A Textbook ofCBSE

Sarita Aggarwal M.Sc., B.Ed.

Former PGTModern School, Vasant Vihar

New Delhi

Former Principal Amity International School

Mayur Vihar, Phase-IDelhi

Strictly According to the New Syllabus Prescribed by the Central Board of Secondary Education

For Class Xii

With

Value Based

Questions

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© 2013, Sarita Aggarwal

All rights reserved. No part of this publication may be reproduced or copied in any material form (including photocopying or storing it in any medium in form of graphics, electronic or mechanical means and whether or not transient or incidental to some other use of this publication) without written permission of the publisher. Any breach of this will entail legal action and prosecution without further notice.Jurisdiction : All disputes with respect to this publication shall be subject to the jurisdiction of the Courts, Tribunals and Forums of New Delhi, India only.

First Published in 2013Reprints 2014, 2015Revised Edition 2016

ISBN : 978-93-525-3072-4 Code : 1003B 418

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Preface to the first editionThis comprehensive Textbook of CBSE Biology for Class XII has been written strictly in

accordance with the latest syllabus prescribed by the Central Board of Secondary Education.

Biology is a fascinating study of life. The book explains the essential concepts of biology to the students, linking them to examples in everyday life. Biologists, aided by new researches, have cracked the Human Genome Sequence; fortified crops (like Golden Rice), taken new stem cell initiatives and have been encountering new leaps in the field of tackling human diseases.

Thus, this textbook aims to teach biology to the students in such a manner so that they become informed citizens of the 21st century.

Some unique features of the book are :● Concise and accurate treatment of the subject matter● Very simple language within the comprehension of students.● Comparative tables to highlight the differences between important terms● Profusely illustrated with examples and well labelled diagrams● Subject matter (encompassed in the well etched sixteen chapters) is written in such a way

that makes the scientific concepts clear and understandable.● All the chapters contain new material as per the latest syllabus.● At the end of each chapter, Important Points and Key Terms have been given for quick

summary of the chapter.● According to the latest examination pattern (With Value Based Questions)● Variety of Review Questions for self assessment and recapitulation which include: Multiple choice questions, Fill in the blanks, Match the columns, True/False, NCERT

Textbook Questions (With solutions) and HOTS (Higher order Thinking Skills) Questions with solutions, Short Answer Type Questions and Long Answer Type Questions. It makes the students confident to tackle the competitive exams as well.

● Questions from latest Examination Paper (with Answers)We are thankful to the Management Team and the Editorial Department of S. Chand & Company

Pvt. Ltd. for all help and support in the publication of this book.Hope this book will meet the aspirations of the students for whom it has largely been written.

Suggestions for further improvement, along with constructive criticism, from teachers and students will be gratefully acknowledged.

AuThor

Disclaimer : While the author of this book has made every effort to avoid any mistake or omission and has used her skill, expertise and knowledge to the best of her capacity to provide accurate and updated information. The author and S. Chand do not give any representation or warranty with respect to the accuracy or completeness of the contents of this publication and are selling this publication on the condition and understanding that they shall not be made liable in any manner whatsoever. S. Chand and the author expressly disclaim all and any liability/responsibility to any person, whether a purchaser or reader of this publication or not, in respect of anything and everything forming part of the contents of this publication. S. Chand shall not be responsible for any errors, omissions or damages arising out of the use of the information contained in this publication.Further, the appearance of the personal name, location, place and incidence, if any; in the illustrations used herein is purely coincidental and work of imagination. Thus the same should in no manner be termed as defamatory to any individual.

ACKNOWLEDGEMENTSThe author wishes to express sincere thanks to her husband and daughters Shruti and Samridhi for their constant support and encouragement shown throughout the preparation of this book. She also wishes to extend gratitude to her parents without whose inspiration, this book would not have been possible.

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SyllabusCLASS XII(THeOry)

one Paper Time : 3 Hours No. of Periods Marks

Unit Title 1. Reproduction 30 14 2. Genetics and Evolution 40 18 3. Biology and Human Welfare 30 14 4. Biotechnology and its Applications 30 10 5. Ecology and Environment 30 14

Total 160 70

i. reproduction (30 Periods)

Reproduction in organisms: reproduction, a characteristic feature of all organisms for continuation of species; asexual reproduction modes of reproduction - asexual and sexual reproduction; asexual reproduction - binary fission, sporulation, budding, gemmule, fragmentation; vegetative propagation in plants.

