Class 12 Notes

Class 12 Biology Notes Chapter 17 (Answers to MCQs) – Examplar Problems Book

Philoid

Philoid

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Examplar Problems
Detailed Notes with MCQs of Chapter 17 from your NCERT Exemplar Biology book. Now, remember, this chapter itself doesn't introduce new biological concepts. Instead, it provides the answers to the Multiple Choice Questions (MCQs) presented in the previous chapters (Chapters 1 through 16).

For your government exam preparation, simply knowing the answers (like '1-c, 2-a, 3-d') isn't enough. You need to understand why a particular option is correct. Chapter 17 serves as a validation tool – after you attempt the MCQs from Chapters 1-16, you use Chapter 17 to check your understanding.

So, the "notes" for Chapter 17 are essentially a reinforcement of the key concepts tested in the MCQs of the entire syllabus covered in the Exemplar. Let's quickly recap the core ideas from each preceding chapter that the MCQs likely tested, which you would verify using Chapter 17.

Key Concepts Reinforced by Exemplar MCQs (Verified via Chapter 17 Answers):

  • Chapter 1: Reproduction in Organisms:

    • Distinction between asexual and sexual reproduction.
    • Modes of asexual reproduction (binary fission, budding, gemmules, fragmentation, vegetative propagation - runners, rhizomes, suckers, tubers, offsets, bulbs) with examples.
    • Phases of life cycle (Juvenile, Reproductive, Senescent).
    • Events in sexual reproduction: Pre-fertilisation (gametogenesis, gamete transfer), Fertilisation (syngamy - external/internal), Post-fertilisation (zygote formation, embryogenesis).
    • Concepts like clones, parthenogenesis, hermaphrodites, monoecious/dioecious conditions.

  • Chapter 2: Sexual Reproduction in Flowering Plants:

    • Structure of a flower, microsporangium (pollen sac), megasporangium (ovule).
    • Microsporogenesis (pollen grain formation) and Megasporogenesis (embryo sac formation - monosporic development).
    • Structure of pollen grain and embryo sac (7-celled, 8-nucleate).
    • Pollination: Types (autogamy, geitonogamy, xenogamy), agents (wind, water, insects, etc.), adaptations.
    • Pollen-pistil interaction, artificial hybridisation (emasculation, bagging).
    • Double fertilization and triple fusion: Significance, products (zygote, PEN leading to endosperm).
    • Post-fertilisation changes: Development of endosperm, embryo (dicot/monocot), seed (albuminous/non-albuminous), fruit (true/false, parthenocarpic).
    • Apomixis and Polyembryony.

  • Chapter 3: Human Reproduction:

    • Structure and functions of Male and Female reproductive systems.
    • Gametogenesis: Spermatogenesis and Oogenesis (process, hormonal control).
    • Structure of sperm and ovum.
    • Menstrual cycle: Phases, hormonal regulation (FSH, LH, estrogen, progesterone).
    • Fertilisation, cleavage, implantation.
    • Pregnancy: Placenta (structure, functions, hormones - hCG, hPL), embryonic development (germ layers and organogenesis).
    • Parturition (signals, hormonal control - oxytocin) and Lactation (colostrum, hormonal control - prolactin).

  • Chapter 4: Reproductive Health:

    • Meaning, problems, and strategies (RCH programmes).
    • Population explosion: Causes, consequences.
    • Contraceptive methods: Natural (periodic abstinence, withdrawal, lactational amenorrhea), Barrier (condoms, diaphragms, cervical caps, vaults), IUDs (non-medicated, copper-releasing, hormone-releasing), Oral pills, Injectables, Implants, Surgical (vasectomy, tubectomy).
    • Medical Termination of Pregnancy (MTP): Legal aspects, safety.
    • Sexually Transmitted Infections (STIs): Causative agents, prevention.
    • Infertility: Causes, Assisted Reproductive Technologies (ART) - IVF-ET, ZIFT, GIFT, ICSI, AI.

  • Chapter 5: Principles of Inheritance and Variation:

    • Mendel's experiments, Laws of Inheritance (Dominance, Segregation, Independent Assortment).
    • Deviations from Mendelism: Incomplete dominance, Co-dominance, Multiple alleles (ABO blood groups), Pleiotropy.
    • Chromosomal theory of inheritance (Sutton and Boveri).
    • Linkage and Recombination: Morgan's work on Drosophila.
    • Sex determination: Mechanisms (XX-XY, XX-XO, ZW-ZZ, Haplodiploidy).
    • Mutation: Point mutation, Frameshift mutation.
    • Pedigree analysis: Symbols, interpretation of inheritance patterns.
    • Genetic disorders: Mendelian (Haemophilia, Sickle-cell anaemia, Phenylketonuria, Thalassemia, Cystic fibrosis), Chromosomal (Aneuploidy - Down's syndrome, Klinefelter's syndrome, Turner's syndrome).

