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10 Biotechnology and its Application Topics Covered 1 0.1 Biotechnological Applications in Agriculture 1 0.2 Biotechnological Applications in Medicine 10.3 Transgenic Animals 10.4 Ethical Issues C hapter map BIOTECHNOLOGY AND ITS APPLICATION In Agriculture In Medicine Transgenic plants and Gene e.g., Pest resistance e.g., Genetically Animals Therapy crops of cotton & engineered insulin & • ADA Molecular diagnosis. • S tudy of disease, vaccine • SCID tobacco plants safety, biological product Patent • Novelty Ethical Issues • GM plants • Non-obviousness • Biosafety • Bt cotton • Utility • Biopiracy Biotechnology is used in various fields for human welfare by modifying organisms genetically. Topic 1. Biotechnological Applications in Agriculture • Crops which are modified by altering their genes are called genetically modified crops (GM crops). • The beneficial changes obtained in genetically modified crops are: There is increased level of tolerance for some abiotic stress factors such as cold, drought, salinity and high temperature Pesticide resistant crops have reduced dependence on pesticides and insecticides. Plants can use available nutrients more efficiently so soil remains fertile for longer time. Significant reduction in post harvest losses, shelf life increased. Nutritional value of a food crop is increased, e.g. vitamin–A enriched rice. It also provides alternative resource to industries by supplying starches, fuels and pharmaceuticals. Bt cotton: It is pest resistant cotton produced by inserting a gene from a bacterium Bacillus thuringiensis which produces insecticidal protein. • This protein kills some insects like Lepidopteron: cotton bollworm, tobacco budworm, armyworm Coleopterans: beetles 250

Dipterans: flies and mosquitoes • Genes which produce this type of protein are inserted in cotton plant. • Different genes target different type of insects cryIAc and cryIIAb is used to control cotton bollworms cryIAb is used to control corn borer Cotton boll: (a) Destroyed by bollworms, (b) A fully mature cotton boll Pest Resistant Plants • A nematode Meloidogyne incognita infects the roots of tobacco plants. The yield of the plant decreases drastically due to this. • To prevent the infection, the process called RNA interference (RNAi) is used. • RNAi is a natural cellular defense mechanism of all eukaryotic cells. The mRNA is silenced due to formation of dsRNA which binds to RNA and does not allow translation of RNA. • The source of complementary RNA could be a RNA virus, a transposen etc. • Using Agrobacterium vector, nematode specific genes were introduced in host plant. This produces both sense and anti-sense RNA in host cells. Being complementary, these two strands form dsRNA. • Upon infection by a nematode, this dsRNA initiates RNAi and silence mRNA of nematode which eventually leads to death of nematode. RNA Feeding tube dsRNA siRNA Plant nucleus RNA interference Topic 2. Biotechnological Applications in Medicine More than 30 therapeutic drugs have been produced and used by recombinant DNA technology. Out of which 12 are being marketed presently. Biotechnology and its Application  251

Genetically Engineered Insulin mass of preimplantation embryos. Another example is induced pluripotent stem cells (iPSCs) derived • Earlier insulin for diabetes was extracted from from the epiblast layer of implanted embryos. pancreas of slaughtered cattle and pigs. This caused Their pluripotency is a continuum, starting from allergy to many patients due to foreign proteins. completely pluripotent cells such as ESCs and iPSCs and ending or representatives with less potency– • Insulin is produced in human body in pro-hormone multi-, oligo- or unipotent cells. One of the methods (inactive) form and consists of three polypeptide to assess their activity and spectrum is the teratoma chains, A, B and C peptide. The C-peptide is removed formation assay. iPSCs are artificially generated during maturation of pro-insulin to insulin. from somatic cells, and they function similarly to PSCs. Their culturing and utilization are very • Eli Lilly Company of America in 1983 used promising from present and future regenerative recombinant technology to produce human insulin. medicine. • Human insulin genes were inserted in E. coli for • Multipotent stem cells have a narrower spectrum of polypeptide A and B separately. Chains A and B differentiation than PSCs, but they can specialize in were extracted and were combined by creating discrete cells of specific cell lineages. One example is disulphide bonds to form human insulin. a haematopoietic stem cells, which can develop into several types of blood cells. After differentiation, a Proinsulin A-peptide haematopoietic stem cell becomes and oligopotent s cell. Its differentiation abilities are then restricted to ss s cells of its lineage. However, some multipotent cells s are capable of conversion into unrelated cell types, s A peptide which suggests naming them pluripotent cells. s ss s Insulin • Oligopotent stem cells can differentiate into several cell types. A myeloid stem cells is an example that ss can divide into white blood cells but not red blood s cells. s • Unipotent stem cells are characterized by the + B peptide narrowest differentiation capabilities and a special property of dividing repeatedly. Their latter feature Free C-peptide makes them a promising candidate for therapeutic use in regenerative medicine. These cells are only Maturation of pro-insulin into insulin after removal able to form one cell type, e.g. dermatocytes. of C-peptide (simplified) Gene Therapy Stem Cell Technology • A person with inborn genetic defect can be corrected • Stem cells are unspecialized cells of the human body. by replacing defective gene with the correct one in They are able to differentiate into any cell of an the cell or tissue. This is called gene therapy and is organism and have the ability of self-renewal. Stem done to treat a disease. cells exist both in embryos and adult cells. There are several steps of specialization. Developmental • First clinical gene therapy was given in 1990 to potency is reduced with each step, which means that 4-year-old girl with adenosine deaminase (ADA) a unipotent stem cell is not able to differentiate into deficiency. ADA is responsible for immune system as many types of cells as a pluripotent one. to function. • Totipotent stem cells are able to divide and • Some children with ADA deficiency can be treated differentiate into cells of the whole organism. by bone marrow transplant. Totipotency has the highest differentiation potential and allows cells to form both embryo and extra- • Some others are treated by enzyme replacement embryonic structures. One example of a totipotent therapy, in which functional ADA is given to patient cell is a zygote, which is formed after a sperm by injection. fertilizes an egg. These cells can later develop either into any of the three germ layers or form a placenta. • Both these approaches are not permanent cure. After approximately 4 days, the blastocyst's inner cell mass becomes pluripotent. This structure is the • In gene therapy, the lymphocytes are cultured and source of pluripotent cells. functional ADA gene is inserted in lymphocytes by using a retrovirus. These cells are then again • Pluripotent stem cells (PSCs) form cells of all germ transferred into the body of patient. Cells not being layers but not extraembryonic structures, such immortal, patient needs repeated transfusion of as the placenta. Embryonic stem cells (ESCs) are such cells. an example. ESCs are derived from the inner cell 252 Biology–12

• Gene when replaced in early embryonic stage is a patients and mutations in suspected cancer permanent cure of ADA deficiency. patients. Detection of many genetic disorders also became possible due to PCR. Molecular Diagnosis • Presence of a disease or a pathogen is very helpful • A single stranded DNA or RNA with known sequence is tagged with radioactive molecule which acts as a to treat the patient timely. Earlier methods of probe → this is now hybridized to its complementary diagnosis were based on serum and urine analysis, DNA in clone of cells → the detection is then done for which early detection was not possible. using autoradiography → mutated gene will not appear on photographic film because probe will not • New techniques like PCR and ELISA (Enzyme be able to find its complementary strand. Linked Immune-sorbant Assay) are very effective tools for early diagnosis of a disease and results can • In ELISA, the pathogens are detected by the be obtained at very low concentration of pathogen presence of antigens like proteins, glycoproteins in body. etc. with antigen-antibody interaction or specific antibodies which are produced by the body. • PCR is used to detect HIV in suspected AIDS Topic 3. Transgenic Animals caused in humans, e.g. gene of human protein a-1-antitrypsin used to treat emphysema is • Animals manipulated with the foreign gene and inserted in transgenic animals. Similarly genes have ability to express it are transgenic animals. to treat phenylketonuria (PKU) and cystic fibrosis are also used. Human alpha-lactalbumin gene was • Reasons for producing transgenic animals: introduced and expressed in a cow Rosie in 1997. This cow produced milk enriched with human Normal physiology and development: Normal protein which is nutritionally more balanced for function and regulation of genes are studied, human consumption. e.g. genes involved in the formation, regulation and biological effects of complex growth factors Vaccine safety: Transgenic mice are developed such as insulin like growth factors are studied by to test the safety of vaccines before they are used introducing the genes in other species. on human beings such as polio vaccine was tested on transgenic mice. Study of disease: Animals are tailor made to study the contribution of genes in the development Chemical safety testing: Certain genes are of disease, e.g. Transgenic animals are used as introduced into animals which make them more models to study cancer, cystic fibrosis, rheumatoid sensitive to toxic substances. In such cases the arthritis and alzheimer’s. effects can be studied when animals are exposed to toxic substances. Biological products: Genes for some biological products are inserted and obtained from transgenic animals which help to treat some of the diseases Topic 4. Ethical Issues to inventor(s) or their assignee for a limited period of time in exchange for a public disclosure of an • In recent years, a regulation has been laid for invention. manipulation of living organisms. Ethical standards have been set up which evaluate the morality • Patents should fulfill three criteria: novelty, non- of human activities whether they are helping or obviousness and utility. harming any living organisms. Novelty: innovation must be new • If a genetically modified organism is introduced into Non-obviousness: it may not be documented but the environment, it may have unpredictable results. is otherwise well known. • Government of India has set up an organization, Genetic Engineering Approval Committee Utility: the discovery should be useful to human (GEAC) which makes decisions regarding the beings. validity of GM research and the safety of introducing GM organisms for the utility of human beings. Biopiracy: Illegal use of living organism or the products obtained by some multinational companies • Problems arise in patent grants due to utility or other organizations without paying or taking proper of living or GM organisms. Patent is a set of authorization from countries or people concerned. exclusive rights granted by a national government • The financially rich industrialized countries are not Biotechnology and its Application  253

bio-diverse countries. In contrast, underdeveloped four months of submissions it was established that countries are full of bio-resources and traditional the use of turmeric as a healing agent was well knowledge. Rich countries take advantage and use known in India for centuries and the patent was the products or knowledge of other countries without revoked. giving adequate compensation and share of benefit. • Neem: Similarly, in 1996, Vandana Shiva challenged • Indian government has amended Indian patent bill the patent granted to firm of W.R. Grace and that takes such issues into consideration, including Company by European patent office, Munich for the patent terms, emergency provisions and research fungicidal use of Neem oil. Vandana Shiva and Ajay and development initiative. Phadke, both researched on neem tree and proved by citing Indian vedic literature that the use of neem as Controversies in India Regarding Patent and a medicine does not fulfill the criteria of novelty. The Biopiracy legal action taken by government of India resulted in revoking of patent in 2005. • Turmeric: University of Mississippi Medical Centre patented the use of turmicin (product obtained from • Basmati rice: In September 1997, an American turmeric) in wound healing in May, 1995. That company Rice Tec. patent on “basmati rice line and meant if an Indian, due to its traditional knowledge grains” including ways of selecting rice for breeding. passed from generations, uses turmeric for healing a scrape, he would be implicated of breaking patent • The company was framed into biopiracy after India law and could be prosecuted for the same. threatened to take the matter to World Trade Organisation (WTO) as violation of trade related • The patent was challenged by Dr. R.A. Mashelkar, aspects of intellectual property rights (TRIPS). The an Indian scientist who has done much to awaken company finally lost the claim of patent. India to Intellectual Property Rights issues. After EXERCISE I. Multiple Choice Questions (c) Either RNA or DNA 1. Bt cotton is not: (a) A GM plant (d) Can be ssDNA but not ssRNA (b) Insect resistant (c) A bacterial gene expressing system 6. The site of production of ADA in the body is: (d) Resistant to all pesticides (a) Erythrocytes (b) Lymphocytes 2. C-peptide of human insulin is: (a) A part of mature insulin molecule (c) Blood plasma (d) Osteocytes (b) Responsible for formation of disulphide 7. The trigger for activation of toxin of Bacillus bridges thuringiensis is: (c) Removed during maturation of pro-insulin to (a) Acidic pH of stomach insulin (d) Responsible for its biological activity. (b) High temperature 3. GEAC stands for: (a) Genome Engineering Action Committee (c) Alkaline pH of gut (b) Ground Environment Action Committee (c) Genetic Engineering Approval Committee (d) Mechanical action in the insect gut (d) G e n e t i c a n d E n v i r o n m e n t A p p r o v a l 8. Golden rice is: Committee (a) A variety of rice grown along the yellow river 4. a -1 antitrypsin is: in China (a) An antacid (b) An enzyme (b) Long stored rice having yellow colour tint (c) Used to treat arthritis (d) Used to treat emphysema (c) A transgenic rice having gene for beta 5. A probe which is a molecule used to locate specific carotene sequences in a mixture of DNA or RNA molecules (d) Wild variety of rice with yellow coloured could be: grains (a) A single stranded RNA (b) A single stranded DNA 9. In RNAi, genes are silenced using: (a) ssDNA (b) dsDNA 254 Biology–12 (c) dsRNA (d) ssRNA 10. The first clinical gene therapy was done for the treatment of: (a) AIDS (b) Cancer (c) Cystic fibrosis (d) SCID (Severe Combined Immuno Deficiency resulting from deficiency of ADA)

11. ADA is an enzyme which is deficient in a genetic 7. What happens when Meloidogyne incognita disorder SCID. What is the full form of ADA? consumes cells with RNAi gene? [Delhi 2012] 8. Biotechnologists refer to Agrobacterium (a) Adenosine deoxyaminase tumefaciens as a natural genetic engineer of (b) Adenosine deaminase plants. Give reasons to support the statement. (c) Aspartate deaminase  [All India 2011] (d) Arginine deaminase 9. How does dsRNA gain entry into a eukaryotic cell to cause RNA interference? [Delhi 2011 C] II. Fill in the Blanks 10. Name the cry genes that control cotton bollworm 1. U.S. _____ does not recognize technologies and and corn borer respectively. [All India 2009 C] 11. How does silencing of specific mRNA in RNA methods used in other countries as ‘prior art’. interference prevent parasitic infestation? 2. Bacillus thuringiensis produces a ____, which  [Delhi 2008 C] 12. How are tobacco plants benefited when nematode kills insects. specific genes are introduced into them using 3. _____ grants farmers the right to save, use, sow certain vectors? Name the vectors used.  [Delhi 2008 C] and sell his farm products. 13. Suggest any two possible treatments that can 4. GMO stands for _____ be given to a patient exhibiting adenosine 5. A _____ is a piece of single stranded DNA which deaminsase deficiency. [All India 2015] is tagged with a radio active molecule. 14. State the role of C-peptide in human insulin.  [All India 2014] III. True or False 15. A boy has been diagnosed with ADA deficiency. 1. Insulin for curing diabetes should only come from Suggest any one possible treatment.  [Delhi 2014 C] animals. 16. How is proinsulin different from functional 2. Insulin has three peptide chain in prohorme insulin in humans? [All India 2012 C] 17. Name any two techniques that serve the purpose stage. of early diagnosis of some bacterial/viral disease. 3. ADA deficiency can lead to severe combined  [Foreign 2011] OR immuno deficiency. Name a molecular diagnostic technique to detect 4. In Bt cotton the gene responsible to make insect the presence of a pathogen in its early stage of resistance is cry. 5. B. thuringiensis bacterium which produces toxins are harmful for the bacteria. IV. M atch the items in Column I with those of Column II: Column I Column II infection. [Delhi 2010] 18. How two short polypeptide chains of insulin are (A) Polymerase chain (i) Steroid linked together? [Delhi 2009 C] reaction 19. Suggest any two techniques which can help in (B) Eli Lilly (ii) Biological control early detection of bacterial/viral infection much before the symptom appear in the body. (C) Insulin (iii) Humulin  [All India 2008] (D) Cholesterol (iv) Kary Mullis 20. Name the Indian variety of rice patented by an American company. [Delhi 2008] (E) IPM (v) Neomycin 21. A multinational company outside tried to sell (vi) Islets of new varieties of turmeric without proper patent Langerhens rights. What is such an act referred to?  [All India 2008] 1 Mark Questions 22. What was the specialty of the milk produced 1. Why do children cured by enzyme replacement by the transgenic cow Rosie? [All India 2008] therapy for adenosine deaminase deficiency need 23. Name the specific type of gene that is incorporated periodic treatment?  [All India 2015] in a cotton plant to protect the plant against cotton 2. What are transgenic animals? Give an example. boll worm infestation. [All India 2017] 3. What is Biopiracy?  [Delhi 2015, All India 2016] 24. Bt-toxins are released as inactive crystals in the 4. Mention two objectives of setting up GEAC by bacterial body. What happens to it in the cotton boll worm body that it kills the boll worm? our Government.  [All India 2016]  [All India 2017] 5. State the role of transposons in silencing of 25. Mention the chemical change that proinsulin mRNA in eukaryotic cells. [All India 2013] undergoes, to be able to act as mature insulin. 6. Write the possible source of RNA interference (RNAi) gene. [Delhi 2013 C]  [CBSE 2018] Biotechnology and its Application  255

