class 12 notes

Class 12 Biology Notes Chapter 9 (Strategies for Enhancement in Food Production) – Examplar Problems Book

Philoid

Philoid

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Examplar Problems
Alright class, let's get straight into Chapter 9: Strategies for Enhancement in Food Production. This is a crucial chapter, not just for your board exams but also for various competitive government exams where biology or general science is a component. We need to understand how we've managed to increase food production to meet the demands of a growing population and the scientific principles behind these strategies.

Chapter 9: Strategies for Enhancement in Food Production - Detailed Notes

1. Animal Husbandry

  • Definition: The agricultural practice of breeding and raising livestock (buffaloes, cows, pigs, horses, cattle, sheep, camels, goats, etc.) for human benefit (milk, eggs, meat, wool, silk, honey, etc.). It also includes poultry farming and fisheries.

  • Scope: Estimated 70% of the world's livestock population is in India and China, but their contribution to world farm produce is only 25%, indicating low productivity needing improvement through strategic management and breeding.

    • A. Dairy Farm Management:

      • Focus: Management of animals for milk and its products.
      • Key Aspects:
        • Breed Selection: Choosing breeds with high yield potential and resistance to diseases, suited to the local climate.
        • Housing: Well-ventilated, clean shelters protecting from elements.
        • Feeding: Balanced ration (quality and quantity of fodder + concentrates). Clean water supply.
        • Hygiene: Critical for both cattle and handlers to prevent diseases. Regular cleaning of sheds.
        • Health Care: Regular veterinary checks, vaccinations, disease monitoring, and prompt treatment. Record keeping is essential.

    • B. Poultry Farm Management:

      • Focus: Management of domesticated fowl (chickens, ducks, turkey, geese) for eggs and meat.
      • Key Aspects:
        • Breed Selection: Suitable breeds (e.g., Leghorn for eggs - layers; Broilers for meat).
        • Housing: Safe, disease-free, suitable conditions. Proper temperature.
        • Feed and Water: Balanced feed formulation, clean water.
        • Hygiene and Health Care: Strict sanitation, disinfection, vaccination programs (e.g., against bird flu).

    • C. Animal Breeding:

      • Aim: Increase yield and improve desirable qualities (growth rate, product quality, disease resistance, etc.).
      • Breed: A group of animals related by descent, similar in most characters (size, appearance, features).
      • Types of Breeding:
        • Inbreeding: Mating of more closely related individuals within the same breed for 4-6 generations.
          • Strategy: Select superior males and females of the same breed, mate them. Evaluate progeny, identify superior ones for further mating.
          • Advantages: Increases homozygosity, helps accumulate superior genes, eliminates undesirable genes. Develops pure lines (e.g., in cattle).
          • Disadvantages: Usually reduces fertility and productivity (Inbreeding Depression). Harmful recessive alleles may be exposed.
          • Solution for Inbreeding Depression: A single outcross (see below).
        • Outbreeding: Breeding of unrelated animals.
          • Out-crossing: Mating animals within the same breed but having no common ancestors for 4-6 generations. Best method to overcome inbreeding depression. Offspring are called out-crosses.
          • Cross-breeding: Superior males of one breed are mated with superior females of another breed. Combines desirable qualities of two different breeds. Progeny may be used for commercial production or further breeding. Example: Hisardale sheep (developed in Punjab by crossing Bikaneri ewes and Marino rams).
          • Interspecific Hybridisation: Mating between male and female animals of two different related species. Offspring combine desirable features of both parents but are often sterile. Example: Mule (cross between male donkey and female horse).

    • D. Controlled Breeding Experiments:

      • Artificial Insemination (AI): Semen collected from a selected superior male is introduced into the reproductive tract of the selected female.
        • Advantages: Overcomes problems of normal mating, semen can be transported (frozen - cryopreservation at -196°C in liquid nitrogen) and used later, semen from one bull can inseminate many cows.
      • Multiple Ovulation Embryo Transfer Technology (MOET): Used for herd improvement (cattle, sheep, rabbits, etc.).
        • Procedure:
          1. Cow administered hormones (with FSH-like activity) to induce follicular maturation and superovulation (produces 6-8 eggs instead of one).
          2. Cow is either mated with an elite bull or artificially inseminated.
          3. Fertilised eggs at 8-32 cell stage are recovered non-surgically.
          4. Eggs are transferred to surrogate mothers.
        • Advantages: Produces high milk-yielding females and high-quality meat-yielding bulls in a short time. Genetic mother available for another round of superovulation.