  • Chapter 6: Molecular Basis of Inheritance:

    • DNA as genetic material: Griffith's experiment, Avery-MacLeod-McCarty experiment, Hershey-Chase experiment.
    • Structure of DNA (Watson-Crick model), RNA.
    • DNA packaging (nucleosome model).
    • DNA replication: Semi-conservative mode (Meselson-Stahl experiment), enzymes involved.
    • Central Dogma.
    • Transcription: Process, transcription unit, RNA types (mRNA, tRNA, rRNA).
    • Genetic code: Features (triplet, universal, non-ambiguous, degenerate, non-overlapping, commaless).
    • Translation: Process (activation, initiation, elongation, termination), role of ribosomes and tRNA.
    • Regulation of gene expression: Operon concept (Lac operon).
    • Human Genome Project (HGP): Goals, methodology, findings.
    • DNA fingerprinting: Principle (VNTRs), technique, applications.

  • Chapter 7: Evolution:

    • Origin of life: Theories (Special creation, Spontaneous generation, Biogenesis, Chemical evolution - Oparin-Haldane hypothesis, Miller-Urey experiment).
    • Evidences for evolution: Paleontological, Comparative anatomy (Homologous & Analogous structures), Embryological (von Baer's law), Biogeographical, Biochemical.
    • Theories of evolution: Lamarckism, Darwinism (Natural selection, Branching descent).
    • Mechanism of evolution: Hardy-Weinberg principle, factors affecting equilibrium (gene migration/flow, genetic drift - founder effect, mutation, recombination, natural selection - types).
    • Adaptive radiation (Darwin's finches, Australian marsupials).
    • Brief account of evolution: Origin of vertebrates, timeline.
    • Human evolution: Stages, key features.

  • Chapter 8: Human Health and Diseases:

    • Common infectious diseases: Causative agents, symptoms, transmission, prevention/control (Typhoid, Pneumonia, Common cold, Malaria, Amoebiasis, Ascariasis, Filariasis, Ringworm).
    • Immunity: Innate (barriers), Acquired (active/passive, natural/artificial), Humoral (B-cells, antibodies), Cell-mediated (T-cells).
    • Vaccination and Immunisation.
    • Allergy, Autoimmunity.
    • Immune system: Lymphoid organs (primary/secondary), cells.
    • AIDS: Causative agent (HIV), transmission, mechanism, prevention.
    • Cancer: Types, causes (carcinogens), detection, treatment.
    • Drugs and Alcohol abuse: Effects, addiction, dependence, prevention, control.

  • Chapter 9: Strategies for Enhancement in Food Production:

    • Animal husbandry: Management of farms (dairy, poultry).
    • Animal breeding: Objectives, methods (inbreeding, outbreeding - out-crossing, cross-breeding, interspecific hybridisation), MOET.
    • Apiculture (Bee-keeping), Fisheries (Pisciculture, Aquaculture).
    • Plant breeding: Steps (collection of variability, evaluation & selection, cross hybridisation, testing & release), breeding for disease resistance, pest resistance, improved food quality (biofortification).
    • Single Cell Protein (SCP).
    • Tissue culture: Totipotency, micropropagation, somatic hybridisation, applications.

  • Chapter 10: Microbes in Human Welfare:

    • Household products: Curd (LAB), Dough, Toddy, Cheese.
    • Industrial products: Fermented beverages, Antibiotics (Penicillin discovery), Chemicals (acids, alcohol, enzymes - lipases, pectinases, proteases), Bioactive molecules (Cyclosporin A, Statins).
    • Sewage treatment: Primary treatment, Secondary treatment (aerobic microbes, activated sludge, BOD concept), Biogas production (methanogens).
    • Microbes as Biocontrol agents: Examples (Ladybird, Dragonflies, Bacillus thuringiensis, Trichoderma, Baculoviruses).
    • Microbes as Biofertilisers: Examples (Rhizobium, Azotobacter, Azospirillum, Mycorrhiza, Cyanobacteria).