Sexual reproduction in flowering plant: flower structure; development of male and female gametophytes; pollination - types, agencies and examples; outbreeding devices; pollen-pistil interaction; double fertilization; post fertilization events - development of endosperm and embryo, development of seed and formation of fruit; special modes-apomixis, parthenocarpy, polyembryony; Significance of seed dispersal and fruit formation.

Human Reproduction: male and female reproductive systems; microscopic anatomy of testis and ovary; gametogenesis - spermatogenesis and oogenesis; menstrual cycle; fertilisation, embryo development upto blastocyst formation, implantation; pregnancy and placenta formation (elementary idea); parturition (elementary idea); lactation (elementary idea).

Reproductive health: need for reproductive health and prevention of sexually transmitted diseases (STD); birth control – need and methods, contraception and medical termination of pregnancy (MTP); amniocentesis; infertility and assisted reproductive technologies – IVF, ZIFT, GIFT (elementary idea for general awareness).

ii. Genetics and Evolution (40 Periods)

Heredity and variation: Mendelian inheritance; deviations from Mendelism - incomplete dominance, co-dominance, multiple alleles and inheritance of blood groups, pleiotropy; elementary idea of polygenic inheritance; chromosome theory of inheritance; chromosomes and genes; Sex determination - in humans, birds and honey bee; linkage and crossing over; sex linked inheritance - haemophilia, colour blindness; Mendelian disorder

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in humans - thalassemia; chromosomal disorders in humans; Down’s syndrome, Turner’s and Klinefelter’s syndromes.

Molecular basis of inheritance: search for genetic material and DNA as genetic material; Structure of DNA and RNA; DNA packaging; DNA replication; Central dogma; transcription, genetic code, translation; gene expression and regulation - Lac Operon; Genome and human and rice genome project; DNA fingerprinting.

Evolution: origin of life; biological evolution and evidences for biological evolution (paleontology, comparative anatomy, embryology and molecular evidence); Darwin’s contribution, modern synthetic theory of evolution; mechanism of evolution - variation (mutation and recombination) and natural selection with examples, types of natural selection; Gene flow and genetic drift; Hardy - Weinberg’s principle; adaptive radiation; human evolution.

iii. Biology and Human Welfare (30 Periods)

Health and disease: pathogens; parasites causing human diseases (malaria, dengue, chicken guinea, filariasis, ascariasis, typhoid, pneumonia, common cold, amoebiasis, ring worm); Basic concepts of immunology - vaccines; cancer, HIV and AIDs; Adolescence, drug and alcohol abuse.

Improvement in food chicken production : Plant breeding, tissue culture, single cell protein, Biofortification, Apiculture and Animal husbandry.

Microbes in human welfare: In household food processing, industrial production, sewage treatment, energy generation and as biocontrol agents and biofertilizers. Antbiotics; production and judicious uses.

iV. Biotechnology and its applications (30 Periods)

Principles and process of biotechnology: genetic engineering (recombinant DNA technology). application of biotechnology in health and agriculture: human insulin and vaccine production, gene therapy; genetically modified organisms - Bt crops; transgenic animals; biosafety issues biopiracy and patents.

V. Ecology and Environment (30 Periods)

Organisms and environment: habitat and niche, population and ecological adaptations; population interactions - mutualism, competition, predation, parasitism; population attributes - growth, birth rate and death rate, age distribution.

Ecosystems: patterns, components; productivity and decomposition; energy flow; pyramids of number, biomass, energy; nutrient cycles (carbon and phosphorous); ecological succession; ecological services - carbon fixation, pollination, seed dispersal, oxygen release in brief).

Biodiversity and its conservation: concept of biodiversity; patterns of biodiversity; importance of biodiversity; loss of biodiversity; biodiversity conservation; hotspots, endangered organisms, extinction, Red Data Book, biosphere reserves, national parks and sanctuaries.

Environmental issues: Air larger pollution and its control; water pollution and its control; agrochemicals and their effects; solid waste management; radioactive waste management; greenhouse effect and global and climate change; ozone layer depletion; deforestation; any one case study as success story addressing environmental issues. Diseases; dengue and chickengunia.

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PrACTICALMaximum Marks : 30 (60 Periods)

a. list of Experiments

1. Study pollen germination on a slide.

2. Collect and study soil from at least two different sites and study them for texture, moisture content, pH and water holding capacity of soil. Correlate with the kinds of plants found in them.

3. Collect water from two different water bodies around you and study them for pH, clarity and presence of any living organisms.

