensure that the research described in a scientific paper or grant proposal is original, significant, logical, and thorough. Grant proposals, which are requests for research funding, are also subject to peer review. Scientists publish their work so other scientists can reproduce their experiments under similar or different conditions to expand on the findings. The experimental results must be consistent with the findings of other scientists. A scientific paper is very different from creative writing. Although creativity is required to design experiments, there are fixed guidelines when it comes to presenting scientific results. First, scientific writing must be brief, concise, and accurate. A scientific paper needs to be succinct but detailed enough to allow peers to reproduce the experiments. The scientific paper consists of several specific sections—introduction, materials and methods, results, and discussion. This structure is sometimes called the “IMRaD” format. There are usually acknowledgment and reference sections as well as an abstract (a concise summary) at the beginning of the paper. There might be additional sections depending on the type of paper and the journal where it will be published; for example, some review papers require an outline. The introduction starts with brief, but broad, background information about what is known in the field. A good introduction also gives the rationale of the work; it justifies the work carried out and also briefly mentions the end of the paper, where the hypothesis or research question driving the research will be presented. The introduction refers to the published scientific work of others and therefore requires citations following the style of the journal. Using the work or ideas of others without proper citation is considered plagiarism. The materials and methods section includes a complete and accurate description of the substances used, and the method 20 Chapter 1 | The Study of Life and techniques used by the researchers to

gather data. The description should be thorough enough to allow another researcher to repeat the experiment and obtain similar results, but it does not have to be verbose. This section will also include information on how measurements were made and what types of calculations and statistical analyses were used to examine raw data. Although the materials and methods section gives an accurate description of the experiments, it does not discuss them. Some journals require a results section followed by a discussion section, but it is more common to combine both. If the journal does not allow the combination of both sections, the results section simply narrates the findings without any further interpretation. The results are presented by means of tables or graphs, but no duplicate information should be presented. In the discussion section, the researcher will interpret the results, describe how variables may be related, and attempt to explain the observations. It is indispensable to conduct an extensive literature search to put the results in the context of previously published scientific research. Therefore, proper citations are included in this section as well. Finally, the conclusion section summarizes the importance of the experimental findings. While the scientific paper almost certainly answered one or more scientific questions that were stated, any good research should lead to more questions. Therefore, a well-done scientific paper leaves doors open for the researcher and others to continue and expand on the findings. Review articles do not follow the IMRAD format because they do not present original scientific findings, or primary literature; instead, they summarize and comment on findings that were published as primary literature and typically include extensive reference sections. 1.2 | Themes and Concepts of Biology By the end of this section, you will be able to: • Identify and describe the properties of life • Describe the levels of organization among living things • Recognize and interpret a phylogenetic tree Connection for AP® Courses The AP® Biology curriculum is organized around four major themes called the Big Ideas that apply to all levels of biological organization—from molecules and cells to populations and ecosystems. Each Big Idea identifies key concepts called Enduring Understandings, and Essential Knowledges, along with supporting examples. Simple descriptions define the focus of each Big Idea: Big Idea 1, Evolution; Big Idea 2, Energy and Homeostasis; Big Idea 3, Information and Communication; and Big Idea 4, Systems and Interactions. Evolution explains both the unity and diversity of life, Big Idea 1, and all organisms require energy and molecules to carry out life functions, such as growth and reproduction, Big Idea 2. Living systems also store, transmit, and

respond to information, from DNA sequences to nerve impulses and behaviors, Big Idea 3. All biological systems interact, and these interactions result in emergent properties and characteristics unique to life, Big Idea 4. The redesigned AP® Biology course also emphasizes the investigative practices that students should master. Scientific inquiry usually uses a series of steps to gain new knowledge. The scientific method begins with an observation and follows with a hypothesis to explain the observation; then experiments are conducted to test the hypothesis, gather results, and draw conclusions from data. The AP® program has identified seven major categories of Science Practices, which can be described by short phrases: using representations and models to communicate information and solve problems; using mathematics appropriately; engaging in questioning; planning and implementing data collection strategies; analyzing and evaluating data; justifying scientific explanations; and connecting concepts. A Learning Objective merges content with one or more of the seven Science Practices. The information presented and the examples highlighted in this section support concepts and Learning Objectives outlined in Big Idea 1 of the AP® Biology Curriculum. The Learning Objectives listed in the Curriculum Framework provide a transparent foundation for the AP® Biology course, an inquiry-based laboratory experience, instructional activities, and AP® Exam questions. A Learning Objective merges required content with one or more of the seven Science Practices. This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 21 Big Idea 1 The process of evolution drives the diversity and unity of life. Enduring Understanding 1.B Organisms are linked by lines of descent from common ancestry. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice Learning Objective 3.1 The student can pose scientific questions. 1.14 The student is able to pose scientific questions that correctly identify essential properties of share, core life processes that provide insights into the history of life on Earth. Essential Knowledge 1.B.1 Organisms share many conserved core processes and features that evolved and are widely distributed among organisms today. Science Practice Learning Objective 5.3 The student can evaluate the evidence provided by data sets in relation to a particular scientific question. 1.18 The student is able to evaluate evidence provided by a data set in conjunction with a phylogenetic tree or simply cladogram to determine evolutionary history and speciation. Biology is the science that studies life, but what exactly is life? This may sound like