2. Apiculture (Bee-keeping)

  • Definition: Maintenance of hives of honeybees for the production of honey and beeswax.
  • Importance:
    • Honey: High nutritive value, used in indigenous medicine.
    • Beeswax: Used in cosmetics, polishes, candles.
    • Pollination: Bees are crucial pollinators for many crop species (sunflower, brassica, apple, pear). Keeping hives in crop fields increases pollination efficiency and improves crop yield.
  • Common Species: Apis indica (Indian bee). Apis mellifera (Italian bee) is often preferred due to high honey collection capacity, stinging less, and staying in a beehive longer.
  • Key Points for Success:
    • Knowledge of bee nature and habits.
    • Selection of suitable location with sufficient bee pastures (wild shrubs, fruit orchards, cultivated crops).
    • Catching and hiving of swarms (groups of bees).
    • Management of beehives during different seasons.
    • Handling and collection of honey and beeswax.

3. Fisheries

  • Definition: Industry devoted to catching, processing, or selling fish, shellfish (prawns, crabs, lobsters, oysters), or other aquatic animals.
  • Importance: Provides income and employment, rich source of animal protein.
  • Aquaculture: Production of useful aquatic plants and animals (fish, prawns, crabs, lobsters, molluscs etc.) by proper utilization of available waters.
  • Pisciculture: Specifically, the farming/rearing of fish.
  • Types:
    • Freshwater Fish: Catla, Rohu, Common Carp.
    • Marine Fish: Hilsa, Sardines, Mackerel, Pomfrets.
  • Blue Revolution: Focused efforts to increase fish production through aquaculture and pisciculture.

4. Plant Breeding

  • Definition: Purposeful manipulation of plant species to create desired plant types better suited for cultivation, giving better yields and disease resistance.

  • Classical Plant Breeding: Involves crossing or hybridisation of pure lines, followed by artificial selection to produce plants with desirable traits (higher yield, nutrition, resistance).

  • Main Steps in Breeding a New Genetic Variety:

    1. Collection of Variability: Collecting and preserving all different wild varieties, species, and relatives of the cultivated species (germplasm collection). This is the root of any breeding program.
    2. Evaluation and Selection of Parents: Evaluating the germplasm to identify plants with desirable combinations of characters. Selected plants are multiplied and used in hybridisation. Pure lines are created if desired.
    3. Cross Hybridisation among Selected Parents: Creating desired combinations by cross-pollinating two selected parents (e.g., one high protein quality, one disease resistant). Time-consuming and tedious process (emasculation, bagging, pollination). Results in hybrid progeny with combined traits.
    4. Selection and Testing of Superior Recombinants: Selecting offspring from the hybridisation that show the desired character combination. Requires careful scientific evaluation. Self-pollination for several generations is needed to achieve homozygosity (uniformity).
    5. Testing, Release, and Commercialisation of New Cultivars: Evaluating selected lines for yield, quality, disease resistance etc., in research fields under ideal conditions, then testing in farmers' fields across different agroclimatic zones for at least three growing seasons. If successful, it's certified and released as a new cultivar.

  • Green Revolution (Mid-1960s): Dramatic increase in food production (especially wheat and rice).

    • Key Factor: Development of semi-dwarf varieties of wheat and rice.
    • Wheat: Norman E. Borlaug (International Centre for Wheat and Maize Improvement, Mexico) developed semi-dwarf wheat. In 1963, varieties like Sonalika and Kalyan Sona (high yielding, disease resistant) were introduced in India.
    • Rice: Semi-dwarf rice varieties derived from IR-8 (developed at IRRI, Philippines) and Taichung Native-1 (from Taiwan). Later, better-yielding semi-dwarf varieties Jaya and Ratna were developed in India.
    • Sugarcane: Saccharum barberi (North India, poor sugar content/yield) successfully crossed with Saccharum officinarum (tropical South India, thicker stem, high sugar). Hybrid varieties combined high yield, thick stems, high sugar, and ability to grow in North India.
    • Millets: Hybrid maize, jowar, and bajra successfully developed in India (high yielding, water stress resistant).