4. Study the presence of suspended particulate matter in air at two widely different sites.

5. Study of plant population density by quadrate method.

6. Study of plant population frequency by quadrate method.

7. Prepare a temporary mount of onion root tip to study mitosis.

8. Study the effect of different temperatures and three different pH on the activity of salivary amylase on starch.

9. DNA banding in plant tissues.

study/observation of the following (spotting)

1. Flowers adapted to pollination by different agencies (wind, insect).

2. Pollen germination on stigma through a permanent slide.

3. Identification of stages of gamete development i.e. T.S. testis and T.S. ovary through permanent slides (from any mammal).

4. Meiosis in onion bud cell or grasshopper testis through permanent slides.

5. T.S. of blastula through permanent slides.

6. Mendelian inheritance using seeds of different colour/sizes of any plant.

7. Study prepared pedigree charts of any one of the genetic traits such as rolling of tongue, blood groups, ear lobes, widow’s peak and colour blindness.

8. Exercise on controlled pollination - emasculation, tagging and bagging.

9. Identification of common disease causing organisms like Ascaris, Entamoeba, Plasmodium, ringworm through permanent slides or specimens. Comment on symptoms of disease that they cause.

10. Two plants and two animals found in xeric conditions. Comment upon their morphological adaptations.

11. Plants and animals found in aquatic conditions. Comment upon their morphological adaptations.

Contents

Unit i – reProdUction

0 1. rEproDuCTion in orgAniSmS 3–40 1.1 Life Span 4 1.2 Reproduction 6 1.3 Asexual Reproduction 7 1.4 Vegetative Propagation 12 1.5 Sexual Reproduction 19 1.6 Events in Sexual Reproduction 23 1.7 Special Modes of Reproduction 30 1.8 Some Deviations in Sexually-Reproducing Animals 30 Important Points 31 Key Terms 32 Review Questions 33 NCERT Textbook Questions with Solutions 35 Higher Order Thinking Skills—Questions with Solutions 38

2. SExuAl rEproDuCTion in FlowEring plAnTS 41–82 2.1 Flower: A Fascinating Organ of Angiosperms 42 2.2 Pre-Fertilisation: Structures and Events 43 2.3 Pollination 54 2.4 Outbreeding Devices 60 2.5 Pollen-pistil Interaction 63 2.6 Pollen Germination 63 2.7 ArtificialHybridisation 65 2.8 Double Fertilization 66 2.9 Post-fertilization: Structures and Events 66 2.10 Apomixis and Polyembryony 72 Important Points 74 Key Terms 75 Review Questions 76 NCERT Textbook Questions with Solutions 79 Higher Order Thinking Skills—Questions with Solutions 81

3. HumAn rEproDuCTion 83–134 3.1 Human Reproductive System 84 3.2 Male Reproductive System 85 3.3 Female Reproductive System 88 3.4 Gametogenesis 91 3.5 Spermatogenesis 92 3.6 Oogenesis 95 3.7 The Ovarian or the Menstrual Cycle 99 3.8 Structure of Ova 102 3.9 Fertilisation 103 3.10 Changes from Egg to Embryo 106 3.11 Development of Human Embryo 114 3.12 Birth or Parturition 115

3.13 Lactation 116 Important Points 119 Key Terms 121 Review Questions 123 NCERT Textbook Questions with Solutions 130 Higher Order Thinking Skills—Questions with Solutions 132

4. rEproDuCTivE HEAlTH—proBlEmS AnD STrATEgiES 135–158 4.1 What is Reproductive Health? 136 4.2 Reproductive Health—Problems and Strategies 136 4.3 Population Explosion 138 4.4 Population Control 141 4.5 Medical Termination of Pregnancy (MTP) 146 4.6 Sexually Transmitted Diseases (STDs) 147 4.7 Infertility 148 4.8 Inequality of Sexes 149 Important Points 150 Key Terms 150 Review Questions 151 NCERT Textbook Questions with Solutions 153 Higher Order Thinking Skills—Questions with Solutions 156

Unit ii – Genetics and evolUtion

0 5. prinCiplES oF inHEriTAnCE AnD vAriATion 161–236 5.1 Mendel, the Founder of Genetics 162 5.2 Mendel’s Laws of Inheritance 164 5.3 Inheritance of One Gene 165 5.4 Inheritance of Two Genes 172 5.5 Other Patterns of Inheritance and Genetic Expression 175 5.6 Chromosomal Theory of Inheritance 184 5.7 Linkage and Crossing Over 188 5.8 Mapping on the Chromosomes — Genetic or Linkage Maps 194 5.9 Sex Determination 197 5.10 Causes of Genetic Variation 200 5.11 Pedigree Analysis 202 5.12 Human Genetic Disorders 203 5.13 Human Genetics 216 Important Points 220 Key Terms 222 Review Questions 224 NCERT Textbook Questions with Solutions 230 Higher Order Thinking Skills—Questions with Solutions 232