a silly question with an obvious response, but it is not always easy to define life. For example, a branch of biology called virology studies viruses, which exhibit some of the characteristics of living entities but lack others. It turns out that although viruses can attack living organisms, cause diseases, and even reproduce, they do not meet the criteria that biologists use to define life. Consequently, virologists are not biologists, strictly speaking. Similarly, some biologists study the early molecular evolution that gave rise to life; since the events that preceded life are not biological events, these scientists are also excluded from biology in the strict sense of the term. From its earliest beginnings, biology has wrestled with three questions: What are the shared properties that make something “alive”? And once we know something is alive, how do we find meaningful levels of organization in its structure? And, finally, when faced with the remarkable diversity of life, how do we organize the different kinds of organisms so that we can better understand them? As new organisms are discovered every day, biologists continue to seek answers to these and other questions. Properties of Life All living organisms share several key characteristics or functions: order, sensitivity or response to the environment, reproduction, adaptation, growth and development, regulation, homeostasis, energy processing, and evolution. When viewed together, these nine characteristics serve to define life. Order Figure 1.10 A toad represents a highly organized structure consisting of cells, tissues, organs, and organ systems. (credit: “Ivengo”/Wikimedia Commons) 22 Chapter 1 | The Study of Life Organisms are highly organized, coordinated structures that consist of one or more cells. Even very simple, single-celled organisms are remarkably complex: inside each cell, atoms make up molecules; these in turn make up cell organelles and other cellular inclusions. In multicellular organisms (Figure 1.10), similar cells form tissues. Tissues, in turn, collaborate to create organs (body structures with a distinct function). Organs work together to form organ systems. Sensitivity or Response to Stimuli Figure 1.11 The leaves of this sensitive plant (Mimosa pudica) will instantly droop and fold when touched. After a few minutes, the plant returns to normal. (credit: Alex Lomas) Organisms respond to diverse stimuli. For example, plants can bend toward a source of light, climb on fences and walls, or respond to touch (Figure 1.11).

Even tiny bacteria can move toward or away from chemicals (a process called chemotaxis) or light (phototaxis). Movement toward a stimulus is considered a positive response, while movement away from a stimulus is considered a negative response. Watch this video (http://openstaxcollege.org/l/movement_plants) to see how plants respond to a stimulus—from opening to light, to wrapping a tendril around a branch, to capturing prey. Which example most clearly shows a way that humans can respond directly to a change in the environment? a. We shiver when we are cold and sweat when we are hot. b. We walk by putting our front leg forward and pushing off with our back leg. c. We are able to breath in and out unconsciously. d. Our hair and fingernails grow at a constant rate over time. Reproduction Single-celled organisms reproduce by first duplicating their DNA, and then dividing it equally as the cell prepares to divide to form two new cells. Multicellular organisms often produce specialized reproductive germline cells that will form new individuals. When reproduction occurs, genes containing DNA are passed along to an organism’s offspring. These genes ensure that the offspring will belong to the same species and will have similar characteristics, such as size and shape. Growth and Development Organisms grow and develop following specific instructions coded for by their genes. These genes provide instructions that This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 23 will direct cellular growth and development, ensuring that a species’ young (Figure 1.12) will grow up to exhibit many of the same characteristics as its parents. Figure 1.12 Although no two look alike, these kittens have inherited genes from both parents and share many of the same characteristics. (credit: Rocky Mountain Feline Rescue) Regulation Even the smallest organisms are complex and require multiple regulatory mechanisms to coordinate internal functions, respond to stimuli, and cope with environmental stresses. Two examples of internal functions regulated in an organism are nutrient transport and blood flow. Organs (groups of tissues working together) perform specific functions, such as carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body. Homeostasis Figure 1.13 Polar bears (Ursus maritimus) and other mammals living in ice-covered regions maintain their body temperature by generating heat and reducing heat loss through thick fur