  • Chapter 11: Biotechnology: Principles and Processes:

    • Principles: Genetic engineering (rDNA technology), Maintenance of sterile conditions.
    • Tools of rDNA technology: Restriction enzymes (types, nomenclature, action), Cloning vectors (features - ori, selectable marker, cloning sites; examples - plasmids, bacteriophages), Ligase, Competent host.
    • Processes of rDNA technology: Isolation of DNA, Fragmentation by restriction endonucleases, Isolation of desired DNA fragment (gel electrophoresis), Ligation into vector, Transformation of host cell, Culturing host cells, Extraction of desired product.
    • Polymerase Chain Reaction (PCR): Principle, steps, applications.
    • Bioreactors: Purpose, types (stirred-tank).
    • Downstream processing.

  • Chapter 12: Biotechnology and its Applications:

    • Agriculture: Bt crops (e.g., Bt cotton), Pest-resistant plants (RNA interference - nematode resistance in tobacco), production of nutritionally enhanced crops (e.g., Golden Rice - though not explicitly detailed in NCERT, the concept of biofortification via biotech applies).
    • Medicine: Genetically engineered insulin production, Gene therapy (example: ADA deficiency), Molecular diagnosis (PCR, ELISA), Transgenic animals (uses).
    • Ethical issues: Biopiracy, patents, GEAC (Genetic Engineering Approval Committee).

  • Chapter 13: Organisms and Populations:

    • Ecology levels: Organism, Population, Community, Ecosystem.
    • Organism and its environment: Major abiotic factors (temperature, water, light, soil), responses to abiotic factors (regulate, conform, migrate, suspend).
    • Adaptations: Morphological, physiological, behavioural examples.
    • Population attributes: Birth rate, death rate, sex ratio, age structure (age pyramids).
    • Population growth: Growth models (exponential - J-shaped curve, logistic - S-shaped curve, carrying capacity 'K').
    • Population interactions: Predation, Competition (Gause's principle, resource partitioning), Parasitism, Commensalism, Mutualism, Amensalism - with examples.

  • Chapter 14: Ecosystem:

    • Structure: Components (biotic, abiotic), stratification.
    • Function: Productivity (Primary - GPP, NPP; Secondary), Decomposition (steps: fragmentation, leaching, catabolism, humification, mineralisation; factors affecting), Energy flow (Unidirectional, 10% law, food chain - GFC/DFC, food web), Ecological pyramids (number, biomass, energy - upright/inverted).
    • Ecological succession: Definition, types (primary/secondary, hydrarch/xerarch), pioneer species, climax community.
    • Nutrient cycling: Biogeochemical cycles (Gaseous - Carbon cycle; Sedimentary - Phosphorus cycle).
    • Ecosystem services: Examples (pollination, nutrient cycling, aesthetic value).

  • Chapter 15: Biodiversity and Conservation:

    • Levels of biodiversity: Genetic, Species, Ecological.
    • Patterns of biodiversity: Latitudinal gradients, Species-area relationship (Alexander von Humboldt).
    • Importance of biodiversity: Narrowly utilitarian, Broadly utilitarian, Ethical arguments.
    • Loss of biodiversity: The 'Evil Quartet' (Habitat loss and fragmentation, Over-exploitation, Alien species invasions, Co-extinctions).
    • Biodiversity conservation: Why conserve? How to conserve?
      • In-situ conservation: Biodiversity hotspots, National Parks, Sanctuaries, Biosphere Reserves, Sacred Groves.
      • Ex-situ conservation: Zoological parks, Botanical gardens, Wildlife safari parks, Cryopreservation, Seed banks.
    • International efforts: Earth Summit (Rio, 1992), World Summit on Sustainable Development (Johannesburg, 2002).

  • Chapter 16: Environmental Issues:

    • Air pollution and control: Causes (particulates, gases), effects (respiratory problems, acid rain), control methods (electrostatic precipitator, scrubber, catalytic converter), controlling vehicular pollution (CNG, Euro norms). Noise pollution.
    • Water pollution and control: Sources (domestic sewage, industrial effluents), effects (BOD, eutrophication, biomagnification), prevention. Integrated wastewater treatment (including ecological sanitation - EcoSan toilets).
    • Solid wastes: Types, management (recycling, incineration, landfills), electronic wastes (e-wastes). Case study of plastic waste remedy (Ahmed Khan).
    • Agro-chemicals and their effects. Organic farming (Case study: Ramesh Chandra Dagar).
    • Radioactive wastes.
    • Greenhouse effect and Global warming: Causes, consequences, control.
    • Ozone depletion: Causes (CFCs), effects (UV-B radiation), Montreal Protocol.
    • Degradation by improper resource utilisation: Soil erosion, desertification, waterlogging, soil salinity.
    • Deforestation: Causes, consequences. Reforestation. People's participation (Chipko Movement, Joint Forest Management - JFM).