0 6. molECulAr BASiS oF inHEriTAnCE 237–316 6.1 Structure of Nucleic Acids (DNA and RNA) 238 6.2 Structure of DNA (Deoxyribonucleic Acid) 240 6.3 Structure of Chromosomes 245 6.4 The Search for Genetic Material 248 6.5 RNA World 254 6.6 Replication of DNA 254

6.7 Transcription (DNA to RNA Synthesis) 260 6.8 Genetic Code 268 6.9 Protein Synthesis 272 6.10 Regulation of Gene Expression 279 6.11 Genomics 284 6.12 Human Genome Project (HGP) 284 6.13 DNA Fingerprinting 289 6.14 Additional information on Gene Expression 295 6.15 Gene Expressions in Prokaryotes 298 Important Points 303 Key Terms 304 Review Questions 306 NCERT Textbook Questions with Solutions 312 Higher Order Thinking Skills—Questions with Solutions 313

0 7. EvoluTionAry Biology 317–387 7.1 Origin of Earth 318 7.2 Theories on the Origin of Life 319 7.3 Meaning of Evolution 327 7.4 Evidences for Evolution 327 7.5 Examples of Evolution by Natural Selection 335 7.6 ArtificialSelection 338 7.7 Adaptive Radiations 342 7.8 Biological Evolution 344 7.9 Mechanism of Evolution 348 7.10 Population Genetics and Evolution 351 7.11 Mutations 357 7.12 A Brief Account of Evolution 358 7.13 Concept of Species 362 7.14 Origin and Evolution of Man 367 Important Points 375 Key Terms 377 Review Questions 378 NCERT Textbook Questions with Solutions 384 Higher Order Thinking Skills—Questions with Solutions 385

Unit iii – bioloGy and hUman welfare

0 8. HumAn HEAlTH AnD DiSEASE 391–482 8.1 Health and Its Importance 392 8.2 Common Diseases in Humans 393 8.3 Communicable Diseases 397 8.4 Immunity 418 8.5 Innate (non-specific) Immunity 419 8.6 Acquired Immunity 422 8.7 Vaccination and Immunisation 434 8.8 Immune System Disorders 436 8.9 Lymphoid Organs 437 8.10 AIDS 440 8.11 Cancer 445 8.12 Adolescence and Drug/Alcohol Abuse 452

8.13 Alcohol Abuse 458 8.14 Smoking and Tobacco 464 Important Points 467 Key Terms 468 Review Questions 470 NCERT Textbook Questions with Solutions 477 Higher Order Thinking Skills—Questions with Solutions 481

09. STrATEgiES For EnHAnCEmEnT in FooD proDuCTion 483–532 9.1 Animal Husbandry 484 9.2 Plant Breeding 498 9.3 Main Steps in Breeding—A New Genetic Variety 499 9.4 Crop Improvement 506 9.5 Single Cell Protein (SCP) 515 9.6 Plant Tissue Culture 516 9.7 Plant Tissue Culture Techniques 522 Important Points 527 Key Terms 527 Review Questions 528 NCERT Textbook Questions with Solutions 529 Higher Order Thinking Skills—Questions with Solutions 531

10. miCroBES in HumAn wElFArE 533–557 10.1 Important Aspects of Microbes 534 10.2 Microbes in Household Products 535 10.3 Microbes in Industrial Products 537 10.4 Microbes in Sewage Treatment 541 10.5 Microbes in Production of Biogas 544 10.6 Microbes as Biocontrol Agents 545 10.7 Microbes as Biofertilisers 548 Important Points 551 Key Terms 551 Review Questions 552 NCERT Textbook Questions with Solutions 555 Higher Order Thinking Skills—Questions with Solutions 557

Unit iv – biotechnoloGy

11. BioTECHnology: prinCiplES AnD proCESSES 561–588

11.1 Principles of Biotechnology 562 11.2 Tools of Recombinant DNA (rDNA) Technology 565 11.3 Restriction Endonucleases 567 11.4 Separation and Isolation of DNA Fragments 569 11.5 Cloning Vectors or Vehicle DNA 571 11.6 Competent Host 573 11.7 Process of Recombinant DNA Technology 574 Important Points 579 Key Terms 580 Review Questions 580 NCERT Textbook Questions with Solutions 582 Higher Order Thinking Skills—Questions with Solutions 585