2 Marks Questions 41. (a) Name the deficiency for which first clinical     23322332(a2016378 9)........ (NpcGEWHEWtcWccpW(aobohorrrxxiaoywd)w)hrhhooevpp wm1iedMadmaNDtyyea?tllAhafautuefreiaNfaEioeddeiiscdcdcecnntntmrnooexAeacsoh‘hgr?ReesthesptteleeeeeceiShssixosloctinnooidatsfttesahiwt‘rBBteuhnap,coii,maorbpneritnbiettaetlbye’eyrt.tpucc(cohhbv’nttuihtbiltAtogoosceateeeitti)enexxsoeokcDrctrocsRknniistentoiieecfnnsAoemildiesxNcldlaflrorosiliiOilnnopetdtiusfcAprfuuiahfr.otsooRenissRtsrehmeretittfuoeyenditNntesccaihkkdittdtunaihdAnnehieiieiccsfninllrsscnaoefdllcBiefeeesfdnrletecicettaeaclsystritsphhrttcsnceetseerrteteeiiihrapfnna nlnho[[ucfcsleetAAcednbboteualhehsehr[[lltuaasfsansAAtllubeiaturf(cccns.tontIIellRmootbttme.thllnngnrcmeed[[[[eesNSiuIIddDDDDaererramnynnccai.iishrniiAeeeenanaaorgdduuitllllpospnosrsishhhhegiinmm22.w)taarrp.ygsiiiiN00oieoAmi.tst22222211recwts?ttatD000000mnt54eahhemei111011iisdAtCCaamnadt211484ihee?stt-l]]]]]]]]./   4444444 6472583 ....... (DtMdeha(LwNopdlEaaWHWtbyahhfnnneeauixperaom))sheeertfetzd impsewmitAerirPitnyMgdayccparetaeacataericDemCtemehnintihpepenihisnfnosibRdoAtnioeyntyenaytn.esctscehrnt.htthngi.te?eytt edtheeirtpewoSMefeotchtehneatfeneahodnteifeohtaepcfesfnaimttriecruytocepnmsigettttacmieli.pneblerhtnealeupiniosoiaoricentencttroylntwettdstonaeeecnh.haesaei uccwti?tyoaeapntenaniu.cathSonnansspuWgttlhAOcneiuapscsasooaa[DaAreuDrrogARetngonnatuoiiDsNgnodlfitAepdfsslowvotefeidAneAyhie-fafIesmmabadtaenttgengp(haddl.ostecrdebuneea.renehpfefteni)nftooicaafpadpniccatAcsEhieorkatieioco2etttfsoenDioLirseuie0disetn[[[enctncmosdAAA1IsinAunhnatitltneSoe4blllorotgaeelclllnpeA.dlegdloecmCync[yIIIegeaDfhyuneufnnne,dep[[[t.oeptafneerdddrnDDDDihtehiranpeleeiiiiicthieeeeaeqetaaatrngapnnilllliihlcmmfeuhhhhinldgetp222o2unicen.eiiiinic000ira0iaAressnca2222gn111tg1neneeyDt0000tgae2114eanarehic1111fnnnoeAsnsCCCeCoiio3333innnddeeeesrrtt-]]]]]]]] example that these are encoded by different forms cure. [Delhi 2010] of the genes. [All India 2012] 49. How did Eli Lilly synthesise the human insulin? 34. How does ‘RNA interference’ takes place in Mention one difference between this insulin and eukaryotes? Mention its importance. the one produced by the human pancreas.  [Delhi 2012 C]  [All India 2010, Delhi 2010 C] 35. List any four advantages of genetically modified plants. 50. (a) List the three molecular diagnostic techniques [Delhi 2012 C, All India 2008 C] that help detect pathogens from suspected OR patients. Write any two ways how genetically modified (b) Mention the advantage of these techniques plants are found to be useful? [All India 2014 C] over conventional methods.  [Delhi 2009 C] OR Highlight any four advantages of Genetically 51. Expand ELISA. On what principle is ELISA test based? List two ways by which an infection can Modified Organisms (GMOs).  [Foreign 2009; All India 2008 C] be detected by this test. [All India 2009 C] 36. Explain the process of RNA interference. 52. State the principle on which ELISA technique is based. How does it help in early detection of a  [Delhi 2011] 37. How is Bt cotton made to attain resistance disease? [Delhi 2008 C] against bollworm? [Delhi 2010] 53. How is gene therapy being used in treating ADA 38. Nematode specific genes are introduced into deficiency patients? [All India 2008 C] the tobacco plants using Agrobacterium 54. (a) What is biopiracy? vectors to develop resistance in tobacco plants (b) State the initiative taken by the Indian against nematodes. Explain the events that occur parliament against it. [Delhi 2014] in tobacco plant to develop resistance.[Delhi2009] 55. Biopiracy should be prevented. State why and 39. What is gene therapy? Name the first clinical how? [All India 2011] case in which it was used. [Delhi 2014] 56. Human insulin when synthesised in the body 40. Why is proinsulin so called? How is insulin needs to be processed before it can act. Explain different from it? [All India 2014 C, 2013] giving reasons? [Delhi 2014 C] 256 Biology–12

57. (a) State the role of DNA ligase in biotechnology. OR (b) What happens when Meloidogyne incognita Explain the steps involved in the production of consumes cells with RNAi gene?[Delhi 2012] genetically engineered insulin. [All India 2008] 58. How have transgenic animals proved to be OR beneficial in: How did Eli Lilly company go about preparing the (a) Production of biological products. human insulin? How is the insulin thus produced, (b) Chemical safety testing. [All India 2014] different from that produced by the functional 59. Mention any four benefits derived from transgenic animals. [Delhi 2012 C] human insulin gene? [Foreign 2008] 60. Describe the responsibility of GEAC, set up by 67. Explain enzyme-replacement therapy to treat adenosine deaminase deficiency. Mention two the Indian Government. [Delhi 2009] disadvantages of this procedure.[All India 2016] 3 Marks Questions 68. Describe any three potential applications of genetically modified plants. 61. What is a GMO? List any five possible advantages of a GMO to a farmer.  [All India 2015 C, 2014 C] 69. How did the process of RNA interference help to 62. One of the major contributions of biotechnology control the nematode from infecting the roots of is to develop pest-resistant varieties of cotton plants. Explain how it has been made possible. tobacco plants? [Delhi 2014]  [Foreign 2015 (C)] 70. (a) How has biotechnology helped in producing Meloidogyne incognita resistant tobacco 63. Biotechnology has played an important role in plant? developing boll worm resistant cotton plants. Explain how such cotton plants are developed (b) Why does this nematode die on eating such a and made resistant to boll worm. [All India 2015] GM plant? [Delhi 2014 C, 2010 C] 71. Name the pest that destroys the cotton bolls. 64. (a) Tobacco plants are damaged severely when Explain the role of Bacillus thuringiensis in infested with Meloidogyne incognita. Name protecting the cotton crop against the pest to and explain the strategy that is adopted to stop this infestation. increase the yield. [All India 2013] 72. How is the Bt cotton plant created as a GM plant? (b) Name the vector used for introducing the How is it protected against bollworm infestation? nematode specific gene in tobacco plant.  [Delhi 2013 C]  [All India 2012] 73. Name the nematode that damages the roots of OR tobacco plants. How is transgenic tobacco plant N a m e t h e h o s t p l a n t a n d i t s p a r t t h a t made resistant to nematode using biotechnology? Meloidogyne incognita infects. Explain the role of Agrobacterium in the production of dsRNA in  [All India 2013] 74. Name the genes responsible for making Bt cotton the host plant. [Delhi 2014] plants resistant to bollworm attack. How do such OR plant attain resistance against bollworm attacks? How has RNAi technique helped to prevent Explain. [Delhi 2012] the infestation of roots in tobacco plants by a nematode Meloidogyne incognita? [Delhi 2016] 75. Name the insect pest that is killed by the products of cryIAc gene. Explain how the gene makes the 65. (a) State the role of DNA ligase in biotechnology. plant resistant to the insect pest. (b) What happens when Meloidogyne incognita  [All India 2010] consumes cells with RNAi gene? [Delhi 2012] 76. Name the source and the type of cry genes 66. Recombinant DNA-technology is of great isolated from it for incorporation into crops by importance in the field of medicine. With the help biotechnologists. Explain how have these genes brought beneficial changes in the genetically of a flow chart, show how this technology has modified crops. [All India 2009] been used in preparing genetically engineered human insulin. [Delhi 2015] 77. What are CRY proteins? Name an organism that OR produces it. How has man exploited this protein to his benefit? [Delhi 2009 C] How did an American Company, Eli Lilly use 78. How does the gene therapy help patients with the knowledge of r-DNA technology to produce ADA-deficiency? [All India 2012 C] human insulin?  [All India 2015] 79. What are cry-proteins? With the help of a suitable OR example, explain how it acts as a biological How did Eli Lilly, using rDNA technique, make pesticide.  [CBSE 2022] it possible to treat diabetic patients with human 80. (a) Why are transgenic animals so called? insulin? Explain.  [All India 2015] (b) Explain the role of transgenic animals in Biotechnology and its Application  257

(i) vaccine safety and (ii) biological products with RNAi are mentioned below. Write the missing steps in its proper sequence. the help of an example each. [Delhi 2013] a.............................................. 81. Explain the various steps involved in the production of artificial insulin. [AIl India 2017] 82. How has the use of Agrobacterium as vectors b. Using Agrobacterium as vector helped in controlling Meloidegyne incognitia introduce it into tobacco infestation in tobacco plants? Explain in correct c.............................................. sequence. [CBSE 2018] 5 Marks Questions d........................................................... 83. One of the main objective of biotechnology is to e. Initiates RNA interference minimise the use of insecticides on cultivated f........................................................... crops. Explain with the help of suitable example how insect resistant crops have been developed g........................................................... using techniques of biotechnology.  [Foreign 2008, Delhi 2009] h........................................................... [All India 2009 C] 89. (a) Name the nematode that infests and damages OR tobacco roots. Explain the application of biotechnology in producing Bt cotton.  [Delhi 2015 C] (b) How are transgenic tobacco plants produced 84. Explain the application of rDNA technology to to solve this problem? [All India 2008] produce insulin. [AIl India 2015 C] 90. Explain the application of rDNA technology to 85. (a) How is mature insulin different from produce insulin. [All India 2015, 2008] proinsulin secreted by pancreas in humans? 91. (a) Name the source from which insulin was extracted earlier. Why is this insulin no more (b) Explain how human functional insulin was used by diabetic people? produced using rDNA technology. (b) Explain the process of synthesis of insulin by Eli Lilly company. Name the techniques used (c) Why is the functional insulin thus produced by the company. considered better than the ones used earlier by diabetic patients? [Delhi 2009] (c) How is the insulin produced by human body 86. Name the process involved in the production of different from the insulin produced by the nematode-resistant tobacco plants using genetic above mentioned company? [All India 2011] engineering. Explain the strategy adopted to 92. Describe the various stages involved in gene develop such plants. transfer for the commercial production of human  [ All India 2009, Foreign 2009, 2011] insulin by Eli Lilly. [Foreign 2011] 87. (a) Why are certain cotton plants called Bt-cotton 93. Give a schematic representation of gene therapy. plants?  [All India 2009 C] (b) Explain how Bt-cotton is resistant to pests. 94. Expand the name of the enzyme ADA. Why is this enzyme essential in human body? Suggest  [Delhi 2011 C] a gene therapy for this deficiency?[All India 2009] 88. Two of the steps involved in producing nematode resistance tobacco plants based on the process of Answers I. Multiple Choice Questions IV. Match the items of Column I with those of Column II: 1. (d) 2. (c) 3. (c) 4. (d) 5. (c) A —(iv) B—(iii) C—(vi) D—(i) 6. (b) 7. (c) 8. (c) 9. (c) 10. (d) E—(ii) 11. (b) 1 Mark Questions II. Fill in the Blanks 1. The lymphocytes in which ADA gene has been 1. patent law 2. toxin introduced are not immortal and patient needs repeated transfusion of such cells, so there is a 3. Farmer’s Right Act, need of periodic treatment. 2. Animals manipulated with the foreign gene 4. Genetically modified organism and have ability to express it are transgenic 5. probe III. True or False 1. False 2. True 3. True 4. True 5. False 258 Biology–12

animals. e.g. Rosie, a transgenic cow produced the toxin binds to the cells of midgut and creates milk containing human alpha lactalbumin. pores. This causes cell swelling and lysis that kills 3. Illegal use of living organism or the products the bollworm. obtained by some multinational companies or other organizations without paying or taking 25. The proinsulin changes to mature insulin when proper authorization from countries or people C-peptide is removed from it. concerned. 4. GEAC makes decisions regarding the validity of 26. (a) Produces inactive protoxin which when GM research and ensures safety of introducing activated can kill cotton bollworm. GM organisms for public services. 5. Transposons act as the source of complementary (b) RNAi is a natural defense mechanism of RNA which binds to specific mRNA in host and eukaryotic cell in which cell produces double forms dsRNA to silence it. stranded RNA which silences mRNA and 6. Virus having RNA genome or Transposons that prevents itself from pathogen. replicate via an RNA intermediate. 7. When nematode consumes cells with RNAi gene, 27. Nematode specific genes are introduced into the cells have both sense and anti-sense RNA, the host plant using Agrobacterium vector. and forms dsRNA and initiates RNAi mechanism This produces both sense and antisense RNA in nematode thus killing it. in host cells farming dsRNA. Upon infection by 8. Plasmid of A. tumefaciens has tumour inducing nematode, this dsRNA initiates RNA interference plasmid and can transfer genes naturally by and silences the mRNA of nematode thus killing delivering a piece of T-DNA. This tumour it. inducing gene can be replaced by desired DNA and is transferred to plants by T-DNA. 28. Bt toxin is released in inactivated form in 9. By virus or Transposons. bacteria but when insect digests it, the alkaline 10. CryIAc and cryIIAb control the cotton bollworms medium of gut activates the toxin and kills the and cryIAb controls corn borer. insect. 11. Nematode cannot live in host that express the special interfering RNA, as the dsRNA does 29. (a) ADA deficiency is caused due to deletion not allow to translate the gene into protein or of gene coding for the enzyme adenosine product. diaminase which is important for proper 12. Root nematode cannot survive in tobacco plant functioning of immune system. when nematode specific genes are introduced into them due to RNA interference. The vectors used (b) Vector used for transferring ADA DNA into are viruses and Transposons. recipient cells in humans is retrovirus. The 13. Enzyme replacement therapy, gene augmentation, recipient cells are lymphocytes. bone marrow transplant. 14. C-peptide keeps the insulin in inactive form 30. Refer answer no. 22. called pro-insulin. 15. Genetically engineered lymphocytes transfusion. 31. Defected gene is replaced by corrected gene in 16. Proinsulin contains chain-a, chain-b and chain-c. lymphocytes of the body. When-c chain is removed, it becomes functional insulin. First attempt was made in correcting the ADA 17. ELISA, PCR deficiency disease. 18. Two short polypeptide chains are linked together by di-sulphide bonds. 32. ‘ c r y ’ g e n e s c o d e f o r C R Y p r o t e i n . T h i s 19. Refer answer no. 17. protein does not allow parasitic lepidopteron larvae 20. Basmati rice. to grow on cotton crop. 21. Biopiracy. 22. Rosie is a transgenic cow whose milk contains 33. Bacillus thuringiensis. Different genes encode human alpha lactalbumin which is nutritionally different proteins which target different insects, more balanced for human infants. e.g. cryIAc and cryIIAb control the cotton bollworms and cryIAb controls corn borer. 22. cry I Ac and cry II Ab. 24. Inactive Bt-toxins is converted into an active protein 34. RNA interference takes place in all eukaryotic organisms as a method of cellular defense. It due to an alkaline pH of the gut of the boll worm, involves silencing of a specific mRNA due to a complementary dsRNA molecule that binds to and prevents translation of the mRNA. Using Agrobacterium vector, nematode specific genes were introduced in the host plant. This produces both sense and anti-sense RNA in host cells. Being complementary, these two strands form dsRNA. Upon infection by a nematode, this dsRNA initiates RNAi and silences mRNA of nematode and the nematode dies. Biotechnology and its Application  259

35. (a) Crops are more tolerant to abiotic stresses 45. Refer answer no. 43. such as cold, drought, salt and heat. 46. Single stranded DNA or RNA, tagged with (b) Have reduced reliance on chemical a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of pesticides by making pest-resistant crops. cells followed by detection using autoradiography. The clone having the mutated gene will hence not (c) Have reduced post harvest losses. appear on the photographic film, because the probe will not have complementarily with the (d) Increased efficiency of mineral usage by mutated gene of cancer. plants which prevents early exhaustion of fertility of soil. 47. Refer answer no. 44. 36. Refer answer no. 34. 48. It is not permanent cure as lymphocytes are not immortal and repeated infusion is required to the 37. Cotton bollworms cause much harm to cotton patients of ADA deficiency. The permanent cure plants when it feeds on it. cryIAc/cryIIAb genes can be achieved if the gene is inserted at early from Bacillus thuringiensis were introduced embryonic stage. into Bt cotton. These genes produce crystals of protoxin. When bollworm bites the cotton 49. Human insulin genes were inserted in bacteria E. fruits, it consumes the toxic insecticidal coli for polypeptide 'A' and 'B' separately. Chains protein. The alkaline pH in its gut activates 'A' and 'B' were extracted and were combined by the toxin. The activated toxin binds to mid-gut creating disulphide bonds to form human insulin. epithelial cells resulting in the lysis of cells leading to the death of the insect. 50. (a) PCR, ELISA and recombinant DNA technology (b) Such techniques are used for early detection 38. Refer answer no. 34. of a disease or a pathogen. 39. Gene therapy is the corrective method employed to a genetic defect in child or at early embryonic 51. Enzyme Linked Immune Sorbent Assay. ELISA stages. In this correct genes are inserted into an is based on the antigen-antibody interaction. individual’s cells and tissues to treat disease. The Infection by pathogen can be detected by the first clinical case where it was used for Adenosine presence of antigens (proteins, glycoproteins, deaminase (ADA) deficiency is a four year old girl etc.) or by detecting the antibodies synthesized child. against the pathogen. 40. Refer answer no. 16. 52. Refer answer no. 51. 41. (a) ADA deficiency. (b) It is caused due to the deletion of the gene 53. Refer answer no. 44. for adenosine deaminase. One cure is bone 54. (a) Biopiracy is the unauthorised use of marrow transplant. bio-resources by multinational companies and other organisations of the countries 42. Adenosine deaminase enzyme is required for without compensatory payment to the people proper functioning of immune system. ADA concerned. deficiency is caused due to deletion of gene for adenosine deaminase. Possible permanent cure (b) The Indian Parliament has cleared the second for this disease is insertion of correct gene at amendment of the Indian Patents Bill, that early embryonic stage. takes issues into consideration including patent terms emergency provisions and 43. (a) Polymerase Chain Reaction is used to detect research and development initiative. HIV in suspected AIDS patients. 55. Biopiracy is the unauthorised use of bio- (b) Enzyme Linked Immuno-Sorbent Assay resources by multinational companies and is used for early diagnosis of a disease other organisations of the countries without and results can be obtained at very low compensatory payment to the people concerned. concentration of pathogen in the body. Hence, it should be prevented. It can be prevented by developing laws to obtain proper authorization 44. In gene therapy, the lymphocytes are cultured and and by paying compensation. functional ADA gene is inserted in lymphocytes by using a retrovirus. These cells are then 56. Insulin is produced in human body in pro- again transferred into the body of patient. Cells hormone inactive form and consists of three not being immortal, patient needs repeated polypeptide chains, A, B and C peptide. The transfusion of such cells. C-peptide is removed during maturation of pro- insulin to insulin. 260 Biology–12