Remember, the Exemplar MCQs often test application, analysis, and connections between concepts. Use Chapter 17 not just to find the right answer, but to understand the reasoning and solidify your grasp on these fundamental topics.

Practice MCQs (Based on Exemplar Style):

  1. Which of the following represents a correct sequence in the development of a female gametophyte in angiosperms?
    (a) Megaspore Mother Cell → Meiosis → 4 Megaspores (linear tetrad) → 3 Degenerate → Functional Megaspore → Mitosis (3 times) → 8 Nuclei → 7-celled Embryo Sac
    (b) Megaspore Mother Cell → Mitosis → 4 Megaspores → 1 Degenerates → Functional Megaspore → Meiosis (3 times) → 8 Nuclei → 7-celled Embryo Sac
    (c) Microspore Mother Cell → Meiosis → 4 Microspores → Pollen Grain → Generative cell division → 2 Male gametes
    (d) Megaspore Mother Cell → Meiosis → 4 Megaspores (isobilateral tetrad) → All functional → 4 Embryo Sacs per ovule

  2. A man whose father was colour blind marries a woman who had a colour blind mother and a normal father. What percentage of male children of this couple will be colour blind? (Colour blindness is an X-linked recessive trait).
    (a) 25%
    (b) 0%
    (c) 50%
    (d) 75%

  3. Match the following columns regarding tools of rDNA technology:

    Column I Column II
    (A) Restriction Enzyme (i) Seals nicks in DNA backbone
    (B) DNA Ligase (ii) Selectable marker gene
    (C) Plasmid Vector (iii) Molecular scissors
    (D) Ampicillin Res. (iv) Used for gene cloning

    (a) A-(iii), B-(i), C-(iv), D-(ii)
    (b) A-(iii), B-(iv), C-(i), D-(ii)
    (c) A-(ii), B-(i), C-(iv), D-(iii)
    (d) A-(iv), B-(iii), C-(ii), D-(i)

  4. Which of the following population interactions is incorrectly matched with its effect on the interacting species (+ for beneficial, - for detrimental, 0 for neutral)?
    (a) Mutualism (+/+)
    (b) Competition (-/-)
    (c) Parasitism (+/-)
    (d) Commensalism (+/-)

  5. The primary treatment of sewage involves:
    (a) Biological oxidation by microbes
    (b) Removal of dissolved impurities by chemical precipitation
    (c) Physical removal of large and small particles through filtration and sedimentation
    (d) Anaerobic digestion of sludge by methanogens

  6. During the process of transcription in eukaryotes, the RNA polymerase III is responsible for transcribing:
    (a) mRNA precursors (hnRNA)
    (b) 18S, 5.8S, and 28S rRNA
    (c) tRNA, 5S rRNA, and snRNAs
    (d) Only mRNA

  7. Cryopreservation is a technique used in:
    (a) In-situ conservation only
    (b) Ex-situ conservation only
    (c) Both in-situ and ex-situ conservation
    (d) Neither in-situ nor ex-situ conservation, but in tissue culture

  8. The phenomenon where a single gene exhibits multiple phenotypic expressions is called:
    (a) Co-dominance
    (b) Incomplete dominance
    (c) Pleiotropy
    (d) Polygenic inheritance

  9. Which of the following is NOT a consequence of ozone layer depletion?
    (a) Increased incidence of skin cancer
    (b) Damage to cornea (snow-blindness)
    (c) Reduced primary productivity in phytoplankton
    (d) Increased concentration of greenhouse gases leading to global warming

  10. The technique of MOET (Multiple Ovulation Embryo Transfer) is primarily used for:
    (a) Producing disease-resistant plant varieties
    (b) Improving herd size and quality in cattle rapidly
    (c) Producing large quantities of single-cell protein
    (d) Developing pest-resistant Bt crops

Answers to MCQs:

  1. (a)
  2. (c)
  3. (a)
  4. (d) [Commensalism should be (+/0)]
  5. (c)
  6. (c)
  7. (b)
  8. (c)
  9. (d) [Ozone depletion and global warming are distinct issues, though both are environmental concerns]
  10. (b)

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