12. BioTECHnology AnD iTS AppliCATionS 589–624 12.1 Biotechnological Applications in Agriculture 590 12.2 Biotechnological Applications in Medicine 596 12.3 Molecular Diagnosis 600 12.4 Transgenic Animals 601 12.5 Cloning 603 12.6 Ethical Issues 608 12.7 Biopatent 609 12.8 Biopiracy 610 12.9 Biowar 613 Important Points 618 Key Terms 618 Review Questions 619 NCERT Textbook Questions with Solutions 621 Higher Order Thinking Skills—Questions with Solutions 623

Unit v – ecoloGy and environment

13. orgAniSmS AnD populATionS 627–725 13.1 DefinitionofEcology 629 13.2 Levels of Organisation 630 13.3 Organism and its Environment 633 13.4 Major Biomes 637 13.5 Major Abiotic Factors 645 13.6 Response to Abiotic Factors 664 13.7 Range of Tolerance 667 13.8 Adaptations 669 13.9 Populations 683 13.10 Life History Variation 690 13.11 Population Interactions 690 13.12 Biotic Community Organisation 702 13.13 Community Characteristics 703 13.14 Analysis of Plant Communities 706 Important Points 709 Key Terms 712 Review Questions 714 NCERT Textbook Questions with Solutions 720 Higher Order Thinking Skills—Questions with Solutions 723

14. ECoSySTEm 726–783 14.1 Ecosystem—Structure and Function 727 14.2 Productivity 732 14.3 Decomposition 736 14.4 Energy Flow 739 14.5 Ecological Pyramids 749 14.6 EcologicalEfficiencies 751 14.7 Ecological Succession 752 14.8 Nutrient Cycling 760 14.9 Biogeochemical Cycles 764 14.10 Ecosystem Services 769 Important Points 771 Key Terms 772

Review Questions 774 NCERT Textbook Questions with Solutions 779 Higher Order Thinking Skills—Questions with Solutions 781

15. BioDivErSiTy AnD ConSErvATion 784–829 15.1 Biodiversity 785 15.2 Levels of Biodiversity 785 15.3 Biogeographical Regions of India 790 15.4 Magnitude of Diversity 790 15.5 Patterns of Biodiversity 793 15.6 Importance of Species Diversity to the Ecosystem 797 15.7 Loss of Biodiversity 799 15.8 Extinction of Species 800 15.9 Causes of Biodiversity Losses 805 15.10 Biodiversity Conservation 808 15.11 Hotspots of Biodiversity 812 15.12 International Efforts for Conserving Biodiversity 819 15.13 Biodiversity Conservation in India 820 Important Points 821 Key Terms 822 Review Questions 823 NCERT Textbook Questions with Solutions 826 Higher Order Thinking Skills—Questions with Solutions 828

16. EnvironmEnTAl iSSuES 830–902 16.1 Pollution 831 16.2 Air Pollution 833 16.3 Control of Air Pollution 841 16.4 Controlling Vehicular Air Pollution: A Case Study of Delhi 844 16.5 Noise Pollution 846 16.6 Water Pollution and its Control 848 16.7 Solid Wastes 859 16.8 Agro-chemicals and their Effects 862 16.9 Soil Pollution 863 16.10 Radioactive Waste 866 16.11 Radioactive Pollution 867 16.12 Global Environmental Change 870 16.13 Effects of Abundance of Greenhouse Gases 875 16.14 Ozone Depletion in the Stratosphere 879 16.15 Degradation (of soil) by Improper Resource Utilisation and Maintenance 883 16.16 Deforestation 886 16.17 Case Study of People’s Participation in Conservation of Forests 889 Important Points 891 Key Terms 892 Review Questions 894 NCERT Textbook Questions with Solutions 898 Higher Order Thinking Skills—Questions with Solutions 900 vAluE BASED QuESTionS 903–911 QuESTion pApErS, 2013 (wiTH SoluTion) 912–922 QuESTion pApErS, 2014 (wiTH SoluTion) 923–952 QuESTion pApErS, 2015 953–956

UNIT I

REPRODUCTION

A Textbook Of CBSE Biology For ClassXII

Publisher : SChand Publications ISBN : 9789352530724 Author : Sarita Aggarwal

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