57. (a) DNA ligase is an enzyme which joins two DNA Insulin DNA Vector DNA fragments. Same restriction enzyme cutting both insulin (plasmid) (b) Refer answer no. 34. DNA and vector DNA at specific point 58. (a) Transgenic animals are used to produce products like human protein α-1-antitrypsin Ligases join insulin which is used to treat emphysema, and DNA to plasmid a transgenic cow Rosie produced human proteins containing human α-lactalbumin. Transformation (b) Transgenic animals are made from carry E.coli genes which make them more sensitive to toxic substances than non-transgenic Cells divide animals. They are then exposed to the toxic substances and the effects are studied. 67. Functional adenosine deaminase is administered Toxicity testing in such animals will allow us to the patient by injection repeatedly. to obtain results in less time. Disadvantage: Therapy does not completely 59. Transgenic animals are used to cure the disease so periodic infusion of enzyme (i) Study normal physiology and development required. Enzymes may also cause allergic (ii) Study occurrence and cause of disease reactions in body. (iii) Obtain biological products (iv) Testing vaccine safety 68. Refer answer no. 35. 60. GEAC means Genetic engineering approval 69. Refer answer no. 34. 70. Refer answer no. 34. committee set up by Indian government. This 71. Refer answer no. 37. organization is responsible for validating GM 72. Refer answer no. 37. research, keeping in mind the safety and ethical 73. Refer answer no. 34. concerns of introducing genetically modified 74. Refer answer no. 37. organisms for public utility. 75. Refer answer no. 37. 76. Refer answer no. 37. 61. (a) Plants or bacteria or animals whose genes 77. Refer answer no. 37. have been manipulated. 78. Refer answer no. 44. 79. Cry Protein: The insecticidal protein which (b) Advantages of GMO to a farmer are: (i) Tolerance to abiotic stresses like cold, is produced by soil bacterium named Bacillus thuringiensis is called cry protein. drought, salt, heat (ii) Pest resistant crops reduce reliance on For example: The proteins encoded by the genes crylAc and cryllAb control the cotton bollworms, chemical pesticides The crylAb controls corn borer. (iii) Post harvest loses are lessened (iv) It also provides alternative resource to 80. (a) Transgenic animals are called so because these animals have modified DNA. industries by supplying starches, fuels and pharmaceuticals. (b) (i) Transgenic mice are developed to test (v) Plants absorb less nutrients so the soil safety of polio vaccine before being used remains fertile for longer time. on humans. 62. Refer answer no. 37. 63. Refer answer no. 37. (ii) Human protein, α-1-antitrypsin is used 64. (a) RNA interference to treat emphysema. For explanation, refer answer no.27. (b) Vector used: Agrobacterium tumefaciens 81. Two DNA sequences corresponding to A and 65. (a) DNA ligase is used to join desired fragment B polypeptide chains of human insulin were of DNA with vector DNA. prepared, these were introduced into E.coli (b) Refer answer no. 34. to produce A and B chains separately, these 66. Insulin consists of two polypeptide chains A and B chains were extracted and combined by creating → they are linked by disulphide bonds → Eli Lilly disulphide bonds. company introduced the human genes of both A and B chains into plasmids of E. coli separately → these genes expressed in E. coli in the form of A and B chains → the chains were extracted and mature insulin was produced by formation of disulphide bonds. Biotechnology and its Application  261

82. Using Agrobacterium vector, nematode specific 88. (a) RNAi takes place in all eukaryotic organisms genes are introduced in host plant. This produces as a method of cellular defense. both sense and anti-sense RNA in host cells. Being complementary, these two strands form (b) It produced both sense and anti-sense RNA dsRNA. Upon infection by a nematode, this in the host cells. dsRNA initiates RNAi and silences mRNA of nematode and the nematode dies, thus protecting (c) These two RNAs being complementary to each the plant. other formed a double stranded (dsRNA) 83. Bt toxin gene from Bacillus thuringiensis has (d) Silenced the specific mRNA of nematode. been expressed in cotton plants. Due to which cotton plant became resistant towards insects (e) Parasite could not survive in a transgenic host and no need was left for using insecticides. Bt expressing specific interfering RNA. toxin gene forms protein crystals which is in inactive form called protoxin. Once the insect (f) Transgenic plant therefore got itself protected ingests the inactive toxin, it is converted into from the parasite. active form of toxin due to alkaline pH of the gut which solublizes the crystals, causing death of 89. (a) Meloidegyne incognita the insect. (b) Refer answer no. 34. 84. Refer answer no. 66. 90. Refer answer no. 66. 85. (a) Pro-insuline contains C-peptide chain which 91. (a) Insulin was earlier extracted from the keeps it in inactive form. In mature insulin, pancreas of slaughtered animals. This insulin C-peptide is removed and is functional. was responsible for causing many side effects as it was non-human protein. At present (b) Refer answer no. 66. the insulin produced is recombinant insulin (c) B e f o r e t h e i n s u l i n p r o d u c e d w i t h which has no side effects. biotechnological method was available, (b) In 1983, Eli Lilly, an American company, first patients were given insulin extracted from prepared two DNA sequences corresponding slaughtered cattle or pigs. Patients suffered to A and B chains of human insulin and from allergies due to this insulin. But in introduced them in plasmids of E. coli to rDNA technology the insulin produced is produce insulin chains. These chains A and B expressed by inserting human genes in E. were produced separately and later combined coli, producing no such allergies in the patient by creating disulfide bonds to form human thus making it a better alternative. insulin. 86. Refer answer no. 34. 87. (a) It contains genes obtained from bacteria (c) The insulin produced by humans have Bacillus thuringiensis which kills insect C-peptide and is proinsulin, but the one pests. produced by Eli lilly company is mature insulin without C-peptide. (b) Refer answer no. 37. 92. Refer answer no. 66. 93.     isolated lymphocytes in vitro culture ADA gene inserted Genetically transformed cells selected through retrovirus 262 Transplantation A man with a genetic defect Biology–12

94. Adenosine deaminase. This enzyme is essential for proper functioning of immune system. In gene therapy, the lymphocytes are cultured and functional ADA gene is inserted in lymphocytes by using a retrovirus. These cells are then again transferred into the body of patient. Cells not being immortal, patient needs repeated transfusion of such cells. Assertion & Reason Type Questions For question numbers 1-7: Two statements are permanently by gene therapy. given one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions Reason: The genetically engineered lymphocytes from the codes (a), (b), (c) and (d) as given below. can survive only in culture conditions. (a) Both Assertion and Reason are true and Reason 5. Assertion: Biopatents are awarded for biological is the correct explanation of Assertion. entities and all products derived from them. (b) Both Assertion and Reason are true but Reason Reason: Patent on use of turmeric in wound is NOT the correct explanation of Assertion. healing was cancelled in 2008. (c) Assertion is true but Reason is false. 6. Assertion: Gene therapy is a collection of (d) Assertion is false and Reason is also false. methods that allows correction of a gene defect 1. Assertion: Transgenic food may cause toxicity that has been diagnosed in a child or embryo. or produce allergy. Reason: In gene therapy genes are inserted into a persons cells and tissues to treat a disease. Reason: Transgenic plants have high nutrient content. 7. Assertion: Insulin produced by recombinant DNA technology is more effective than the insulin 2. Assertion: Genetically modified microbes help produced by conventional method. in crop protection. Reason: Insulin produced by recombinant Reason: Transgenic bacteria control insects by DNA technology is more effectively absorbed in producing endotoxins. blood than the insulin produced by conventional method. 3. Assertion: Agrobacterium tumefaciens is called natural genetic engineer. 1. (b) Answers 5. (c) 6. (a) Reason: Agrobacterium tumefaciens infects all 2. (b) 3. (b) 4. (d) broad-leaved agricultural crops but does not 7. (c) infect cereal crops. 4. Assertion: ADA deficiency cannot be cured Case Based Questions 1. Golden rice was engineered from normal rice (iii) In golden rice two genes were taken from by Potrykus and Beyer in the 1990s. The (a) Narcissus sp. (b) Erwinia typical golden colour is due to the production of (c) Oryza sativa (d) None of these b-carotene a precursor of vitamin-A. Golden rice differs from its parental strain by the addition of (iv) Golden rice is helpful to fight against disease caused by the deficiency of three b-carotene genes. These included two genes (a) Vitamin B12 (b) Vitamin C from daffodil plant and third from a bacterium. (c) Vitamin A (d) Vitamin D The incorporation of these genes allows the rice (v) Golden rice was genetically engineered by plant to modify certain metabolic pathways in its (a) Fire and Mello cells to produce b-carotene. (b) Potrykus and Beyer (i) Due to genetic modification golden rice plants (c) Banting and Best produce and store b-carotene in (d) Kohler and Milstein. (a) stem (b) seed 2. Plants having foreign genes in their genome through genetic engineering are called transgenic (c) leaves (d) all of these plants. Genes can be incorporated either through (ii) Transfer of genes to produce golden rice is achieved by a vector or through direct introduction of DNA. Bt cotton is a genetically modified organism which is (a) Agrobacterium (b) pBR322 pest resistant. It contain gene cry I Ac and cry II (c) l-phage (d) gene gun. Ab of Bacillus thuringiensis. It is used to control Biotechnology and its Application  263

lepidopterans, coleopterans and dipterans. Bt phenotypic properties including growth rate, fat cotton can resist cotton bollworm and produce composition, milk production, hair texture, etc. higher yields. Cry gene produces cry protein or (i) The production of transgenic animals includes Bt toxin. It is an endotoxin which remains as (a) Identification and separation of desired protoxin plants and converted to active toxin gene after getting ingested by the insects. Alkaline pH (b) Combining the desired gene with of the insect gut solubilises the protein crystals, appropriate vector the activated toxin creates pores to the mid guts (c) Introduction of vector in cells, tissues or wall of the insects which cause them to death. embryos (i) Bt cotton crops are (d) All of these (a) Fungal resistant (b) Droughtresistant (ii) In transgenic animals, i.e., cow and sheep (c) Insect resistant (d) All of these proteins of pharmaceutical value are produced (ii) Cotton bollworms are killed by the protein in large quantities in the encoded by the gene (a) Blood (b) Accumulated fat (a) cry I Ac (b) cry I Ab (c) Mammary glands (d) None of these (c) cry II Ab (d) both (a) and (c) (iii) Mouse is mostly preferred animals for studies on gene transfer because (iii) Which of the following is not an advantage of A. Short oestrous cycle GM crops? B. Long gestation period (a) GM plants can cause gene transfer to C. Short generation time non-target plant species. D. Production of one or two offspring per (b) GM plants have helped to reduce post pregnancy harvest losses. (a) Both (A) and (C) (b) Both (A) and (B) (c) GM plants are more tolerant to abiotic stresses. (c) Only D (d) Both (C) and (D) (d) GM plants enhance nutritional value of (iv) Transgenic genes alter many phenotypic properties including food. (a) Growth rate (b) Fat composition (iv) Bacillus thuringiensis is a (c) Milk production (d) All of these (a) Food borne bacteria (v) Assertion : Transgenic mice have been (b) Air borne bacteria engineered to express human antibodies. (c) Soil borne bacteria Reason : Large segment of human DNA encoding human immunoglobulin have been (d) Soil borne fungus (v) Assertion: Cotton bollworms are killed by transferred to mice. ingesting the leaves of the transgenic plant. (a) Both assertion and reason are true and Reason: Bt toxin binds with the midgut wall reason is the correct explanation of of the insect and make pores in them. assertion. (a) Both assertion and reason are true and (b) Both assertion and reason are true and reason is the correct explanation of reason is not the correct explanation of assertion. assertion. (b) Both assertion and reason are true but (c) Assertion is true but reason is false. reason is not the correct explanation of (d) Both assertion and reason are false. assertion. 4. Insulin used to cure diabetes was earlier extracted from pancreas of slaughtered cattle and (c) Assertion is true but reason is false. (d) Both assertion and reason are false. pigs. Insulin extracted from an animal source, 3. Transgenic animals can serve as factories that though caused some patients to develop allergy in some cases, may produce large amount of or other types of reactions to the foreign protein. proteins more efficiently. Transgenic mice have Human insulin consists of two short polypeptide been engineered to express human antibodies chains : chain A and chain B, that are linked by introducing large segment of human DNA together by disulphide bridges. In mammals encoding human immunoglobulin genes. In including humans, insulin is synthesised as a transgenic large animals such as cow or sheep pro-hormone which contains an extra stretch proteins of pharmaceutical value can be produced called the C-peptide. This C peptide is not in large quantities in milk which is later present in mature insulin and is removed during purified. Transgenesis can be used to alter many maturation into insulin. 264 Biology–12

(i) Identify A in the given figure (iv) Why is the bioreactor important for the production of human insulin by transgenic (a) Polypeptide chain A bacteria? (b) Polypeptide chain B (a) It provides the low-oxygen conditions that are important for insulin production. (c) Polypeptide chain C (b) It provides optimal conditions for the (d) None of these transgenic to multiply rapidly. (ii) The following is a list of some stages involved (c) It facilitates the extraction and purification of insulin from the transgenic bacteria. in producing human insulin from genetically (d) It maximise the rate of fermentation of engineered bacteria. the transgenic bacteria. 1. The bacteria are cultured in a fermenter (v) A bacteriologist carries out his first attempt at engineering E.coli with the gene for human for large scale production. insulin. During the process, he realises that his stock of DNA ligase has depleted but 2. Recombinant insulin is extracted from decides to continue anyway. What is a likely consequence of his decision? the bacterial cells that expresses insulin (a) The resulting plasmids are not able gene. to enter the E. coli bacteria even after applying heat shock. 3. The same restriction enzymes is used (b) Bacteria with the rDNA will not be able again to cut the bacterial plasmid for to form colonies in a fermenter. insertion of the human insulin gene. (c) The bacterial plasmids do not have sticky ends and are unable to accommodate the 4. Bacteria take up the plasmid carrying the human gene. insulin gene. (d) The resulting E. coli bacteria do not contain the human insulin gene. 5. A restriction enzyme is used to cut human 5. Severe combined immuno deficiency (SCID) is DNA to extract the insulin gene. a group of rare disorders caused by mutations in different genes involved in the development Select the correct order of these stages. and function of infection-fighting immune cells. Infants with SCID appear healthy at birth but (a) 4, 5, 3, 2, 1 (b) 5, 3, 4, 1, 2 are highly susceptible to severe infections. The condition is fatal, usually within the first year (c) 1, 5, 3, 4, 2 (d) 2, 4, 3, 5, 1 or two of life, unless infants receive immune- restoring treatments, such as transplants (iii) To insert the insulin gene into bacterial DNA, of blood-forming stem cells, gene therapy, or enzyme therapy. More than 80 percent of both the bacterial plasmid and the human SCID infants do not have a family history of the condition. However, development of a chromosome containing the insulin gene are newborn screening test has made it possible to detect SCID before symptoms appear, helping treated with the same restriction enzyme. ensure that affected infants receive life-saving treatments. Gene therapy is the process of Using the same restriction enzyme ensures introduction of DNA into an organism e.g. human beings in order to treat a disease. It is used to that replace a missing gene product or to correct mutant alleles. ADA is an autosomal-recessive (a) DNA ligase is able to join the segments of inherited disorder that occurs due to defective adenosine deaminase (ADA) enzyme. Person human and bacterial DNA with this enzyme deficiency suffer from severe combined immunodeficiency (SCID) conditions. (b) the exact length of nucleotides matching the insulin gene is removed from the plasmid (c) both the bacterial and human DNA will contain sticky ends (d) Sticky ends in the cut plasmid and insulin gene are complementary. Biotechnology and its Application  265

Human gene therapy trial can be used for ex (i) Stem cells are widely used in medical research. Which property of stem cells makes vivo introduction of functional ADA gene in them particularly useful in this research? bone marrow cells of the patient, suffering from (a) T h e y c a n d i v i d e a n d b e m a d e t o differentiate into various types of cell. SCID. For this process, an engineered retrovirus (b) They will continue to divide indefinitely. containing a functional ADA gene is used to (c) They can be fused together to form a transfer the ADA gene into stem cells isolated zygote. (d) They can divide and eventually give rise from the patient with SCID. The treated cells to a whole organism. or modified cells with the good ADA gene are (ii) Stem cells can be divided into four main reintroduced into the patients' marrow. types. Which of the four types of stem cell can differentiate into a limited range of tissues? (i) ADA deficiency is a ___________. (a) Zygotic stem cells (b) Fetal stem cells (a) Autosomal-recessive inherited disorder (c) Embryonic stem cells (d) Adult stem cells (b) Sex linked recessive inherited disorder (iii) Which feature of stem cells obtained from blood in the umbilical cord enables their use (c) Sex linked dominant inherited disorder in the treatment of a variety of blood cancers? (a) They are totipotent. (d) Autosomal-recessive inherited disorder (b) They can replace blood stem cells affected (ii) Infants with ADA deficiency are by cancer. (c) They can differentiate into any cellular (a) Healthy at birth but are highly susceptible to severe infections. component of blood. (d) They can differentiate into bone marrow (b) Healthy at birth but and develop resistant to severe infections later on cells. (iv) The search for pluripotent stem cells is (c) They are very sick at the time of birth intense. The spermatogonium is the diploid (d) None of these precursor of haploid sperm in the development pathway of mouse gametes as shown below. (iii) Infants with ADA deficiency are also called (a) AIDS (b) SCID Scientists were interested to find out which (c) HLA Deficient (d) None of these stages of sperm development have stem cell capacity. Two experiment were carried out (iv) ADA deficiency may occur in a child if the using sterile host males with testes that parents are lacked germ cells. The results are shown in the table. (a) Both dominant for the ADA gene (b) One is heterozygous and the other parent is dominant for both the genes (c) Both are heterozygous for the genes (d) It is not heritable. (v) The permanent cure of ADA deficiency is by (a) Enzyme replacement therapy (b) Gene therapy after attaining age more than 5 years (c) Gene therapy at embryonic stage (d) Bone marrow transplant 6. Stem cells hold the potential for manifold applications in biotechnology based next generation therapeutics. Scientists are trying to formulate better and more personalised treatment modalities against some seemingly irremediable diseases by harnessing body's own stem cells and stem cell niche. Stem cells of different origin and level of potency are being investigated for tissue regeneration, treatment of bone defect, drug testing, gene therapy and cell based therapy for muscle damage, spinal cord injury, cancer therapy, etc. The properties of embryonic and adult stem cells to either self- renew or differentiate into multiple cell lineages make them an attractive source for cell therapies, tissue engineering and as model system for drug screening. 266 Biology–12