and a dense layer of fat under their skin. (credit: “longhorndave”/Flickr) In order to function properly, cells need to have appropriate conditions such as proper temperature, pH, and appropriate concentration of diverse chemicals. These conditions may, however, change from one moment to the next. Organisms are able to maintain internal conditions within a narrow range almost constantly, despite environmental changes, through homeostasis (literally, “steady state”). For example, an organism needs to regulate body temperature through a process known as thermoregulation. Organisms that live in cold climates, such as the polar bear (Figure 1.13), have body structures that help them withstand low temperatures and conserve body heat. Structures that aid in this type of insulation include fur, feathers, blubber, and fat. In hot climates, organisms have methods (such as perspiration in humans or panting in dogs) that help them to shed excess body heat. 24 Chapter 1 | The Study of Life Energy Processing Figure 1.14 The California condor (Gymnogyps californianus) uses chemical energy derived from food to power flight. California condors are an endangered species; this bird has a wing tag that helps biologists identify the individual. (credit: Pacific Southwest Region U.S. Fish and Wildlife Service) All organisms use a source of energy for their metabolic activities. Some organisms capture energy from the sun and convert it into chemical energy in food; others use chemical energy in molecules they take in as food (Figure 1.14). Activity Select an ecosystem of your choice, such as a tropical rainforest, desert, or coral reef, and create a representation to show how several organisms found in the ecosystem interact with each other and the environment. Then, using similarities and differences among the organisms make a hypothesis about their relatedness. Consider the levels of organization of the biological world and create a diagram to place these items in order from the smallest level of organization to the most encompassing: skin cell, planet Earth, elephant, tropical rainforest, water molecule, liver, wolf pack, and oxygen atom. Justify the reason why you placed the items in the hierarchy that you did. Think About It Homeostasis—the ability to “stay the same”—is a feature shared by all living organisms. You go for a long walk on a hot day. Describe how homeostasis keeps your body healthy even though you are sweating profusely. Then

describe an example of an adaptation that evolved in a desert plant or animal that allows them to survive in extreme temperatures. Levels of Organization of Living Things Living things are highly organized and structured, following a hierarchy that can be examined on a scale from small to large. The atom is the smallest and most fundamental unit of matter. It consists of a nucleus surrounded by electrons. Atoms form molecules. A molecule is a chemical structure consisting of at least two atoms held together by one or more chemical bonds. Many molecules that are biologically important are macromolecules, large molecules that are typically formed by polymerization (a polymer is a large molecule that is made by combining smaller units called monomers, which are simpler This OpenStax book is available for free at http://cnx.org/content/col12078/1.6 Chapter 1 | The Study of Life 25 than macromolecules). An example of a macromolecule is deoxyribonucleic acid (DNA) (Figure 1.15), which contains the instructions for the structure and functioning of all living organisms. Figure 1.15 All molecules, including this DNA molecule, are composed of atoms. (credit: “brian0918”/Wikimedia Commons) Watch this video (http://openstaxcollege.org/l/rotating_DNA) that animates the three-dimensional structure of the DNA molecule shown in this figure. The word helix means spiral. What does this tell you about the structure of DNA, which is a double helix macromolecule? a. The nucleotides of the two strands bond together with spiral bonds. b. A double-stranded DNA molecule has two spiral stands bound together. c. DNA is a double helix because it has two spiral strands held together like a spiral staircase. d. Nucleotides are spiral-shaped molecules that bond together to form DNA. 26 Chapter 1 | The Study of Life Some cells contain aggregates of macromolecules surrounded by membranes; these are called organelles. Organelles are small structures that exist within cells. Examples of organelles include mitochondria and chloroplasts, which carry out indispensable functions: mitochondria produce energy to power the cell, while chloroplasts enable green plants to utilize the energy in sunlight to make sugars. All living things are made of cells; the cell itself is the smallest fundamental unit of structure and function in living organisms. (This requirement is why viruses are not considered living: