Class 12 Biology Notes Chapter 9 (Strategies for enhancement in food production) – Biology Book

Detailed Notes with MCQs of Chapter 9: 'Strategies for Enhancement in Food Production'. This chapter is crucial as it deals with the application of biological principles to increase food yield, addressing the ever-growing global population demands. For your government exam preparation, pay close attention to the specific techniques, examples, and terminology used.

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

1. Introduction
The increasing human population necessitates a significant enhancement in food production. Traditional methods alone are insufficient. Biological principles applied to animal husbandry and plant breeding play a vital role in achieving increased food production through various strategies.

2. Animal Husbandry
Animal husbandry is the agricultural practice of breeding and raising livestock (like buffaloes, cows, pigs, horses, cattle, sheep, camels, goats, etc.) for human benefit – primarily for food (milk, meat, eggs), fibre (wool), or labour. It also includes poultry farming and fisheries.

• Management of Farms and Farm Animals:

  • Dairy Farm Management: Deals with processes and systems that increase yield and improve the quality of milk and its products.
    • Key Aspects:
      • Breed Selection: Choosing high-yielding breeds with resistance to diseases is fundamental. Potential needs to be combined with optimal environmental conditions (housing, water) and feeding.
      • Feeding: Quality and quantity of fodder are crucial. Balanced rations including roughage and concentrates are necessary.
      • Housing: Well-ventilated, adequate space, clean shelters protect animals from weather conditions and facilitate clean milk production.
      • Water: Adequate clean water supply.
      • Hygiene: Strict cleanliness and hygiene (both of cattle and handlers) are paramount during milking, storage, and transport.
      • Health Care: Regular veterinary checks, vaccinations, and disease control are essential.
  • Poultry Farm Management: Raising domesticated fowl (chickens, ducks, turkeys, geese) for eggs and meat.
    • Key Aspects:
      • Breed Selection: Disease-free and suitable breeds (e.g., Leghorn for eggs, Plymouth Rock for meat).
      • Housing: Safe and suitable farm conditions.
      • Feed and Water: Proper feed and clean water.
      • Hygiene and Health Care: Maintaining hygiene and implementing disease control measures (e.g., preventing bird flu).

• Animal Breeding: Aims to increase the yield of animals and improve the desirable qualities of the produce.

  • Breed: A group of animals related by descent and similar in most characters like general appearance, features, size, configuration, etc.

  • Objectives: Increased production (milk, meat, eggs, wool), improved quality, disease resistance, faster growth rate, improved reproductive efficiency.

  • Types of Breeding:

    • Inbreeding: Mating of more closely related individuals within the same breed for 4-6 generations.
      • Strategy: Superior males and superior females of the same breed are identified and mated. Progeny evaluated, and superior ones are further mated.
      • Advantages: Increases homozygosity, helps accumulate superior genes, eliminates less desirable genes. Useful for developing pure lines (e.g., in cattle).
      • Disadvantage: Inbreeding Depression - Continued close inbreeding usually reduces fertility and even productivity. Overcome by a single out-cross (mating with unrelated superior animals of the same breed).
    • Outbreeding: Breeding of unrelated animals.
      • Out-crossing: Mating animals within the same breed but having no common ancestors on either side for 4-6 generations. Best breeding method for animals below average in productivity (milk production, growth rate). Helps overcome inbreeding depression.
      • Cross-breeding: Superior males of one breed are mated with superior females of another breed. Progeny (hybrids) may combine desirable qualities of both parents and often show hybrid vigour (heterosis). Used for developing new stable breeds (e.g., Hisardale sheep developed in Punjab by crossing Bikaneri ewes and Marino rams).
      • Interspecific Hybridisation: Mating between males and females of two different related species. Progeny combine desirable features of both parents but are often sterile. Example: Mule (cross between male donkey and female horse).

  • Controlled Breeding Experiments:

    • Artificial Insemination (AI): Semen collected from a superior male is injected into the reproductive tract of the selected female.
      • Advantages: Overcomes problems of normal mating, semen can be used immediately or frozen for later use, semen can be transported, allows mating between animals located far apart, semen from one bull can inseminate several cows.
    • Multiple Ovulation Embryo Transfer Technology (MOET): Program for herd improvement (cattle, sheep, rabbits, buffaloes, mares, etc.).
      • Procedure:
        1. A cow is administered hormones (like FSH) to induce follicular maturation and superovulation (produces 6-8 eggs instead of one).
        2. The cow is either mated with an elite bull or artificially inseminated.
        3. Fertilised eggs (zygotes) at the 8-32 cell stage are recovered non-surgically.
        4. These embryos are transferred to surrogate mothers.
        5. The genetic mother is available for another round of superovulation.
      • Advantages: Increases herd size of desired genetic makeup in a short time, produces high milk-yielding females and high-quality meat-yielding bulls quickly.