Type of cells Result (a) ESCs show plasticity. (b) ESCs are pluripotent. used (c) ESCs are capable of dividing. (d) ESCs are multipotent. Experiment Secondary Fertility was not A ns. 1. (i) (b) (ii) (a) (iii) (a) (iv) (c) 1 spermatocytes restored (v) (b) 2. (i) (c) (ii) (d) were injected (iii) (a) (iv) (c) (v) (a) Experiment Spermatogonia Fertility was 3. (i) (d) (ii) (c) (iii) (a) (iv) (d) 2 were injected restored for the (v) (a) 4. (i) (c) (ii) (b) rest of the mouse's (iii) (d) (iv) (b) (v) (d) life 5. (i) (a) (ii) (a) (iii) (b) (iv) (c) What property of a stem cell is missing in the (v) (c) 6. (i) (a) (ii) (d) secondary spermatocytes? (iii) (c) (iv) (b) (v) (b) (a) Commitment (b) A proper stem-cell niche (c) Self-renewal (d) Specialisation (v) Which feature of embryonic stem cells (ESCs) is illustrated below? Blastocyst ESCs Hematopoietic Neural Mesenchymal SCs SCs SCs qqq Blood cells Cells of nervous system Connective tissue, bones, cartilage etc. Biotechnology and its Application  267

Topics Covered 11 Organisms and Populations 11.1 Populations ORGANISMS AND POPULATIONS Gametogenesis C hapter map Population Attributes Population Growth Population Interaction • Population • Mutualism  density • Natality • Mortality • Competition • Sex ratio • Predation • Age pyramids • Immigration • Emigration • Parasitism • Amensalism • Growth Models:   (i) Exponential (ii) Logistic Ecology is the study of interactions of organisms with other organisms and also with their physical environment. Ecology is concerned with four levels of biological organisation–organism, population, communities and biomass. Topic 1. Populations Group of individuals living together in a defined area and share similar resources, and breed with each other is called population. Population Attributes Birth rate and death rate: Change in number with respect to the members of population refers to per capita births and deaths. Sex ratio: Ratio of male and females in a population. Age distribution: Individuals of different age groups present at any given time. If it is plotted graphically we get following three types of age pyramids: Post-reproductive Reproductive Pre-reproductive Expanding Stable Declining Population Population Population Population density: Number of individuals per unit area. Sometimes only relative number is considered as in case of fish in a lake, tigers in a forest. Alternately, in the case of 200 Parthenium plants growing in a fallow land with single banyan tree in its vicinity, the biomass becomes more relevant. 268

Population Growth if (b – d) = r • Population can increase or decrease due to following then dN = rN factors: dt Natality (B): Total number of births in given period of time. where ‘r’ is intrinsic rate of natural increase and Mortality (D): Total number of deaths in given helps to assess the impact of biotic and abiotic period of time. factors on population growth. Immigration(I): Number of individuals which migrate in a habitat to live. For above equation if growth is plotted against time, Emigration(E): Number of individuals which J-shaped curve is obtained. The integral form of leave the habitat. exponential growth equation is written as • If N is the population density at a given time t, then Nt = N0ert population growth is given by where Nt = Population density after time t, N0 = Nt+1 = Nt + [(B + I) – (D + E)] Population density at time zero and e = the base of natural logarithms (2.71828) Immigration (I) Logistic Growth + When a population is growing exponentially, Natality (B) + Population – Mortality (D) there will be competition between individuals for Density resources and the theory of survival for the fittest (N) implied. The population will not grow beyond its carrying capacity K. – Emigration (E) Factors influencing population density Population density (N) K Population density (N) Growth Models dN = rN K – N Following two growth models show us that how nature dt K controls population growth. b Exponential Growth • When resources in the habitat are unlimited, each Time (t) species has the ability to realise its innate potential For this type of population growth if we plot growth is fully to grow in number, and population grows against time, we get sigmoid curve and is represented exponentially. as • If at any given time t, population size is N, birth rate is b and death rate is d, then there is increase dN = rN  K − N  or decrease in N during a unit time dt K dN = rN Where, a dt K N = Population density at time t r = Intrinsic rate of natural increase K = Carrying capacity. Time (t) Life History Variation It is expressed as: Individuals in a population tend to evolve and gain high r value or reproductive fitness. Many of them dN = (b – d) × N are adapted to have an efficient reproductive strategy, dt e.g. Pacific salmon and bamboo breed only once in their lifetime, oysters and pelagic fishes produce large number of small sized offsprings, birds and mammals produce large sized few offsprings. Organisms and Populations  269

Population Interactions • In Galapagos Island, Abingdon tortoise got extinct due to greater browsing efficiency of goats which In a community all individuals interact with each were introduced in island. other. Such interaction can be summarised as given in the table. '+' sign indicates beneficial interaction, • Competitive release: Species whose distribution is – sign indicates detrimental and 0 indicates neutral restricted to a small geographical area because of the interaction (no affect on other organism). presence of a competitively superior species, is found to expand its distributional range dramatically when Population Interactions the competing species is experimentally removed. e.g. in Connell’s elegant field experiment, the Species Species Name of larger and competitively superior Barnacle Balanus AB Interactions dominates the intertidal region of rocky sea coasts ++ of Scotland. The smaller barnacle Chathamalus was Mutualism excluded from that zone. Later in the experiment when Balanus was removed, Chathamalus expanded – – Competition their distributional range. + – Predation • Competitive Exclusion Principle: Two closely related species competing for same resources cannot + – Parasitism co-exist indefinitely. This is not true in case when resources are unlimited. – 0 Amensalism • Mac Arthur showed that five species of Warblers Predation coexisted even when resources were limited as they avoided competition by resource partitioning, • Predators are part of a food chain where primary i.e. due to behavioural differences in their foraging consumer is eaten by secondary consumer which in habits. turn is eaten by tertiary consumer. Parasitism • Predators keep prey population under control to maintain ecological imbalance. • Parasitism has mostly evolved to be host specific in such a way that both tend to co-evolve i.e. if host • In the absence of natural predators, the new species develops a mechanism to avoid parasite, the parasite introduced in an area becomes invasive, e.g. Prickly too evolves and develops mechanism to stay with pear cactus when introduced in Australia in early the same host. 1920’s became invasive and could be brought under control only when its natural predator a cactus Parasites have certain adaptive features such as: feeding moth was introduced. – Loss of unnecessary sense organs • In an experiment, when a predator starfish Pisaster was removed from enclosed intertidal area, more – Presence of adhesive organs or suckers than 10 species of invertebrates became extinct within a year because of inter specific competition. – Loss of digestive system • Alternately, to prevent predation, various defence – High reproductive capacity mechanisms have been adapted by different species, e.g. some insects and frogs can camouflage in – Life cycle of parasites is complex and involves background, monarch butterfly becomes poisonous two or more intermediate hosts. e.g. human and distasteful and the predator avoids eating it. liver fluke, a flat worm, has two intermediate This is acquired at larval stage by feeding on a hosts, a snail and a fish, Plasmodium, a poisonous weed. malarial parasite has two hosts – humans and mosquito. • Plants produce variety of chemicals to avoid grazing, such as nicotine, caffeine, quinine, strychnine, • Parasite harms the host by reducing its survival, opium. Cattle never browse on Calotropis, it growth, reproductive capacity and makes it produces highly poisonous cardiac glycosides. physically weak rendering it vulnerable to predation. Morphological modifications like thorns, spines etc. also help plants from grazers. • Parasites which obtain their nutrition from external surface of the host are called ectoparasites, e.g. lice Competition on humans and dogs, copepods on fishes, Cuscuta on hedge plants. Cuscuta lost its chlorophyll and leaves • Competition occurs between closely related species to evolve in to a parasite. or unrelated species for the same resource. • Parasites which obtain their nutrition by living • In some shallow lakes of America, flamingos and inside the body of host are called endoparasites, e.g. fishes compete for zooplanktons as their food. hook worm, tape worm, Ascaris. • Gauss concluded by his experiments that when resources are limited, the competitively superior species will eliminate the other species. 270 Biology–12

• Koel lays its eggs in the nest of a crow. Crow fails get fruits from trees and also act as seed dispersal to identify koel's eggs from its own due to similar agents. size and colour and incubates them as its own. This phenomenon is called brood parasitism. • The obligatory mutual relationship is established between fig and a wasp. The female wasp uses the Mutualism fruit for oviposition, uses seeds within the fruit for nourishing its larvae, in turn the wasp pollinates • In lichens, both partners, fungi and algae derive the flowers of fig in inflorescence. Fig can only get benefit from each other in terms of absorption of pollinated by none other than partner wasp species. nutrition by fungi and providing photosynthetic products by the algae. • Interesting phenomenon is shown by some orchids called sexual deceit. An orchid, Orphys, has • Similarly in mycorhhiza, the association is between developed one of its petal in such a way that it fungi and the roots of higher plants. Fungi absorbs resembles a female bee. When male bee visits flower nutrition (Phosphorous) from soil and plant provide to pseudocopulate, it pollinates the flower. It also photosynthetic products. shows the phenomenon of coevolution. If female bee changes the colour or pattern, the orchid too has to • Animals like bees help in pollination, in turn insects evolve to gain resemblance. get nectar and pollens. If birds are pollinators, they EXERCISE I. Multiple Choice Questions (c) It will increase (d) It will first decline and then stabilise 1. Autoecology is the: 7. What parameters are used for tiger census in our (a) Relation of a population to its environment country’s national parks and sanctuaries? (b) Relation of an individual to its environment (a) Pug marks only (c) Relation of a community to its environment (b) Pug marks and faecal pellets (c) Faecal pellets only (d) Relation of a biome to its environment (d) Actual head counts 8. Which of the following would necessarily decrease 2. Ecotone is: (a) A polluted area the density of a population in a given habitat? (b) The bottom of a lake (a) Natality > mortality (b) Immigration > emigration (c) A zone of transition between two communities (c) Mortality and emigration (d) Natality and immigration (d) A zone of developing community 3. Biosphere is: (a) A component in the ecosystem (b) Composed of the plants present in the soil (c) Life in the outer space II. Fill in the Blanks (d) Composed of all living organisms present 1. Lice is a ______ . on earth which interact with the physical 2. One species is harmed whereas the other is environment unaffected is called ____ . 4. Ecological niche is: (a) The surface area of the ocean 1 Mark Questions (b) An ecologically adapted zone 1. When and why do some animals like snails go into aestivation? [All India 2008] (c) The physical position and functional role of a species within the community 2. What do phytophagous insects feed on? (d) Formed of all plants and animals living at the [Delhi 2012] bottom of a lake 3. What does nature’s carrying capacity for a species indicate ? [Foreign 2016] 5. If a population of 50 Paramoecium present in a pool increases to 150 after an hour, what would 4. Mention any two significant roles predation plays be the growth rate of population? in nature. [All lndia 2008] (a) 50 per hour (b) 200 per hour 5. Give example of an organism that enters ‘diapause’ and why? [Delhi 2014] (c) 5 per hour (d) 100 per hour 6. How does camouflage help an insect? 6. A population has more young individuals [All India 2009 C] compared to the older individuals. What would be the status of the population after some years? 7. How do herbs and shrubs survive under the (a) It will decline shadow of big canopied trees in forests? (b) It will stabilise [Delhi 2008 C] Organisms and Populations  271

8. List two advantages that a mycorrhizal associa- 24. Give an example where percentage cover is a tion provides to the plant. [Delhi 2008 C] more meaningful measure of the population size. 9. What does ecological niche of an organism [Delhi 2008 C] represent?[Delhi 2007] 25. Name the two intermediate hosts on which the 10. How do prickles help cactus survive in desert? human liver fluke depends to complete its life cycle Give two methods. [All India 2010 C] so as to facilitate parasitisation of its primary host. [Delhi 2014] 11. Write the basis on which an organism occupies a 26. Mention the unique feature with respect to space in its community/natural surroundings. flowering and fruiting in bamboo species. [Delhi 2012] [All India 2013] 27. In a pond, there were 200 frogs. 40 more were born in a year. Calculate the birth rate of the 12. Name the interaction that exists between population.[Delhi 2010] Cuscuta and shoe-flower plant. 28. Why do predators avoid eating monarch butterfly? How does the butterfly develop this protective [All India 2014, Delhi 2015 C] feature?[Foreign 2010] 29. How is Cuscuta adapted to be a parasitic plant? OR [Delhi 2008 C] What is the interaction called between Cuscuta and shoe flower bush? [Delhi 2012] 13. Name the type of interaction seen between fig and wasps. [All India 2015 C] 30. (a) Immigration 14. State Gauss’s competitive exclusion principle. [All India 2014] 15. Name the type of association that the genus B Population D A Glomus exhibits with higher plants. [All India 2014] Emigration 16. Describe the mutual relationship between fig tree Observe the schematic representation given and wasp and comment on the phenomenon that above and answer the following questions: operates in their relationship. [All India 2014] (i) Identify A and B. (ii) Calculate the growth rate of bacteria in a curd 17. Construct an age pyramid which reflects an expanding growth status of human population. sample, where 1 million bacteria increased to two million, within a period of one hour. [All India 2014] OR 18. Name the interspecific interaction in which one is detrimental while the other is neutral. (b) Post Reproductive [All India 2013 C] 19. Pollinating species of wasps show mutualism with specific fig plants. Mention the benefits the female wasps derive from the fig trees from such Reproductive an interaction. [All India 2011] 20. Why are cattle and goats not seen browsing on Pre Reproductive Calotropis growing in the fields? [Foreign 2011] Identify the type of pyramid given above. Write OR the identifying feature on the basis of which you Why do cattle avoid grazing on Calotropis plants? identified it. [CBSE 2022] Explain.[Foreign 2009] 2 Marks Questions 21. If 8 individuals in a laboratory population of 80 fruitflies died in a week, then what would be the 31. Differentiate between parasitism and competition, giving one example of each. State the common death rate for population for the said period? characteristic they share. [Foreign 2015] [Delhi 2010] 32. Construct an age pyramid which reflects a stable 22. In a pond there were 20 Hydrilla plants. Through growth status of human population. [Delhi 2014] reproduction 10 new Hydrilla plants were 33. Explain Verhulst-Pearl Logistic Growth of a added in a year. Calculate the birth rate of the population.[Foreign 2014] population.[Delhi 2010] 34. Explain mutualism with the help of an example. 23. Give one example where population estimation of [Delhi 2014 C] an organism is done indirectly without actually 35. Why are a fig tree and its partner wasp considered counting the organism. [Delhi 2008 C] a good example of mutualism? [Delhi 2013 C] 272 Biology–12

36. How does the floral pattern on Medi-terranean (b) How does predation differ from parasitism? orchid Ophrys guarantee cross pollination? [Foreign 2016] [Foreign 2009, Delhi 2010] 52. (a) A parasite has to adapt to be able to live in the 37. Mention the changes the koel must have host. Write the various parasitic adaptations. undergone in order to achieve brood parasitism, during the course of evolution. [All India 2010 C] (b) Mention an adaptive feature exhibited in brood parasitism in Koel and Crow. 38. Egrets are often seen along with grazing cattle. How do you refer to this interaction? Give a [Foreign 2016] 53. Co-evolution is a spectacular example of reason for this association. [Delhi 2009] mutualism between an animal and a plant. 39. (a) What is “r” in the population equation given Describe co-evolution with the help of an below: example.  [Foreign 2016] dN/dt = rN 54. Name the type of interaction seen in each of the (b) How does the increase and the decrease in following examples: the value of ‘r’ affect the population size? (i) Ascaris worms living in the intestine of human  [Delhi 2009] (ii) Wasp pollinating fig inflorescence 40. In a pond there were 40 lotus plants. After a year (iii) Clown fish living among the tentacles of sea- the number rose to 56. Calculate birth rate of a anemone lotus plant. [All India 2009 C] (iv) Mycorrhizae living on the roots of higher 41. Name the interaction in each of the following: plants (a) Cuckoo lays her eggs in the crow’s nest. (v) Orchid growing on a branch of a mango tree (b) Orchid grows on a mango tree. (vi) Disappearance of smaller barnacles when (c) Ticks live on the skin of dogs. Balanus dominated in the Coast of Scotland. (d) Sea anemone is often found on the shell of [All India 2011] hermit crab. [Delhi 2008] 55. Study the graph given below and answer the 42. Certain species of wasps are seen to frequently questions that follow: visit flowering fig trees. What type of interaction is seen between them and why? [All India 2008] 43. What does S-shaped pattern of population growth Population density (N) represent? How is J-shaped pattern different from A it and why? [Delhi 2007] B 44. How does monarch butterfly defend itself from predators? Explain. [Delhi 2013 C] 45. How do plants benefit from having mycorrhizal symbiotic association? [Foreign 2010] 46. (a) How is Cuscuta adapted to be a parasitic Time (t) plant? (a) Write the status of food and space in the (b) Why do cattle avoid grazing on Calotropis curves A and B. plants? Explain. [Foreign 2009] (b) In the absence of predators, which one of the 3 Marks Questions two curves would appropriately depict the prey population? 47. Predation is usually referred to as a detrimental association. State any three positive roles that a (c) Time has been shown on X-axis and there is a parallel dotted line above it. Give the predator plays in an ecosystem. [All India 2016] significance of this dotted line. [Delhi 2014] 48. What is mutualism? Mention any two examples 56. Draw and explain expanding age pyramids of where the organisms involved are commercially human population. Why is it so called? exploited in agriculture.  [All India 2015] [All India 2014 C] 57. (a) Write the importance of measuring the size 49. Name and explain the type of interaction that exists in mycorrhizae and between cattle egret of a population in a habitat or an ecosystem. and cattle.  [All India 2015–16] (b) Explain with the help of an example how the percentage cover is a more meaningful 50. Differentiate between mutualism, parasitism and measure of population size than more commensalism. Provide one example for each of numbers.[All India 2013] them.[Foreign 2015] 58. (a) Explain “birth rate” in a population by taking a suitable example. 51. (a) Explain any two defense mechanisms plants evolved against their predators. Organisms and Populations  273