  • A. Plant Breeding for Disease Resistance:

    • Impact: Diseases (caused by fungi, bacteria, viruses) reduce crop yield significantly (20-30% loss, sometimes total loss).
    • Goal: Develop resistant cultivars to reduce dependence on fungicides/bactericides.
    • Mechanisms of Resistance: Genetic basis.
    • Methods:
      • Conventional Breeding: Screening germplasm for resistance sources, hybridisation of selected parents, selection, and evaluation. Time-consuming. Examples:
        • Wheat: Himgiri (Leaf and stripe rust, hill bunt)
        • Brassica: Pusa Swarnim (Karan rai) (White rust)
        • Cauliflower: Pusa Shubhra, Pusa Snowball K-1 (Black rot, Curl blight black rot)
        • Cowpea: Pusa Komal (Bacterial blight)
        • Chilli: Pusa Sadabahar (Chilli mosaic virus, Tobacco mosaic virus, Leaf curl)
      • Mutation Breeding: Inducing mutations artificially using chemicals (e.g., EMS) or radiations (e.g., gamma rays), then screening the plant population for desirable mutations (like disease resistance). Example: Mung bean resistance to yellow mosaic virus and powdery mildew induced by mutations.
      • Selection among Somaclonal Variants: Variations found in plants regenerated from tissue culture.
      • Genetic Engineering: Transferring specific resistance genes (e.g., from wild relatives). Example: Resistance to yellow mosaic virus in bhindi (Abelmoschus esculentus) transferred from a wild species, resulting in a new variety called Parbhani kranti.

  • B. Plant Breeding for Insect Pest Resistance:

    • Impact: Insect infestation is a major cause of crop loss.
    • Resistance Factors:
      • Morphological: Hairy leaves (resistance to jassids in cotton, cereal leaf beetle in wheat), solid stems (resistance to stem sawfly in wheat), smooth leaves & nectar-less cotton (resistance to bollworms).
      • Biochemical: High aspartic acid, low nitrogen and sugar content in maize (resistance to stem borers).
    • Methods: Primarily conventional breeding (screening germplasm, hybridisation, selection). Examples:
      • Brassica (rapeseed mustard): Pusa Gaurav (Aphids)
      • Flat bean: Pusa Sem 2, Pusa Sem 3 (Jassids, aphids, fruit borer)
      • Okra (Bhindi): Pusa Sawani, Pusa A-4 (Shoot and Fruit borer)

  • C. Plant Breeding for Improved Food Quality (Biofortification):

    • Problem: Hidden hunger – deficiencies of micronutrients (vitamins, minerals) and protein, affecting health.
    • Solution: Breeding crops with higher levels of vitamins, minerals, higher protein, and healthier fats.
    • Objectives: Improve protein content/quality, oil content/quality, vitamin content, micronutrient/mineral content.
    • Examples:
      • Maize hybrids (2000): Twice the amount of amino acids lysine and tryptophan compared to existing hybrids.
      • Wheat variety: Atlas 66 (high protein content), used as a donor for improving cultivated wheat.
      • Rice: Iron-fortified variety (over 5 times more iron).
      • Vegetable Crops (IARI, New Delhi):
        • Vitamin A enriched: Carrots, Spinach, Pumpkin.
        • Vitamin C enriched: Bitter gourd, Bathua, Mustard, Tomato.
        • Iron and Calcium enriched: Spinach, Bathua.
        • Protein enriched: Beans (Broad, Lablab, French, Garden peas).

5. Single Cell Protein (SCP)

  • Concept: Using microbial biomass (bacteria, fungi like yeast, filamentous fungi, algae) as an alternative protein source for human food or animal feed.
  • Rationale: Addresses protein deficiency, reduces pressure on conventional agriculture which cannot meet the demand.
  • Microorganisms Used:
    • Spirulina (Blue-green algae): Grown easily on waste materials (straw, molasses, animal manure, sewage). Rich in protein, minerals, fats, carbohydrates, vitamins.
    • Methylophilus methylotrophus (Bacterium): High growth rate, can produce large quantities of protein (e.g., 250g microbe -> 25 tonnes protein).
    • Yeast (e.g., Candida utilis).
  • Advantages: High protein yield, rapid production, can utilize industrial/agricultural wastes (reducing pollution), less land required compared to conventional farming.