• Bee-keeping (Apiculture): Maintenance of hives of honeybees for the production of honey and beeswax.

  • Importance: Honey (high nutritive value, medicinal uses), Beeswax (used in cosmetics, polishes, candles), Pollination (bees are pollinators for many crop species like sunflower, Brassica, apple, pear).
  • Common Species: Apis indica (Indian bee).
  • Key Points for Successful Bee-keeping: Knowledge of bee nature and habits, selection of suitable location for hives, catching and hiving of swarms, management of hives during different seasons, handling and collection of honey and beeswax.

• Fisheries: Industry devoted to catching, processing, or selling fish, shellfish, or other aquatic animals (prawn, crab, lobster, edible oyster).

  • Importance: Provides income and employment, source of protein-rich food.
  • Types: Freshwater (Catla, Rohu, Common Carp) and Marine (Hilsa, Sardines, Mackerel, Pomfrets).
  • Aquaculture: Production of useful aquatic plants and animals.
  • Pisciculture: Specifically fish farming.
  • Blue Revolution: The large increase in fish production through aquaculture and pisciculture.

3. Plant Breeding
Purposeful manipulation of plant species to create desired plant types better suited for cultivation, giving better yields and being disease resistant. It is a key part of the Green Revolution.

• Objectives: Increased crop yield, improved quality (nutritional value, baking quality, protein content, oil content etc.), increased tolerance to environmental stresses (salinity, extreme temperatures, drought), resistance to pathogens (viruses, fungi, bacteria), resistance to insect pests.

• Main Steps in Breeding a New Genetic Variety:

  1. Collection of Variability (Germplasm Collection): Genetic variability is the root of any breeding program. Collection and preservation of all different wild varieties, species, and relatives of the cultivated species (entire collection = germplasm).
  2. Evaluation and Selection of Parents: Germplasm is evaluated to identify plants with desirable combinations of characters. Selected plants are multiplied and used in hybridization. Pure lines are created if desired.
  3. Cross Hybridisation among Selected Parents: Desired characters from two different parents are combined. E.g., high protein quality of one parent + disease resistance of another. This involves emasculation (if needed) and pollination to produce hybrid progeny. Tedious and time-consuming.
  4. Selection and Testing of Superior Recombinants: Selection among the progeny of the hybrids that have the desired character combination. Requires careful scientific evaluation. Progeny plants that are superior to both parents are self-pollinated for several generations till they reach homozygosity (uniformity).
  5. Testing, Release, and Commercialisation of New Cultivars: Newly selected lines are evaluated for yield, quality, disease resistance etc. Testing is done in research fields under ideal conditions, then in farmers' fields in different agro-climatic zones for at least three growing seasons. Finally certified and released as a new cultivar.

• Plant Breeding for Disease Resistance: Reduces dependence on fungicides and bactericides. Resistance can be genetic.

  • Breeding Methods: Conventional (hybridisation and selection), Mutation Breeding. Selection among somaclonal variants, Genetic engineering.
  • Sources of Resistance Genes: Cultivated varieties, germplasm collections, wild relatives.
  • Steps in Conventional Breeding for Disease Resistance: Screening germplasm for resistance sources, hybridisation of selected parents, selection and evaluation of hybrids, testing and release of new varieties.
  • Examples of Disease Resistant Varieties:
    • Wheat: Himgiri (Resistant to Leaf and Stripe rust, Hill bunt)
    • Brassica: Pusa Swarnim (Karan rai) (Resistant to White rust)
    • Cauliflower: Pusa Shubhra, Pusa Snowball K-1 (Resistant to Black rot and Curl blight black rot)
    • Cowpea: Pusa Komal (Resistant to Bacterial blight)
    • Chilli: Pusa Sadabahar (Resistant to Chilly mosaic virus, Tobacco mosaic virus and Leaf curl)
  • Mutation Breeding: Inducing mutations artificially using mutagens (chemicals or radiation like gamma rays) and then screening the plant population for desirable mutations (e.g., resistance). Example: Resistance to yellow mosaic virus in mung bean was induced by mutations. Resistance in Abelmoschus esculentus (bhindi) to yellow mosaic virus transferred from a wild species (A. manihot) resulted in a new variety called Parbhani kranti.