(b) Write the other two characteristics which only (d) What is symbolised by N? [Delhi 2008] a population shows but an individual cannot. 65. Study the population growth curves shown below: [All India 2013] 59. (a) Explain “death rate” in a population by taking A a suitable example.Population density Population density (N) K (b) Write the other two characteristics which only B a population shows but an individual cannot. 60. [All India 2013] A ks Time (t) Time (t) (a) Identify curves ‘A’ and ‘B’. (b) Mention the conditions responsible for the A forest hardly has any carnivores. Census of herbivorous mammals was taken and plotted as curves ‘A’ and ‘B’ respectively. a graph shown above. Identify the curve that will (c) Give the necessary equation for the curve ‘B’. [All India 2008] explain the population growth of herbivores. Give 66. Plot a logistic growth curve. Describe nature’s reason to your answer. [All India 2013 C] carrying capacity for a species in a particular 61. (a) List any three ways of measuring population density of a habitat. habitat.[All India 2008 C] 67. Name the interaction in each of the following: (b) Mention the essential information that can be (a) Ascaris worms living in the intestine of obtained by studying the population density human. of an organism. [All India 2012] 62. Explain with the help of an example each of (b) Sucker fish attached to the shark (c) Smaller barnacles disappeared when Balanus dominated in the coast of Scotland. (d) Wasp pollinating fig inflorescence. [Delhi 2008] 68. Study the three different age pyramids, for human population given below and answer the questions that follow: the three population interactions where the organisms live closely together.[All India 2011 C] 63. Why is predation required in a community of different organisms? A BC  [All India 2008, Foreign 2009] 64. Study the population growth curves in the graph (a) Write the names given to each of these age pyramid. given below and answer the questions which (b) Mention the one which is ideal for human follow: population and why? [Foreign 2011] 5 Marks Questions Population density (N) A 69. (a) Name the two growth models that represent K population growth and draw the respective growth curves they represent. B (b) State the basis for the difference in the shape of these curves. (c) Which one of the curves represent the human population growth at present? Do you think such a curve is sustainable? Give reason in Time (t) support of your answer.  [All India 2016] (a) Identify the growth curves ‘A’ and ‘B’. 70. “Analysis of age-pyramids for human population can provide important inputs for long-term (b) Which one of them is considered a more realistic one and why? planning strategies.” Explain.  [Delhi 2015] OR (c) If dN = rN  K − N is the equation of the dt  K  (a) Represent diagrammatically three kinds of age-pyramids for human populations. logistic growth curve, what does K stand for? 274 Biology–12

(b) How does an age pyramid for human 73. (a) Explain the equation: population at given point of time helps the Nt + 1 = Nt + [(B + I) – (D + E)] policy makers in planning for future. on the basis of the flow chart given below:  [Delhi 2016] Immigration (I) 71. (a) List the different attributes that a population (+) (–) has and not an individual organism. Mortality (D) (b) What is population density? Explain any three (+) Population Natality (B) density (N) different ways the population density can be measured, with the help of an example each. (–)  [All India 2015] Emigration (E) 72. (a) Name the population growth pattern the (b) Mention the different ways by which the  rN population density of different species can be equation dN = represents. measured.[Delhi 2011 C] dt 74. (a) Compare, giving reasons, the J-shaped and What does “r” represent in the equation? Write its importance in population growth. S-shaped models of population growth of a (b) Explain the principle of carrying capacity species. by using population Verhulst-Pearl logistic (b) Explain ‘‘fitness of a species’’ as mentioned by growth curve. [All India 2014 C] Darwin. [All India 2017] Answers I. Multiple Choice Questions 11. Ecological niche and feeding relationships among organism. 1. (b) 2. (c) 3. (d) 4. (c) 5. (d) 6. (c) 7. (b) 8. (c) 12. Parasitic interaction 13. Mutualism II. Fill in the Blanks 14. Two closely related species if compete for same 1. ectoparasite 2. amensalism resources cannot co-exist. This is not true in case 1 Mark Questions when resources are unlimited. 15. Mutualism 1. To prevent themselves from heat and water loss 16. An obligatory mutual relationship can be seen during summers. in fig tree and a wasp. The female wasp uses the fruit for oviposition, uses seeds within the 2. Cactus fruit for nourishing its larvae, in turn the wasp pollinates the flowers of fig in inflorescence. 3. This indicates the possible number of individuals Fig can only get pollinated by none other than in a population which can be supported by the partner wasp species. resources available. 17. Post-reproductive 4. (a) They transfer energy from one trophic level to the next trophic level. Reproductive (b) They keep prey population under control. Pre-reproductive 5. Zooplanktons undergo diapauses if the conditions Expanding Population are unfavourable. 18. Ammensalism 6. This is a defence mechanism developed by insects 19. Female wasp lays its eggs in the fruits of fig. to avoid predation by cryptic colouration. The larvae use seeds within the fruit for their 7. Herbs and shrubs survive under the shadow of big nourishment. This is an example of mutualism. canopied trees in forest because they are adapted to photosynthesise optimally under very low light 20. Cattle never browse on Calotropis because conditions. it produces highly poisonous cardiac glycosides 8. Mycorrhiza absorbs nutrients from soil and give 21. Death rate = No. of individuals dead them to plants and plants provide carbohydrates Total no. of individuals to mycorrhiza = 8 = 0.1 9. The ecological niche of an organism represents 80 the range of conditions that it can tolerate, the resources it utilizes, and its functional role in the ecological system. 10. Prickles reduce transpiration and conserve water and they help to prevent browsing by cattle. Organisms and Populations  275

22. Birth rate = No. of individuals born When a population is growing exponen-tially, Total no. of individuals there will be competition between individuals for resources and the theory of survival for the = 10 = 0.2 plants per year. fittest will be applied. The population will not 20 grow beyond its carrying capacity K. 23. Fish caught per trap in a pond or pugmarks of tigers in a forest. If we plot growth against time, we get sigmoid curve and is represented as 24. One single large banyan tree in grassland. 25. Snail and fish. dN/dt = rN (K – N) 26. They flower once in lifetime. K Where 27. Birth rate = No. of individuals born Total no. of individuals N = population density at time t r  = intrinsic rate of natural increase = 40 = 0.2 frogs/years K = carrying capacity 200 28. Monarch butterfly is highly distasteful as it is 34. In mutualism the two interacting organisms are poisonous. The Butterfly acquires this chemical mutually benefitted. Example: In lichens, both partners, fungi and algae derive benefit from during caterpillar stage by feeding on a poisonous each other in terms of absorption of nutrition by fungi and providing photosynthetic products by milkweed. the algae. 29. It lost its chlorophyll and leaves in course of 35. Female wasp lays its eggs in the fruit. This wasp evolution. pollinates the flowers present in inflorescence while searching for suitable site for egg laying. 30. (a) (i) A-Mortality, B-Natality (ii) 100% (b) The given pyramid is expanding. The 36. The orchid Orphys has developed one of its petal in such a way that it resembles a female bee. population of pre-reproductive is higher than When bee visits flower to pseudocopulate, it the post reproductive population, which make pollinates the flower. the expanding pyramid of population. 2 Marks Questions 31. Parasitism Competition T w o i n t e r a c t i n g Competition happens 37. Koel’s eggs resemble of that of crow with respect to shape, size and colour, which must have organisms where between closely related happened in due course of evolution. This reduces chances of identification and rejection by the one gets benefit and species or unrelated crow. other gets harmed, species for the same the parasite gets resource, both interacting 38. Egrets feed near to the grazing cattle, as the nutrition from the species get no benefit cattle move around, they stir up and flush out host organism. the insects from vegetation which are then eaten from each other by egrets. e.g. tapeworm in e.g. flamingos and fishes 39. (a) ‘r’ is intrinsic rate of natural increase. human alimentary compete for zooplanktons (b) Population size increases with the increase canal. as their food in ‘r’ and it decreases with the decrease of ‘r’. 32. 40. The birth rate of lotus plant Stable = Number of individuals born 46 0.4 Total number of individua=ls 4=0 33. Birth rate is 0.4 per lotus plant per year. Population density (N) K 41. (a) Brood parasitism (b) Commensalism dN = rN K –N dt K (c) Parasitism Time (t) (d) Commensalism 42. Refer answer no. 16. 43. S-shaped pattern of population growth represents logistic growth of a population. In this, population grows till it reaches carrying capacity of the environment. In J-shaped pattern of population 276 Biology–12

growth, the population shows exponential (b) Predation Parasitism growth. The population grows indefinitely when • Predator feeds on • Parasite lives and resources are unlimited. prey feeds on host 44. Refer answer no. 28. • Predator is not • Parasite is mostly host specific host specific 45. Mycorrhiza is the mutual association between fungus such as 'Glomus' with the roots of higher • Predator helps • Parasite tends plants. The fungus helps in absorbing nutrients such as phosphorous to the plants and in turn to check prey to co-evolve with gets food shelter from the plants. population host 46. (a) Refer answer no. 29. (b) Calotropis produces poisonous cardiac and maintain glycosidic compounds, so cattle avoid grazing ecological balance on it. 52. (a) Adaptations of parasite 3 Marks Questions • Loss of sense organs 47. Predation keeps prey population in check, helps to • Adhesive organs and sucker well developed maintain ecological balance and species diversity, it also acts as conduit for energy transfer. • Loss of digestive system 48. Interaction between two species in which both • Reproductive capacity is very high the interacting species are benefitted from each other. (b) Koel lays its eggs in the nest of a crow. Crow fails to identify koel’s eggs from its own due e.g. 1. Rhizobium: lives as symbiont within the to similar size and colour and incubates them root nodules of leguminous plants. Rhizobium as its own. fixes atmospheric nitrogen and root provides nutrients and habitat to bacterium. 53. Fig and wasp is an example of co-evolution. The female wasp uses the fruit for oviposition, e.g. 2. Mycorrhiza: interaction between fungus and uses seeds within the fruit for nourishing its roots of higher plants. The fungi absorbs minerals larvae, in turn the wasp pollinates the flowers from soil and plant provides photosynthetic of fig inflorescence. They both are obligatory to products to fungi. each other, fig can only get pollinated by none other than the partner wasp species. 49. Mycorrhizae: Mutualism 54. (i) Parasitism (ii) Mutualism An association between fungi like Glomus with the roots of higher plants like Pinus. The fungi (iii) Commensalism (iv) Mutualism absorbs minerals from soil and plant provides photosynthetic products to fungi. (v) Commensalism (vi) Competition Cattle egret and cattle: Commensalism 55. (a) A-unlimited food and space B-Limited food and space Cattle stirs up and flushes out insects from the vegetation on which the cattle egret feeds, cattle (b) Curve A is neither harmed nor benefitted. (c) The dotted line represents the carrying 50. Mutualism: Two interacting organisms where capacity. When a population grows to its both are benefitted, e.g. Lichens: algae and maximum, and reaches at this point, the fungi are mutually benefitted, algae provide food resources become limited and beyond which habitat to fungi which in turn absorb nutrients no further growth is possible. for algae. 56. Age pyramids for expanding human population. Parasitism: Two interacting organisms where one gets benefited and other gets harmed, e.g. Post-reproductive tapeworm in human alimentary canal. Reproductive Commensalism: Two interacting species where one is benefitted and the other is neither harmed Pre-reproductive nor benefitted, e.g. Orchid growing on a mango plant as an epiphyte, orchid gets habitat, mango Expanding remains unaffected. Expanding age pyramid: the pre-reproductive 51. (a) Thorns, spines are the morphological defence. individuals are more in number than any other Chemicals such as nicotine, caffeine, age group, thus when they will reproduce, quinine are chemical defence. the population size will increase, hence called expanding population. Thus in growing population birth rate is high. 57. (a) By measuring the size of a population we can predict (i) Status of the population in a habitat and size in future whether increases or decreases. Organisms and Populations  277

(ii) What will be the effect of competition found growing on hedge plants, has lost among different species? its chlorophyll and leaves in the course of evolution. It derives its nutrition from the (iii) Impact of predators or pesticides. host plant which it parasitizes. (b) Example: Banyan tree and grasses on 63. Predation keeps prey population in check, helps to grassland. maintain ecological balance and species diversity, it also acts as conduit for energy transfer. When 1 banyan tree is compared with 100 grass plants, the population of banyan in terms of 64. (a) A is exponential growth curve or J-shaped number is very much low as compared to that growth curve. of grass but percentage cover or biomass of the banyan is much larger in comparison to 100 grass B is logistic growth curve or S-shaped. plants. Thus, the percentage cover or biomass is a more meaningful measure of population size in (b) Logistic growth curve (B) is considered more this case. realistic because unlimited resources are not available in an ecosystem or in a habitat. 58. (a) Birth rate is expressed as the number of births per 1,000 individuals of a population (c) K stands for carrying capacity. per year. For example, in a pond there were (d) N symbolises population density. 80 lotus plants and 40 more were added in a 65. (a) A is exponential growth curve. year. Then the birth rate of the population B is logistic growth curve. will be 40/80= 0.5 plants per year. (b) A = When resources are unlimited. (b) Sex ratio, population density, age distribution, B = When resources are limited. population growth. (Any two) (c) dN = rN K − N 66. dt  K  59. (a) Death rate is expressed as the number of deaths per 1,000 individuals of a population per year. For example, on a tree 200 birds were living and 40 of them died in a year. Population density (N) Then the death rate of the population will be K 40/200 = 0.5 birds per year. ddNt = rN K–N K (b) Sex ratio, age distribution, population density, b population growth. (Any two) 60. The curve-'A' will be obtained. Forest have unlimited food for herbivores hence the resources are unlimited. The population of herbivores will Time (t) grow exponentially as there will be no predator A population growing in a habitat with limited resources shows initially a lag phase, followed to keep check on the population. by phases of acceleration and deceleration and finally an asymptote, when the population 61. (a) Population density can be counted by physical density reaches the carrying capacity. counting, percent cover or total biomass, from relative density such as bacteria in water, counting pug marks or counting faecal pellets 67. (a) Parasitic (b) Commensalism (c) Competition (d) Mutualism of an animal in forest. 68. (a) A - Expanding B - Stable  C - Declining (b) It will let us know the status of habitat, (b) Pyramid B (Stable) is ideal for human whether competition for survival exists or not, whether population is increasing or declining. population because it will be helpful for 62. • Commensalism: the two individuals closely planning future welfare strategies. It will also interact with each other where one gets help in better survival of human population. benefited but other is neither harmed nor 5 Marks Questions benefitted, e.g. An orchid growing as an 69. (a) Exponential growth and logistic growth epiphyte on a mango branch. Orchid gets habitat but mango plant remains unaffected. (a) Exponential Growth • Mutualism: The two individuals closely Curve dN = rN dt interact with each other where both of them gets benefit of each other, e.g. Lichens are Population density (N) K symbiotic association of fungi and algae. dN = rN K – N Fungi absorb nutrients and algae provide dt K photosynthetic product to lichens. (b) Logistic • Parasitism: The two individuals closely Growth interact with each other where one gets Curve benefited and the other is harmed, e.g. Cuscuta, a parasitic plant that is commonly Time (t) 278 Biology–12

(b) Exponential growth - food resources and space Where unlimited, N = population density at time t. r = Intrinsic rate of natural increase. Logistic growth - food resources and space K = carrying capacity. limited Population density (N) K (c) Exponential growth curve, the curve is not sustainable because the resources are ddNt = rN K–N limited and the growth cannot happen beyond K nature's carrying capacity. b 70. With increasing population, the strategies Time (t) should be planned to allocate resources in such a manner that each one gets equal opportunities 73. (a) Population can increase or decrease due to for the livelihood, this can be done by creating more job opportunities, infrastructural facilities following factors. to educate children and by investing more on medical facilities and transport facilities. Natality (B): Total number of births in given 71. (a) Population attributes: Birth rate and death period of time. rate, age pyramids. Mortality (D): Total number of deaths in (b) Population density: Number of individuals per unit area. given period of time. (i) Density measured by calculating biomass: Immigration (I): Number of individuals Example: In a plot under 200 Parthenium which migrate in a habitat to live. plant but single banyan tree with large canopy, the banyan tree density is Emigration (E): Number of individuals measured in terms of cover area or biomass. which leave the habitat. (ii) Indirect observation, e.g. number of fish If N is the population density at a given time caught per trap to measure density of fish in a lake. t, then population growth is given by (iii) Total count per unit area. Nt + 1 = Nt + [(B + I) – (D + E)] Example: no. of males living in a human (b) Population density can be counted by physical population of an area. counting, percent cover or total biomass, from 72. (a) The equation represents exponential growth. ‘r’ represents intrinsic rate of natural relative density such as bacteria in water, increase. counting pug marks or counting faecal pellets It helps us to assess impacts of any biotic or of an animal in forest. abiotic factor on population growth. 74. (a) J-shaped-Growth S-shaped-Growth (b) When a population is growing exp-onentially, Curve Curve there will be competition between individuals for resources and the theory of survival for the Resources are unlimited Resources are limited fittest will be applied. The population will not grow beyond its carrying capacity K. Growth is exponential Logistic Growth This represents the point where resources become As resources are Fittest individual will limited and the competition among individuals starts in terms of food and space. unlimited all individuals survive and reproduce survive and reproduce If we plot growth against time, we get sigmoid Growth Equation dN/ Growth Equation dN/ curve and is represented as: dt = rN (If explained) dt = rN (K – N/K) (If dN = rN K − N explained) dt  K  Note: Marks to be awarded only if the corresponding difference is written. (b) When resources are limited, Competition occurs between individuals, fittest will survive, who reproduce to leave more progeny. Organisms and Populations  279