6. Tissue Culture

  • Concept: Growing whole plants from explants (any plant part) in vitro (in test tubes/culture vessels) under sterile conditions in a special nutrient medium. Based on totipotency (capacity of a cell/explant to generate a whole plant).
  • Requirements: Sterile conditions, specific nutrient medium (carbon source like sucrose, inorganic salts, vitamins, amino acids, growth regulators like auxins, cytokinins).
  • Applications:
    • Micropropagation: Producing thousands of plants through tissue culture in a short duration. Each plant is genetically identical to the original plant (a somaclone). Important for commercial propagation of tomato, banana, apple, orchids.
    • Recovery of Healthy Plants from Diseased Plants: The meristem (apical and axillary) is often free of viruses. By removing the meristem and growing it in vitro, virus-free plants can be obtained (e.g., banana, sugarcane, potato).
    • Somatic Hybridisation:
      • Protoplast: Plant cell without the cell wall (digested using enzymes cellulase and pectinase).
      • Process: Protoplasts isolated from two different varieties/species are fused to get hybrid protoplasts. These are cultured to form a new plant (somatic hybrid).
      • Example: Pomato - Protoplast fusion of potato and tomato. Aimed to combine characteristics, but the resulting plant did not have desired commercial utility. Still a valuable technique for combining traits that cannot be achieved through conventional sexual hybridisation.

Multiple Choice Questions (MCQs)

  1. Hisardale, a new breed of sheep developed in Punjab, was achieved by which breeding technique?
    a) Inbreeding
    b) Out-crossing
    c) Cross-breeding
    d) Interspecific Hybridisation

  2. Which of the following is the primary reason for using Multiple Ovulation Embryo Transfer (MOET) technology in cattle?
    a) To overcome inbreeding depression
    b) To produce large quantities of milk directly from the genetic mother
    c) To rapidly increase herd size with desirable traits from elite animals
    d) To create sterile offspring like mules

  3. 'Pusa Komal' is a disease-resistant variety of which crop, developed through conventional breeding?
    a) Wheat (resistant to rust)
    b) Cowpea (resistant to bacterial blight)
    c) Brassica (resistant to white rust)
    d) Chilli (resistant to mosaic virus)

  4. The technique of producing thousands of plants through tissue culture is called:
    a) Somatic hybridisation
    b) Micropropagation
    c) Mutation breeding
    d) Biofortification

  5. Which microorganism is commonly used for Single Cell Protein (SCP) production and can be grown easily on materials like molasses and sewage?
    a) Methylophilus methylotrophus
    b) Spirulina
    c) Saccharomyces cerevisiae
    d) Penicillium notatum

  6. Biofortification aims to improve crops primarily for:
    a) Increased yield
    b) Enhanced resistance to pests
    c) Higher nutritional value (vitamins, minerals, protein)
    d) Better adaptation to water stress

  7. The success of the Green Revolution in India, particularly for wheat, relied heavily on the introduction of:
    a) Hybrid varieties with high water requirements
    b) Varieties resistant only to fungal diseases
    c) Semi-dwarf, high-yielding, and disease-resistant varieties
    d) Genetically modified varieties with Bt toxin

  8. In plant breeding, the entire collection of plants/seeds having all the diverse alleles for all genes in a given crop is termed:
    a) Gene pool
    b) Genome
    c) Germplasm collection
    d) Cultivar library

  9. To obtain a virus-free plant from a virus-infected plant (like sugarcane or potato), which part is generally used for micropropagation?
    a) Leaf tissue
    b) Root tip
    c) Vascular tissue
    d) Apical or axillary meristem

  10. The fusion of naked protoplasts from two different plant varieties or species is a key step in:
    a) Artificial insemination
    b) Mutation breeding
    c) Somatic hybridisation
    d) Out-crossing

Answer Key for MCQs:

  1. c) Cross-breeding
  2. c) To rapidly increase herd size with desirable traits from elite animals
  3. b) Cowpea (resistant to bacterial blight)
  4. b) Micropropagation
  5. b) Spirulina
  6. c) Higher nutritional value (vitamins, minerals, protein)
  7. c) Semi-dwarf, high-yielding, and disease-resistant varieties
  8. c) Germplasm collection
  9. d) Apical or axillary meristem
  10. c) Somatic hybridisation

Make sure you understand these concepts thoroughly. Focus on the examples given for different breeding techniques and crop varieties, as they are frequently asked in exams. Good luck with your preparation!

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