Assertion & Reason Type Questions For question numbers 1-5: Two statements are Reason: Predators and parasites limit the given one labelled Assertion (A) and the other labelled population of their host species. Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. 3. Assertion: Cuscuta is an example of holoparasite. (a) Both Assertion and Reason are true and Reason Reason: Cuscuta does not depend on other plants is the correct explanation of Assertion. for nutrition requirements. 4. Assertion: Amensalism is a negative interaction (b) Both Assertion and Reason are true but Reason is NOT the correct explanation of Assertion. between two living individuals Reason: In amensalism, allochemics are secreted (c) Assertion is true but Reason is false. (d) Assertion is false and Reason is also false. by one individual. 1. Assertion: With increase in population size, 5. Assertion: Emigration is outward movement of environmental resistance tends to increase. some individuals from local population. Reason: Emigration is caused by occurrence of Reason: This is a nature’s way to check the expression of biotic potential. deficiencies and calamities. 2. Assertion: Predation and parasitism are 1. (a) Answers 5. (b) considered to be negative interactions. 2. (a) 3. (c) 4. (b) Case Based Questions Reason: They show mutualistic relationship. 1. In many species of fig trees, there is a tight one- (a) Both assertion and reason are true and to-one relationship with the pollinator species of wasp. It mean that a given fig species can be reason is the correct explanation of pollinated only but its 'partner' wasp species and assertion. not other species. The wasp pollinates the fig inflorescence while looking for suitable egg-laying (b) Both assertion and reason are true but sites. In return for the favour of pollination the reason is not the correct explanation of fig offers the wasp some of its developing seeds assertion. as food for the developing wasp larvae. (c) Assertion is true but reason is false. (i) The interaction between fig trees and wasp is an example of (d) Both assertion and reason are false. (a) mutualism (b) commensalism 2. Age sex structure of a population can be depicted in the form of a pyramid by plotting the (c) amensalism (d) parasitism. percentage of population of each sex in each age class. Two age sex pyramids are as follows. (ii) All the given interactions are similar to interaction between fig trees and wasp, except (a) plant and animal relation for pollination (b) association of algae and fungi in lichens (c) association of cattle egret and grazing cattle (d) association of fungi and roots of higher plants in mycorrhiza. (iii) In which of the following interactions both partners are adversely affected? (a) Parasitism (b) Mutualism (c) Competition (d) Predation (iv) In relationship between fig and wasp (a) one benefitted other harmed (b) both are benefitted (c) one benefitted other unaffected (d) one inhibited, other unaffected. (v) Assertion: Fig and wasp cannot complete their life cycle without each other. 280 Biology–12

(i) Which of the following is correct regarding (c) Exponential growth has two phases lag pyramid B? and log. (a) It represents stable population. (d) In logistic growth, population passes (b) It represents expanding population. well beyond the carrying capacity of (c) It represents declining population. ecosystem. (d) Both (a) and (b) (ii) Total number of individuals of a species per (ii) Which of the following equations correctly represents the exponential population growth unit time is called curve? (a) population size (a) dN/dt = rN (b) population density (c) demography (b) dN = rN  K − N (d) population dynamics. dt  K  (iii) Which of the following is correct regarding (c) Nt = Noert (d) Both (a) and (c) age sex pyramid A and B? (iii) Which of the following equations correctly (a) A represents the age sex pyramid of represents Verhulst-Pearl logistic growth? developed country. (a) dN = rN  K − N (b) dN = rN (b) B represents the age sex pyramid of dt  K  dt K developing country. (c) dN = N(K − N) (d) dN = r(K − N) (c) A represents rapidly growing population. dt K dt K (d) Both (a) and (b) (iv) A population with a large proportion of older (iv) The population growth is generally described individuals than younger ones will likely to by the following equation: (a) grow larger first and then decline dN = rN  K − N (b) continue to grow indefinitely dt  K  (c) decline (d) none of these What does ‘r’ represent in the given equation? (v) Assertion: Bell shaped age pyramid (a) Population density at time ‘t’ (b) Intrinsic rate of natural increase represents a stable population. (c) Carrying capacity (d) The base of natural logarithm Reason: In a stable population, proportion of (v) Study the population growth curves (A and individuals in reproductive age group is higher than the individuals in pre-reproductive age B) in the given graph and select the incorrect group. option. (a) Both assertion and reason are true and (a) Curve ‘A’ shows exponential growth, reason is the correct explanation of assertion. represented by equation dN = rN dt (b) Both assertion and reason are true but reason is not the correct explanation of (b) Curve ‘B’ shows logistic growth, represented assertion. by equation dN = rN  K − N (c) Assertion is true but reason is false. dt  K  (d) Both assertion and reason are false. 3. Growth of a population with time shows specific (c) exponential growth curve is considered as more realistic than the logistic growth and predictable patterns. Two types of growth curve. pattern of population are exponential and logistic growth. When resources in the habitat are (d) Curve ‘A’ can also be represented by unlimited each species has the ability to realise equation Nt = N0ert fully its innate potential to grow in number. Then the population grows in exponential fashion. When the resources are limited growth curve shows an initial slow rate and then it accelerates and finally slows giving the growth curve which is sigmoid. (i) Which of the following statement is incorrect? (a) Exponential growth occurs in organism such as lemmings. (b) Logistic growth is more realistic. Organisms and Populations  281

4. Ananya is a biologist, her research guide assigned (ii) Which of the following associations is an project, i.e., to determine the effect of intra- example of competitions? specific competition on the growth of sapling of Eucalyptus. For this, she designed an experiment (a) Cuscuta and hedge plant in which two sets of pots were used. In the first set (set A) only 1 sapling was planted per pot (b) Balanus and Cathamalus and in the other set (set B) 16 saplings were planted per pot. To check for the effect of intra- (c) Cactus and moth specific competition on allocation of resources, a decreasing amount of water was added to each (d) Orchid and mango set. The results have been graphically indicated. Which of the following conclusions can indicated (iii) If ‘+’ sign is assigned to beneficial interaction, as follows: ‘–’ sign to detrimental and 0 sign to neutral interaction, then the population interaction (i) Which of the following statements can be of competition refers to concluded from the given study? (a) More resources are allocated to the root (a) +, + (b) –, – during low water conditions. (c) +, – (d) +, 0 (b) Competition for water among individuals (iv) Intraspecific competition is more severe due of a population causes more root growth to as compared to individuals who are growing alone. (a) similar needs (c) Lesser leaves are formed under low water condition (b) similar adaptations (d) Root growth is higher in individual grown singly as compared to individuals in (c) common resources populations. (d) all of these. (v) Assertion: Two members of a competing species may co-exist. Reason: Different individuals of a species have different resource requirements. (a) Both assertion and reason are true and reason is the correct explanation of the assertion. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion. (c) Assertion is true, but reason is false. (d) Both assertion and reason are false. Ans. 1. (i) (a) (ii) (c) (iii) (c) (iv) (b) (v) (a) 2. (i) (b) (ii) (b) (iii) (d) (iv) (c) (v) (c) 3. (i) (d) (ii) (d) (iii) (a) (iv) (b) (v) (c) 4. (i) (b) (ii) (b) (iii) (b) (iv) (d) (v) (d) qqq 282 Biology–12

Topics Covered 12 Ecosystem 12.1 Ecosystem-Structure and Function 12.2 Productivity 12.3 Decomposition 12.4 Energy Flow 12.5 Ecological Pyramids 12.6 Ecosystem Services C hapter map ECOSYSTEM Structural Ecosystem Biotic Components Abiotic Components Autotrophic Heterotrophic (a) Climatic factors Components Components (b) Topography Consumers & (c) Organic and inorganic Producers Decomposers   substances Productivity of Energy flow Ecological Decomposition Ecosystem Food chain Pyramids Primary Food web Pyramid of (a) Leaching Productivity (b) Fragmentation Secondary number (c) Calabolism Productivity Pyramid of (d) Humification Community (e) Mineralization Productivity Biomass Pyramid of energy Ecosystem is the functional unit of nature where all An agricultural field is an example of man-made living organisms interact with each other and with terrestrial ecosystem. their surrounding physical environment. Aquatic ecosystem: Pond, lake, river, estuary • Ecosystem is divided into two basic categories: etc. are examples of aquatic ecosystems. An aquarium is an example of man-made aquatic Terrestrial ecosystem: Grassland, forest, desert ecosystem. etc. are the examples of terrestrial ecosystems. Topic 1. Ecosystem–Structure and Function • Physical structure and the characteristics of an • Species composition of an ecosystem is determined ecosystem is determined by interaction between by identification and counting of various plants and biotic and abiotic components. animals. 283

• Vertical distribution which occupies different levels Productivity is called stratification, e.g. in a forest ecosystem, Decomposition trees occupy top vertical strata, below which are Energy flow shrubs, herbs and grasses, respectively. Nutrient cycling • In an ecosystem, various components function as a unit in following aspects: Topic 2. Productivity photosynthesis is called Gross Primary Productivity (GPP). • Rate of biomass production is called productivity • Respiration utilizes most of the gross primary and is expressed in terms of g–2 yr–1 or kcal m–2 yr–1. productivity, the left is called Net Primary Productivity (NPP). • Amount of biomass produced per unit area over a GPP–R = NPP certain period of time by plants during photosynthesis is called primary productivity and is expressed in the • Rate of formation of new organic matter by consumers terms of weight (g–2) or energy (kcal m–2). is called Secondary Productivity (SP). • Rate of production of organic matter during Topic 3. Decomposition carbon dioxide, water and nutrients. It is done by decomposers. • Decomposition is a process of breakdown of complex organic matter into inorganic substances such as • Raw material for decomposition is detritus which is dead remains of plants and animals. A tree grows in the soil Some are eaten by insects and other animals. Nutrients and energy enter food web. A green leaf falls to the ground Leaves partially consumed by decomposers such as fungi and bacteria. They begin to lose form and become litter. Some nutrients leach into soil by chemical action Further decomposition by earthworms. bacteria, soil, mites, fungi, etc. Organic rich soil Diagrammatic Representation of decomposition cycle in a terrestrial ecosystem. • Decomposition occurs in the following steps: The water soluble inorganic nutrients go down Detritivores breaks detritus into smaller particles with water and get precipitated as unavailable and the process is called fragmentation. salts. This process is called leaching. 284 Biology–12

Rest of the detritus is broken down into simpler • Process of decomposition depends upon various organic substances by the action of bacteria and fungi. This is called catabolism. factors like presence of oxygen, temperature, pH of A dark coloured amorphous substance called soil, humidity etc. humus is formed and accumulated in the soil. This is called humification. Humus is reservoir If detritus is lignin and chitin rich, the rate of of nutrients. decomposition is slower and if detritus is nitrogen and water-soluble substances rich, the rate of Humus is degraded by microbes and inorganic decomposition is faster. nutrients are released in the soil. This is called mineralization. Decomposition will not happen if there are anaerobic conditions, lower temperature and less humidity. Topic 4. Energy Flow and bacteria. The decomposers secrete digestive enzymes and break down dead and waste material • Main source of energy is solar energy. into simple, inorganic material. • Photosynthetically active radiations (PAR) are the Dead Earthworm Bird solar rays which reach on the surface of earth and leaf is 50% of total solar radiations. • In aquatic ecosystem, GFC is responsible for major • O n l y 2 % o f P A R i s t r a p p e d b y p l a n t s f o r energy transfer. photosynthesis. Thus plants are called producers. • In terrestrial ecosystem, DFC is responsible for • The energy is passed into ecosystem by two ways: considerable fraction of energy transfer. Grazing food chain (GFC), here the plants are • In natural ecosystem, many food chains are eaten by primary consumers which are eaten by interconnected with each other, thus forming food secondary consumers, they in turn become food for web. tertiary consumers. Grass Goat Lion • Specific place occupied by any living organism in a food chain is called trophic level. Producers are at (Producer) (Primary (Secondary first trophic level, primary consumers are at second Consumer) Consumer) trophic level and secondary consumers are at third trophic level. Detritus food chain (DFC), when any organism dies, the energy is passed to decomposers like fungi Tertiary consumer Examples Man, lion Fourth trophic level (Top Carnivore) Secondary consumer Third trophic level Birds, fishes, wolf (Carnivore) Primary consumer Second trophic level Zooplankton, (Herbivore) grasshopper and cow Primary producer First trophic level Phytoplankton, (Plants) grass, trees Diagrammatic Representation of trophic levels in an ecosystem • Amount of energy decreases at each trophic level, only 10% of total energy is passed to next trophic thus restricting the number of trophic levels in level. Rest is lost as respiration and heat. GFC. The transfer of energy follows 10% law, i.e. Ecosystem  285

Heat First trophic Second trophic level Third trophic level Fourth trophic level producers primary consumers secondary consumers level tertiary (plants) (Herbivores) (carnivores) consumers Sun Heat Heat (top carnivores) Heat Heat Heat Heat Heat Energy Flow through different trophic levels • At any given time, the amount of living material present is called standing crop which is measured as biomass or number in a unit area. Topic 5. Ecological Pyramids tree ecosystem. Large number of insects live on a single big tree. • Ecological pyramids are the representation of the relationship of food or energy at different trophic • Ecological pyramids have some limitations: levels. These can be represented for energy, number and biomass. Same species if occupies more than one trophic level is not considered. • Pyramid of energy is always upright, as energy decreases in each higher trophic level. It takes in to consideration only a simple food chain which practically does not exist in nature. • Pyramid of biomass is upright in most of the ecosystems. In oceans, the pyramid of biomass is Food web is not considered inverted. • Saprophytes have no place in such pyramids which • Pyramid of number is upright when we study a play very important role in nutrient cycling. Topic 6. Ecosystem Services Also provides aesthetic, cultural and spiritual values. Benefits or products derived from nature are called ecosystem services. Robert Constanza and his colleagues tried to put price tags on these essential services. Minimum price • A forest is a good example of ecosystem services. which is estimated for these ecosystem services for • Forest: a year is US $ 33 trillion which is nearly twice the value of the global gross national product GNP which Gives us pure air and water is (US $ 18 trillion). And we take all these services as Helps in mitigating droughts and flood granted as nature provides us with all these for free. Provides fertile soils Is a habitat to wildlife Maintains biodiversity EXERCISE I. Multiple Choice Questions 2. The process of mineralisation by micro organisms helps in the release of: 1. Decomposers like fungi and bacteria are: (i) autotrophs (ii) heterotrophs (a) inorganic nutrients from humus (b) both organic and inorganic nutrients from (iii) saprotrophs (iv) chemo-autotrophs. detritus Choose the correct answer: (c) organic nutrients from humus (d) inorganic nutrients from detritus and (a) (i) and (iii), (b) (i) and (iv) formation of humus. (c) (ii) and (iii), (d) (i) and (ii) 286 Biology–12

3. Productivity is the rate of production of biomass 14. The sequence of communities of primary expressed in terms of: succession in water is: (i) (kcal m–3) yr–1 (ii) g–2 yr–1 (a) p h y t o p l a n k t o n , s e d g e s , f r e e - f l o a t i n g (iii) g–1 yr–1 (iv) (kcal m–2) yr–1 hydrophytes, rooted hydrophytes, grasses and trees. (a) (ii), (b) (iii), (b) phytoplankton, free-floating hydrophytes, (c) (ii) and (iv), (d) (i) and (iii) rooted hydrophytes, sedges, grasses and trees. 4. An inverted pyramid of biomass can be found in (c) f r e e - f l o a t i n g h y d r o p h y t e s , s e d g e s , which ecosystem? phytoplankton, rooted hydrophytes, grasses and trees. (a) Forest (b) Marine (c) Grassland (d) Tundra (d) p h y t o p l a n k t o n , r o o t e d s u b m e r g e d hydrophytes, floating hydrophytes, reed 5. Which of the following is not a producer? swamp, sedges, meadow and trees. (a) Spirogyra (b) Agaricus (c) Volvox (d) Nostoc 15. T h e r e s e r v o i r f o r t h e g a s e o u s t y p e o f biogeochemical cycle exists in 6. Which of the following ecosystems is most productive in terms of net primary production? (a) stratosphere (b) atmosphere (a) Deserts (c) ionosphere (d) lithosphere (b) Tropical rain forests II. Fill in the Blanks (c) Oceans 1. Composition of the atmosphere is quite uniform upto a height of ____ kilometres. (d) Estuaries 7. Pyramid of numbers is: 2. Nutrient cycles are also known as ______ . (a) Always upright 3. Dead plant parts and animal remains are called (b) Always inverted _____ . (c) Either upright or inverted 4. ____ is the rate of formation of new organic matter by consumers. (d) Neither upright nor inverted 8. Approximately how much of the solar energy 5. Vertical distribution of different species occupying that falls on the leaves of a plant is converted to different levels is called _____ . chemical energy by photosynthesis? III. True or False (a) Less than 1% (b) 2-10% 1. Tropical forest is found in Rajasthan in India. 2. Pyramids of numbers deal with the number of (c) 30% (d) 50% individuals in a community. 9. Among the following, where do you think the process of decomposition would be the fastest? 3. The maximum biomass occurs in temperate (a) Tropical rain forest forests. (b) Antarctic 4. Earth is an open system regarding matter. 5. Lions and wolves occupy the same trophic level. (c) Dry arid region (d) Alpine region I V. Match the items in Column I with those of Column II: 10. How much of the net primary productivity of a terrestrial ecosystem is eaten and digested by herbivores? Column I Column II (i) Primary productivity A. Bacteria, Fungi (a) 1% (b) 10% (ii) Natural ecosystem B. Consumers (iii) Desert C. Lake (c) 40% (d) 90% (iv) Decomposers D. Biome (v) Secondary productivity E. Producers 11. During the process of ecological succession the F. Forest changes that take place in communities are: (a) Orderly and sequential (b) Random (c) Very quick (d) Not influenced by the physical environment. 1 Mark Questions 1. Write the difference between net primary 12. Climax community is in a state of: (a) non-equilibrium (b) equilibrium productivity and gross primary productivity.  [AIl India 2011] (c) disorder (d) constant change. 2. “Man can be a primary as well as a secondary 13. Among the following biogeochemical cycles which consumer.” Justify this statement. one does not have losses due to respiration?  [Foreign 2015 C] (a) Phosphorus (b) Nitrogen (c) Sulphur (d) All of the above Ecosystem  287

3. How is ‘stratification’ represented in a forest 22. Describe how do oxygen and chemical composition of ecosystem? [Delhi 2014] detritus control decomposition. [Delhi 2011] 23. Differentiate between a Detritivore and 4. What does ‘R’ represent in the given equation for decomposer giving an example. [Delhi 2008] productivity in an ecosystem? OR        GPP – R = NPP. [Delhi 2014] How does a detritivore differ from a decomposer? 5. Write the equation that helps in deriving the net primary productivity of an ecosystem. Explain with an example each. [Delhi 2015 C] 24. Name the type of food chains responsible for the  [Delhi 2013] flow of larger fraction of energy in an aquatic and 6. How is the net primary productivity of an a terrestial ecosystem respectively. Mention one ecosystem derived? [All India 2012 C] difference between the two food chains. 7. How is net primary productivity different from  [Delhi 2010] 25. Why are herbivores considered similar to gross primary productivity? [All India 2012 C] predators in the ecological context? Explain. 8. What is secondary productivity? [Delhi 2009 C]  [All India 2010] 9. All the primary productivity is not avail-able to 26. Explain with the help of two examples, how the a herbivore. Give one reason. [Delhi 2009 C] pyramid of number and the pyramid of biomass 10. What is net primary productivity of an ecosystem? can look inverted. [Foreign 2011]  [Delhi 2008 C] 27. Explain ‘standing crop’ in an ecosystem. Draw a 11. What is a detritus food chain made up of? How pyramid of biomass when a small standing crop do they meet their energy and nutritional of phytoplanktons supports and large standing requirements? [All India 2013] crop of zooplanktons in the sea. [Delhi 2010 C] 12. State what does standing crop of a trophic level 28. Explain the response of all communities of represent. [All India 2013] environment over time. [All India 2010] 13. Name the dominant producers in a deep aquatic 3 Marks Questions ecosystem. What other name could you give to a 29. Justify the importance of decomposers in an primary consumer. [Delhi 2007] ecosystem.  [Foreign 2015 C] 14. What is the starting point of a detritus food 30. Why is earthworm considered a farmer’s friend? chain? [Delhi 2007] Explain humification and miner-alization 15. Mention any two reasons why the primary occurring in a decomposition cycle. productivity varies in different types of  [Foreign 2015 C] ecosystems? [All India 2014 C] 31. How does a detritivore differ from a decomposer? 16. Why are green algae not likely to be found in the Explain with an example each. [Delhi 2015 C] deepest strata of the ocean? [All India 2014 C] 32. Draw a pyramid of biomass and pyramid of 2 Marks Questions energy in sea. Give your comments on the type 17. State the difference between the first trophic level of pyramids drawn. [Foreign 2016] of detritus food chain and grazing food chain. 33. Construct an ideal pyramid of energy when  [All India 2008] 1,000,000 joules of sunlight is available. Label 18. Identify the type of given ecological pyramid and all its trophic levels. [Delhi 2009] give one example each of pyramid of number and pyramid of biomass in such cases. 34. “In a food-chain, a trophic level represents a functional level, not a species.” Explain.  [Delhi 2016] 35. (a) What is primary productivity? Why does it vary in different types of ecosystems?     [AlI India 2011] (b) State the relation between gross and net primary productivity [Delhi 2014] 19. How are productivity, gross productivity, net primary productivity and secondary productivity 36. Why is earthworm considered a farmer’s friend? Explain humification and mineralisation interrelated? [Delhi 2015] 20. What does secondary productivity in an occurring in a decomposition cycle. ecosystem indicate? List any two factors by which  [Foreign 2015] productivity is limited in aquatic ecosystems. 37. ‘‘It is possible that a species may occupy more than one trophic level in an ecosystem at the  [Delhi 2007] 21. How does the dead organic matter get decomposed same time’’. Explain with the help of one example. in nature? Explain. [All India 2012 C]  [All India 2008 C, 2013] 288 Biology–12

38. Construct labelled grazing and detritus food (b) Explain the conditions affecting the rate of chain with minimum 3 trophic levels each. decomposition. [AI India 2009 C] 47. ‘‘It is often said that the pyramid of energy is  [All India 2013 C] 39. Discuss the relationship between detritus food always upright. On the other hand, the pyramid chain and grazing food chain in a terrestrial of biomass can be both upright and inverted.’’ ecosystem. [All India 2012 C] Explain with the help of example and sketches. 40. Differentiate between two different types of  [All India 2015] pyramids of biomass with the help of one example 48. (a) With suitable examples, explain the energy of each. [All India 2013] flow through different trophic levels. What 41. Construct a pyramid of biomass starting with does each bar in this pyramid represent? phytoplanktons. Label 3 trophic levels. Is the (b) Write any two limitation of ecological pyramid upright or inverted. Why? pyramids. [AI India 2014 C] 49. (a) Draw an ideal pyramid of energy upto four  [All India 2009] 42. Describe the inter-relationship between trophic levels where 10,00,000J are available from sunlight to the primary producer. productivity, gross primary productivity and Indicate the amount of energy available at net productivity. [All India 2017] each trophic level. 5 Marks Questions (b) Why is pyramid of energy always upright? 43. (a) Explain primary productivity and the factors Explain. that influence it. (c) Mention the limitations of an ecolo-gical (b) Describe how do oxygen and chemical pyramid [All India 2012 C] composition of detritus control decomposition. 50. (a) Draw a ‘pyramid of numbers’ of a situation  [Delhi 2011] where a large population of insects feed upon 44. (a) Taking an example of a small pond, explain a very big tree. The insects in turn, are eaten how the four components of an ecosystem by small birds which in turn are fed upon by function as a unit. big birds. (b) Differentiate giving reason, between the (b) Name the type of food chain that exists in a pyramid of biomass of the above situation and pond. [All India 2016] the pyramid of numbers that you have drawn. 45. How is detritus decomposed step-by-step by  [Delhi 2012] different agents and made available as nutrients 51. (a) Explain the significance of ecological pyramid to the plants? Explain. [Delhi 2013 C] with the help of an example. OR (b) Why are the pyramids referred to as ‘upright’ Explain the different steps involved in the process or ‘inverted’? Explain. [All India 2012] of decomposition of detritus [Delhi 2011 C] 52. Describe the advantage for keeping the ecosystems OR healthy. [All India 2015] Describe the process of decomposition of detritus 53. (a) What is an ecological pyramid? Compare the under the following heads: Fragmentation, leaching, pyramids of energy, biomass and numbers. catabolism humification and mineralisation. (b) Write any two limitations of ecological [Delhi 2010] pyramids. [All India 2017] OR 54. (a) What is a trophic level in an ecosystem? What List the different steps and state their role in the is ‘standing crop’ with reference to it? process of decomposition in an ecosystem. (b) Explain the role of the ‘first trophic level’ in  [Delhi 2008 C] an ecosystem. 46. (a) Describe the events during humi-fication and (c) How is the detritus food chain connected with mineralisation during decomposition in the the grazing food chain in a natural ecosystem? soil.  [CBSE 2018] Answers I. Multiple Choice Questions 5. stratification 1. (c) 2. (a) 3. (c) 4. (b) 5. (b) III. True or False 6. (b) 7. (c) 8. (b) 9. (a) 10. (b) 1. True 2. False 3. False 4. False 5. True 11. (a) 12. (b) 13. (d) 14. (d) 15. (b) IV. M atch the items of Column I with those of II. Fill in the Blanks Column II: 1. 80 2. biogeochemical (i) → E, (ii) → C, F, (iii) → D, (iv) → A, (v) → B 3. detritus 4. secondary productivity Ecosystem  289

1 Mark Questions 18. The pyramid is of inverted type. Inverted pyramid of biomass can be seen in water 1. Gross primary productivity (GPP) is the rate of production of organic matter during body. photosynthesis. Fishes Net primary productivity (NPP) is the available Zooplanktons biomass after respiratory losses. This is represented as GPP – R = NPP Phytoplanktons 2. If man takes vegetarian diet, he is a primary Inverted pyramid of number can be seen in a consumer and if he takes non vegetarian diet, he parasitic food chain. is a secondary consumer. 3. Stratification in a forest ecosystem is represented Hyperparasites as trees occupying top vertical strata, below which are shrubs, herbs and grasses form middle Parasites and bottom strata, respectively. 4. 'R' represents the energy loss due to respiration. Birds 5. GPP – R = NPP 6. Refer answer no. 5. Tree 7. Gross primary productivity (GPP) is the rate of production of organic matter during 19. Productivity is rate of biomass production and photosynthesis. net primary productivity is the biomass available Net primary productivity (NPP) is the available biomass after respiratory losses. to the consumers after respiratory losses. The This is represented as GPP − R = NPP 8. Secondary productivity is rate of formation of new relationship between two can be given as: organic matter by consumers. 9. This is because there is some loss due to GPP – R = NPP. respiration. 20. Organic matter formation in consumers is 10. The amount of biomass or energy left in a secondary productivity. Light, temperature and producer after respiratory losses is called net primary productivity. This is represented as NPP availability of nutrients (any two). = GPP − R 21. Decomposition occurs in following steps: fragmentation, leaching, catabolism, 11. Detritus food chain is made up of decomposers which are heterotrophic organisms, mainly fungi humification and mineralisation. Raw material and bacteria who meet their energy and nutrient for decomposition is detritus which is dead requirements by degrading dead organic matter remains of plants and animals. Detritivores or detritus. break down detritus into small fragments, the 12. Mass of living material at a particular time is water soluble nutrients are leached into the called as the standing crop. soil. Rest is broken down further and humus is 13. Phytoplankton, algae and higher plants. Herbivores. formed. The minerals are released for reuse as 14. Dead remains of organic matter. the raw material by the plants. 15. Difference in productivity is due to 22. If detritus is lignin and chitin rich, the rate of (i) Type of vegetation decomposition is slower and if detritus is nitrogen (ii) A v a i l a b i l i t y o f n u t r i e n t s a n d o t h e r and water-soluble substances rich, the rate of environmental factors. decomposition is faster. 16. Light is the limiting factors in deep oceans, it cannot penetrate deep in water. Without light Decomposition will not happen if there are anaerobic conditions, lower temperature and less there will be no photosynthesis, thus algae do humidity. not survive there. 23. Detritivore Decomposer 2 Marks Questions Detritivore is an Decomposer is an 17. In detritus food chain, the first trophic level is organism that organism which dead and decaying organic matter and in grazing breaks down further degrades detritus into detritus into food chain, the first trophic level is autotrophic smaller fragments. simpler organic plants. Example: substances Example: earthworm bacteria and fungi 24. Detritus food chain in aquatic system and grazing food chain in terrestrial ecosystem are responsible for flow of larger fraction of energy. G r a z i n g F o o d C h a i n ( G F C ) s t a r t s w i t h photosynthetic plants and Detritus Food Chain (DFC) begins with dead organic matter and decomposers. 290 Biology–12

25. Predators feed on other organisms and obtain 28. All communities reach a climax commu-nity energy. Similarly herbivores also do the same. over time which is a stable and self sustainable community. All successions whether taking place 26. Pyramid of biomass in a sea ecosystem: in water or on land, proceed to a similar climax Phytoplankton with small biomass are eaten by community – the mesic. small fishes (more biomass than phytoplankton), 3 Marks Questions which in turn are eaten by large fishes (very high biomass) 29. Decomposers act as natural scavengers, they help to break down dead complex organic matter Carnivores into simple inorganic materials and thus help in recycling of nutrients. Herbivores 30. Earthworm helps in breaking down of complex Producers organic matter of detritus and it also helps in loosening of the soil. Pyramid of Biomass Pyramid of number in a tree ecosystem: Humification leads to amorphous solid called On a single tree, there live many birds. On the humus which decomposes slowly and is a reservoir of nutrients. birds in turn live many parasites. Each parasite too is parasitized by many hyperparasites. Humus is further degraded by microbes and nutrients are released into soil. This is called Hyperparasites mineralization. Parasites 31. Detritivore Decomposer D e t r i t i v o r e f e e d s Degrades dead organic on dead plant and matter by secreting animal remains, and enzymes, the organic breaks them into matter releases small fragments, e.g. inorganic nutrients, e.g. earthworm bacteria and fungi 32. Pyramid of biomass in sea, it is always inverted PC 21 PP 4 Here producers are phytoplanktons and their biomass is 4 kg m–2 and primary consumers are zooplanktons and their biomass is 21 kg m–2. Pyramid of energy in sea is always upright. Herbivores TC 10 J Producers SC 100 J Pyramid of Number PC 1000 J 27. Mass of living material at a particular time is PP 10,000 J called as the standing crop. 1,000,000 J of Sunlight PC 21 PP 4 The energy decreases at each successive trophic level due to respiratory losses. PP: Primary Producers; PC: Primary Consumers; numbers: 4 and 21 are biomass expressed in dry 33. Refer answer no. 32. weight (kg m–2) 34. Position of a species in any trophic level is determined by the mode of nutrition in a particular food chain. A given species may occupy more than one trophic levels in the same ecosystem but in different food chains at the same time. e.g. Man can be at second trophic level i.e. primary consumer if he takes a vegetarian diet but if he takes a non- vegetarian diet, he occupies third trophic level. Ecosystem  291

35. (a) The amount of biomass or energy produced 41. T3 Fishes per unit area in a given time per year by plants during photosynthesis is primary T2 Zooplanktons productivity. It depends upon-plant species inhabiting a particular area, environmental T1 Phytoplanktons factors, availability of nutrients and photosynthetic capacity of plants which vary The pyramid is inverted because the biomass in different types of ecosystems. of fishes is much more than that of the (b) GPP–R = NPP. 36. Earthworm is considered as farmer's friend phytoplanktons. 42. Productivity is the rate of biomass production per because it is a detritivore which breaks down the detritus into smaller fragments. Then bacteria unit area over a period of time, and fungi act faster on smaller fragments and Gross primary productivity is the rate of production are degraded into simpler organic matter. of organic matter during photosynthesis in an ecosystem, A dark coloured amorphous substance called Net productivity is the gross primary productivity minus respiration losses (R) humus is formed and accumulated in the soil. 5 Marks Questions This is called humification. Humus is reservoir 43. (a) Primary productivity is the amount of biomass of nutrients. produced per unit area over a certain period of time by a plant during photosynthesis. Humus is degraded by microbes and inorganic Factors which influence the primary nutrients are released in the soil. This is called productivity are: availability of nutrients, light, optimum temperature, type of plant mineralization. species of an area, photosynthetic capacity of plants. 37. Let us take an example of an omnivore animal, a squirrel. When it eats seeds, fruits or nuts, acts (b) Presence of oxygen increases rate of decomposition and if detritus is rich in as primary consumer and occupies second trophic chitin and lignin, the decomposition rate is slower whereas if it is nitrogen rich, the level. When it eats insects it acts as secondary decomposition rate is higher. consumer and occupies third trophic level. Thus 44. (a) Four components of an ecosystem are productivity, decomposition, energy flow and omnivores occupies more than one trophic level nutrient cycling. In a pond ecosystem it can be explained as follows: in the same ecosystem. (i) Productivity: Phytoplanktons, algae in 38. Grazing food chain and detritus food chain littoral zone, floating or submerged plants fix carbon-dioxide into carbohydrates by Tertiary Hawk Nematode photosynthesis. This is primary productivity. Consumer (ii) Decomposition: Fungi and bacteria act as Secondary Bird protozoa decomposers in water which break down the Consumer dead organic matter into simpler compounds. bacteria/ Primary Larvae fungi (iii) Energy flow: In aquatic ecosystem the flow Consumer of energy from first trophic level to next higher one takes place by grazing food chain. Primary Cabbage detritus It is unidirectional movement and is also Producer dissipated in environment as respiratory losses. trophic levels Grazing food Detritus food (iv) Nutrient cycle: Minerals are released chain chain from dead organic matter by the process of mineralisation. These minerals are reused 39. In terrestrial system, larger fraction of energy by autotrophs. flows through detritus food chain. Detritus food (b) Grazing food chain chain may be connected with the grazing food 45. Decomposition of detritus occurs in the following chain at some levels: some of the organisms steps: of DFC are prey to the GFC animals, and (i) Detritivores break detritus into smaller in a natural ecosystem, some animals like particles and the process is called cockroaches, crows, etc., are omnivores. fragmentation. 40. In upright pyramid of biomass the biomass of (ii) The water soluble inorganic nutrients go producers is more than that of consumers which in turn is more than that of next consumer. down with water and get precipitated as Example: plants → deer → lion In inverted pyramid of biomass, the biomass of producers is less than that of consumers. 292 Biology–12

unavailable salts. This process is called 48. (a) Refer answer no. 46. Pyramid of Energy leaching. (b) Ecological Pyramids only take simple food (iii) Rest of the detritus is broken down into simpler organic substances by the action of chains and food web into consideration. bacteria and fungi. This is called catabolism. Saprophytes have no place in pyramids. (iv) A dark coloured amorphous substance called 49. (a) Refer answer no. 32. humus is formed and accumulated in the (b) Pyramid of energy is always upright as energy soil. This is called humification. Humus is decreases in each higher trophic level. reservoir of nutrients. (c) Refer answer no. 47 (b). (v) Humus is degraded by microbes and inorganic 50. (a) Pyramid of number nutrients are released in soil. This is called mineralization. Big Birds 46. (a) Refer answer no. 44. (b) Refer answer no. 22 Birds 47. Energy decreases at each successive trophic level. Insects This is shown by the food chain given below: Plants → rat → snake → hawk PP Tree The pyramid of energy depicting the flow of (b) Reason: The tree is single but has large energy in the given food chain is represented as: biomass. Biomass does not depend upon number so both Pyramids are different. Big Birds Birds Insects Tree TC 10 J 51. (a) Ecological pyramid are the fund-amental and simple basis to compare different ecosystems SC 100 J and any change within them. It expresses the relationship between the organisms at PC 1000 J different trophic levels with reference to their number, energy and biomass. PP 10,000 J e.g. Pyramid of energy is always upright. 1,000,000 J of Sunlight In the above figure, it is clear that the amount of Trophic level Dry weight (kg m–2) energy decreases in each successive trophic level. From 10,000 J at producers' level, it remains only TC 10 J 10 J at tertiary consumers' level. Only 10% of energy is passed to next trophic level in all food SC 100 J chains. Thus it is clear that pyramid of energy is always upright. PC 1000 J Pyramid of biomass can be inverted: In an PP 10,000 J aquatic ecosystem, the biomass of phytoplanktons 1,000,000 J of Sunlight is much less than that of zooplanktons that feed (b) In upright pyramids, the base is broader than upon phytoplanktons. the successive levels and gradually narrows down towards apex. Here the producers Trophic level Dry weight (kg m–2) are more in number or in terms of energy. Example: phytoplanktons → zooplanktons → PC 21 small fish → large fish. PP 4 In inverted pyramids, the producers are always small in number than the consumers. Pyramid of biomass can also be upright: In a Example: many birds live on tree, many terrestrial ecosystem, rabbit eats grass, fox eats insects live on each bird and each bird has many parasites on its bodies. rabbit and tiger eats fox. The biomass in terms of 52. A healthy ecosystem provides us with the dry weight decreases with each successive trophic following benefits: level.  We get pure air and water from forests  Helps in mitigating droughts and flood Trophic level Dry weight (kg m–2)  Helps in maintaining nutrient cycling  Provides fertile soils TC 10 J  Is a habitat to wildlife  Maintains biodiversity SC 100 J  Helps bee and other insects pollinate crops PC 1000 J PP 10,000 J 1,000,000 J of Sunlight Ecosystem  293

 Acts as reservoir of carbon • Saprophytes are not given any place in such  Also provides aesthetic, cultural and spiritual pyramids. values. 54. (a) Trophic level: Based on the source of their 53. (a) Graphical representation of the relationship nutrition or food, organisms occupy a specific place in the food chain that is known as their among the organisms at different trophic trophic level. Each trophic level has a certain levels. mass of living material at a particular time called as the Standing crop. Pyramid of Pyramid of Pyramid of Energy Bio Mass Numbers (b) The first trophic level belongs to producers; they trap solar energy, assimilate it and pass Shows transfer Shows transfer of Pyramid of Num- it to the next trophic level. of Energy from amount of food/ bers shows num- one tropic level to biomass from one bers of organism (c) Detritus food chain may be connected with other tropic level to at seach tropic the Grazing food chain at some levels; some other level. of the organisms of DFC are prey to the GFC animals and in a natural ecosystem, some Always upright Mostly upright Mostly upright animals like cockroaches, crows etc. are but can be in- can be inverted omnivores. verted (b) Limitations are • It does not take into account the same species at different trophic levels Assertion & Reason Type Questions For question numbers 1-7: Two statements are given 4. Assertion (A): Decomposition is a process one labelled Assertion (A) and the other labelled Reason of breakdown of complex organic matter into (R). Select the correct answer to these questions from inorganic matters. the codes (a), (b), (c) and (d) as given below. (a) Both Assertion and Reason are true and Reason Reason (R): Raw material for decomposition is detritus. is the correct explanation of Assertion. 5. A s s e r t i o n ( A ) : Decomposition depends (b) Both Assertion and Reason are true but Reason upon various factors like presence of oxygen, is NOT the correct explanation of Assertion. temperature, humidity etc. (c) Assertion is true but Reason is false. Reason (R): Decomposition will not happen if (d) Assertion is false and Reason is also false. there are anaerobic conditions, lower temperature 1. Assertion (A): Pyramid of energy is upright. and less humidity. Reason (R): During the energy transfer at 6. Assertion (A): ‘Specific place’ occupied by any successive trophic levels from producers there living organism in a food chain is called ‘trophic will be a gradual decrease. level’. 2. Assertion (A): In forest ecosystem, the pyramid Reason (R): Primary consumers are at first of number is spindle shaped. trophic level. Reason (R): Tropical level of the pyramid 7. Assertion (A): Photosynthetically Active occupies large tree which are maximum in Radiations (PAR) are the solar rays, which reach number. on the surface of earth. 3. Assertion (A): Pond, lake, river etc. are aquatic Reason (R): Only 5% of PAR is trapped by plants ecosystems. for photosynthesis. Reason (R): ‘Aquarium’ is an example of man- 1. (a) Answers 5. (a) made aquatic ecosystem. 6. (c) 2. (c) 3. (b) 4. (b) 7. (c) Case Based Questions plants, animals and their excreta. This type of food chain is present in all ecosystems. The 1. Detritus food chain is a type of food chain which transfer of energy from the dead organic matter, begins with dead organic matter which is an is transferred through a series of organisms important source of energy. A large amount of organic matter is derived from the dead 294 Biology–12

called detritus consumers (detritivores) – small the producers. In final trophic lnevueml b(Te4r),thtearntiathrye consumers (lion) are lesser in carnivores – large (top) carnivores with repeated eating and being eaten respectively. This is called secondary consumer (T3) (fox and snake) (i) The following diagram represents the detritus food chain. Fallen → Earth → Black → Hawk T4 leaves worm bird (Detritus) (Detritivores) (Small (Top carnivores) carnivores) T3 T2 (i) Detritus food chain (DFC) always starts with (a) dead organic matter (b) living organic matter (c) gases matter (d) solid matter T1 (ii) DFC is the major fraction of energy flow in (a) pyramid of number in a grassland (a) aquatic (b) ariel ecosystem (c) terrestrial (d) none of these (iii) DFC ______ be connected with grazing food (b) pyramid of number in a pond ecosystem chain (GFC) at some level. (c) pyramid of number in a forest ecosystem (d) pyramid of biomass in a pond ecosystem (a) never (b) cannot (ii) Spindle shaped pyramid is a character of (c) may (d) always (iv) Which are essential part of the Detritus food ...................... . Chain (DFC)? (a) Pond ecosystem (a) decomposers (b) virus (b) Grassland ecosystem (c) producers (d) none of these (c) Parasite ecosystem (v) Which are the examples of decomposers (d) Forest ecosystem (a) bacteria only (b) virusandbacteria (iii) An inverted pyramid of biomass can be found (c) fungi and bacteria (d) fungi and virus in which ecosystem? 2. In a forest ecosystem, the pyramid of number is spindle in shape, it is because tthreeesba(Psero(dTu1c)eor)f (a) forest (b) marine the pyramid occupies large sized (c) Grassland (d) Tundra which eaartienglebsisredrs,ienlenpuhmanbtearn, dHdeerebri)voocrceuspy(Tin2g) (iv) Pyramid of energy is always (Fruit (a) upside down (b) upright second trophic level, are more in number than (c) horizontal (d) none of these (v) Observe the figures and select the correct type of pyramid of numbers. A BC A B C (a) Grassland ecosystem Forest ecosystem Parasite ecosystem (b) Grassland ecosystem Pond ecosystem Forest ecosystem (c) Forest ecosystem Grassland ecosystem Parasite ecosystem (d) Pond ecosystem Forest ecosystem Grassland ecosystem A ns. 1. (i) (a) (ii) (c) (iii) (c) (iv) (a) (v) (c) (v) (a) 2. (i) (c) (ii) (d) (iii) (b) (iv) (b) qqq Ecosystem  295

13 Biodiversity and its Conservation Topics Covered 1 3.1 Biodiversity 1 3.2 Biodiversity Conservation C hapter map BIODIVERSITY AND ITS CONSERVATION Biodiversity Conservation • Pattern of Biodiversity • Narrowly utilitarian (i) Latitudinal gradients • Broadly utilitarian (ii) Species-Area relationships • Way to conserve biodiversity • Loss of Biodiversity (i) In situ (on site) Causes: The Evil Quartet (a) endemism (b) sacred groves (i) Habitat loss and fragmentation (ii) Ex-situ (off site) (ii) Over-exploitation (a) Zoological parks (iii) Alien species invasions (b) Botanical gardens (iv) Co-extinctions (c) Wildlife safari Biodiversity means vast array of all the living organisms present on the earth. The term biodiversity was used by a socio-biologist Edward Wilson in his publications. Topic 1. Biodiversity Levels of biodiversity • Genetic diversity: It is the diversity of genes in a population of a species. For example, genetic variation shown by a medicinal plant Rouwolfia vomitaria growing in Himalayas may vary in yield and potency of active chemical reserpine. Similarly, in India, rice has more than 50,000 varieties and mango has more than 1000 varieties. • Species diversity: It is the diversity at species level. Example: Western Ghats are more rich in amphibian species than Eastern Ghats. • Ecological diversity: Different ecosystems are present in a country or a state refers to ecological diversity. Example: In India, various ecosystems like rain forests, coral reefs, deserts, wetlands, alpine meadows and estuaries are present. But a country like Norway will be less ecologically diverse than India. This vast biodiversity is a result of evolutionary changes happening since the formation of earth. How many species are there on Earth and how many in India? • According to IUCN (2004) more than 1.5 million species of plants and animals have been discovered and described so far and many more are waiting to be discovered. • Robert May estimated the total number of species present on earth to be 7 million. 296

Following figure represents the global biodiversity: Invertebrates Vertebrates Plants Other animal groups Mammals Crustaceans Mosses Ferns and allies Molluscs Birds Insects Fungi Angiosperms Reptiles Fishes Amphibians Algae Lichens • At present, more than 70% of all living organisms Seasonal variations in tropics is not present. TheSpecies richness are animals. weather remains constant and predictable. This promotes niche specialization leading to more • Plants make up for only 22%. diversity. • Insects among animals make up for more than 70%. Solar input is more in tropics, therefore productivity is more and can indirectly lead to • Although India has only 2.4 percent of world’s land greater bio-diversity. but the species diversity is 8.1% making India one of the 12 mega diverse countries. Species–Area Relationships • Number of species varies with respect to an area, • Around 45,000 species of plants and 90,000 species of animals have been recorded from India. with the increase in area, the species richness also increases but up to a limit. Beyond which increase Patterns of Biodiversity in area does not contribute to increase in species richness. Latitudinal gradients • This is represented as S = CAZ • On a log scale, the relationship is given as: • Distribution of plants and animals on earth is log S = log C + Z log A uneven. Where, S is species richness • The diversity follows a unique pattern called A is an area latitudinal gradient. Z represent slope of line or regression coefficient C = Y intercept • Species diversity decreases as we move away from equator towards poles. z S = CA • Tropics have more species than temperate and polar areas. Countries such as Colombia near equator log S = log C + Z log A have nearly 1400 species of birds and New York has 105 species and Greenland has only 56 species log-log scale of birds. • India, with most of its land falling in tropical region, is home to about 1200 species of birds. • A tropical region like Ecuador has 10 times more species of vascular plants than temperate regions. • Greatest biodiversity on earth is present in Amazon Area rain forest in South America. More than 40000 species of plants, 3000 species of fish, 1300 species • The value of Z line lies in the range of 0.1 to 0.2 of birds, 427 species of mammals, 427 species of • In larger continents, the Z-value ranges from 0.6 to amphibians, 378 species of reptiles and more the 1,25,000 invertebrates are present in this forest. 1.2, this gives much steeper slope. About two million insects are yet to be discovered and named. • In tropical forests, for fruit eating birds and mammals, the Z value is 1.15. • A hypothesis was proposed which justifies the presence of diverse tropics The Importance of Species Diversity to the Ecosystem Speciation is function of time. Temperate regions • A stable community should not show too much faced frequent glaciations in the past but tropical regions remained undisturbed for millions of years. variation in productivity from year to year. More time in tropics lead to greater diversity. • It should be resistant or resilient to natural or manmade disturbances. Biodiversity and its Conservation  297

• It must be resistant to alien species invasion. • Change in plant productivity, water use, pest and David Tilman in his experiments on some outdoor disease cycle. plots found that the plots with more species showed less year- to-year variation in total biomass and with Causes of loss of biodiversity increase in biodiversity productivity increased. • There are four major causes that lead to loss of Rivet Popper Hypothesis biodiversity, also called evil quartet. • Paul Ehrlich compared an airplane with an Habitat loss and fragmentation: Destruction ecosystem and its rivets with the species of that in habitat causes animals and plants to go extinct. ecosystem. Example: tropical rain forests are being destroyed • If rivets or species are removed from an airplane or very fast. Originally it covered 14% of total land an ecosystem, the airplane will crash upon its flight. on earth but now only 6% is left. Amazon rain Similarly ecosystem will also ultimately collapse forests are also called as lungs of the planet and become unstable. It is also important that the as these forests produce large amount of oxygen removed rivet is from which part of the airplane. If supporting all living organisms. This forest is rivet is removed from wings, the flight will be under losing its coverage area due to conversion into threat of crash. Similarly if key species is removed, cultivating land and grasslands. This breaks the ecosystem will no longer be stable. habitat into small fragments which in turn leads to population declines. Loss of Biodiversity • Human activities cause loss to biodiversity at very Over exploitation: Need of humans has now turned into greed and resources are over used faster rate. and over exploited. This has caused extinction of • According to IUCN Red list (2004), 338 vertebrates, many animals like stellar’s sea cow and passenger pigeon. Many commercially important marine 359 invertebrates and 87 plants (total 784 species) fishes have also become endangered. became extinct in last 500 years. • Dodo from Mauritius, Quagga from Africa, Thylacine Alien species invasions: When alien species from Australia, Steller’s Sea Cow from Russia and unintentionally or deliberately are introduced in a three sub species of tiger namely Javan, Bali and country for any purpose, they may become invasive Caspian got extinct in recent years. and becomes threat to indigenous species for their • 27 species became extinct in last 20 years. extinction. • Amphibians are more vulnerable to extinction. • 15,500 species are facing threat of extinction Nile perch when introduced into lake Victoria which includes 32% of amphibian species, 12% of in east Africa caused extinction of indigenous bird species, 23% of mammal species, and 31% of Cichlid fish. Similarly, Parthenium (carrot gymnosperms. grass), Lantana and Eicchornia (water hyacinth) Loss of biodiversity in a region may lead to became invasive to India. In Indian rivers, • Decline in plant production indigenous catfish species are facing threat due to • Lower resistance to environmental perturbations introduction of African catfish Clarias gariepinus. (deviation from the normal state) like droughts or floods. Co-extinctions: Two organisms with obligatory relationships go extinct together if any one of them gets extinct. A parasite meets the same fate if its host becomes extinct. Topic 2. Biodiversity Conservation lubricants, dyes, resins, perfumes; and products of medicinal importance. Why should we Conserve Biodiversity? Broadly utilitarian: We should conserve • Biodiversity should be conserved for following biodiversity because of its indirect values as it reasons: provides ecosystem services like oxygen, water, pollination, aesthetic pleasure etc. Narrowly utilitarian: We should conserve biodiversity as we get direct economic benefits from Ethical reasons: We should conserve our biodiversity such as food in the form of cereals, biodiversity as it is our moral duty to care for pulses and fruits; firewood; fiber; construction nature and to pass the legacy in good order to our material; industrial products like tannins, future generations. 298 Biology–12

How do we conserve Biodiversity? book. The concept of Red list was mooted in 1963. The Following strategies have been adopted for conserving purpose of preparation of Red List are: biodiversity: In situ conservation: • To create awareness on the degree of threat to biodiversity • In this approach, the species or organisms are protected by conserving them in their natural • Identification and documentation of species at high habitat such as we save entire forest to save tiger. risk of extinction Some of the biodiversity hotspots, the areas with high degree of species richness and endemism, are • Provide global index on declining biodiversity identified and protected. • Preparing conservation priorities and help in • Methods for IN SITU conservation are: conservation of action National parks • Information on international agreements on Sanctuaries conservation of biological diversity Red list has eight categories of species. Biodiversity hot spots (i) Extinct (ii) Extinct in wild (iii) Critically Endangered Biosphere reserves (iv) Endangered (v) Vulnerable (vi) Lower risk (vii) Data deficiency (viii) Not evaluated Sacred groves • Biosphere reserves: Large areas meant to Wetlands conserve a species for long time. Hot spots • National parks: An area with distinct boundaries in which wildlife along with its environment is • These are areas of high level of species richness, conserved. Many national parks can exist within a high endemism and high density of biodiversity (i.e., biosphere reserve. No poaching, forestry, cultivation megadiversity), but at the same time these are also and other developmental activities are allowed. The the most threatened areas. first national park in India, Jim Corbett National Park, Uttarakhand was established in 1936. Total • Econologically four factors determine hot spots: 103 National parks exist at present in India of which Kaziranga National Park and Manas National Species diversity and species density. Park in Assam, Nanda Devi National Park in Uttarakhand, Sunderbans National Park in West Degree of endemism (i.e., species confined to that Bengal, and Keoladeo National Park in Rajasthan region are not found anywhere else). have been declared as UNESCO world heritage sites. Degree of threat due to degradation, habitat loss and fragmentation. • Wildlife Sanctuary: An area reserved for conserving animal species. Some activities such Degree of exploitation. as collecting timber and minor forest products are allowed. Boundaries are not well defined. 515 • Three out of thirty-four hot spots (identified globally) wildlife sanctuaries are there in India out of which are in India—in Western Ghats, Himalays and Indo- 48 are tiger reserves. National Chambal wildlife Burma Regions. sanctuary, also called as tri state sanctuary, is the only sanctuary which is governed by three states of • Hot spots account for less than 2% of total area but India namely Madhya Pradesh, Uttar Pradesh and can reduce biodiversity loss (extinction) by 30%, if Rajasthan with headquarters at Morena, MP. It is conserved properly. known for conservation of small crocodile Gavialis gangeticus or gharial. Red-crowned roof turtle and Red Data Book Red Data book or Red list is a catalogue of taxa facing risk of extinction. IUCN – International Union of Conservation of Nature and Natural Resources, which is renamed as WCU – World Conservation Union (Morges Switzerland) maintains the Red Data Biodiversity and its Conservation  299