• Plant Breeding for Developing Resistance to Insect Pests: Insect infestation is a major cause of crop loss. Resistance may be due to morphological, biochemical, or physiological characteristics.

  • Examples of Resistance Traits: Hairy leaves (resistance to jassids in cotton, cereal leaf beetle in wheat), solid stems (resistance to stem sawfly in wheat), high aspartic acid, low nitrogen and sugar content (resistance to stem borers in maize), nectar-less cotton varieties (do not attract bollworms).
  • Breeding Steps: Similar to disease resistance breeding (screening, hybridization, selection, testing, release). Sources of resistance genes often found in cultivated varieties, germplasm, or wild relatives.
  • Examples of Pest Resistant Varieties:
    • Brassica (rapeseed mustard): Pusa Gaurav (Resistant to Aphids)
    • Flat bean: Pusa Sem 2, Pusa Sem 3 (Resistant to Jassids, aphids and fruit borer)
    • Okra (Bhindi): Pusa Sawani, Pusa A-4 (Resistant to Shoot and Fruit borer)

• Plant Breeding for Improved Food Quality (Biofortification): Breeding crops with higher levels of vitamins, minerals, or higher protein and healthier fats. A practical means to improve public health.

  • Objectives: Improve Protein content and quality; Oil content and quality; Vitamin content; Micronutrient and mineral content.
  • Examples:
    • Maize hybrids: Developed with twice the amount of amino acids lysine and tryptophan compared to existing hybrids.
    • Wheat: Atlas 66 variety, having high protein content, used as a donor for improving cultivated wheat.
    • Rice: Iron-fortified rice variety developed (contains >5 times more iron).
    • Vegetables (IARI, New Delhi): Vitamin A enriched carrots, spinach, pumpkin; Vitamin C enriched bitter gourd, bathua, mustard, tomato; Iron and Calcium enriched spinach and bathua; Protein enriched beans (broad, lablab, French, garden peas).

4. Single Cell Protein (SCP)
Refers to the edible biomass of microorganisms (like bacteria, yeasts, filamentous fungi, algae) grown on various substrates. An alternative protein source for human food and animal feed.

• Microorganisms Used: Spirulina (blue-green algae), Methylophilus methylotrophus (bacterium), Yeasts (Candida utilis).
• Substrates: Waste materials like agricultural wastes (straw, molasses), wood shavings, sewage, animal manure, even industrial effluents.
• Advantages:
  • Produces large quantities of protein-rich food in a short time (e.g., 250g microbe can produce 25 tonnes of protein/day).
  • Can be grown using inexpensive substrates, including waste materials, thus reducing pollution.
  • Reduces pressure on conventional agriculture (less land required).
  • Rich in protein, minerals, fats, carbohydrates, and vitamins.

5. Tissue Culture
Growing whole plants from any part of a plant (explant) taken out and grown in a test tube, under sterile conditions, in a special nutrient medium. Based on the principle of Totipotency (the capacity of a cell/explant to generate a whole plant).

• Technique: Requires a suitable nutrient medium (with carbon source like sucrose, inorganic salts, vitamins, amino acids, and growth regulators like auxins, cytokinins), sterile (aseptic) conditions. The explant grows and divides to form a callus (undifferentiated mass of cells), which then differentiates to form plantlets. These plantlets are transferred to soil to grow into mature plants.
• Micropropagation: Producing a large number of plants through tissue culture in a short duration. Each plant is genetically identical to the original plant (somaclones).
  • Advantages: Rapid multiplication of desired plants, production of disease-free plants, recovery of endangered species, propagation of plants that are difficult to grow by conventional methods.
  • Examples: Important food plants like tomato, banana, apple propagated this way.
• Recovery of Healthy Plants from Diseased Plants (Meristem Culture): The apical and axillary meristems are generally free of viruses even if the parent plant is infected. Meristems can be removed and grown in vitro under sterile conditions to obtain virus-free plants. Examples: Banana, sugarcane, potato.
• Somatic Hybridisation: Fusion of protoplasts (cells without cell walls) from two different varieties or species of plants to form a hybrid protoplast, which can be grown to form a new plant (somatic hybrid).
  • Process: Digesting cell walls using enzymes (cellulase, pectinase), isolating protoplasts, fusing desired protoplasts (e.g., using PEG - polyethylene glycol or electrofusion).
  • Example: Protoplasts of tomato and potato were fused to create Pomato. While it demonstrated the feasibility, the resulting plant did not have commercially desirable characteristics. Somatic hybridization holds potential for combining traits from species that cannot be hybridized conventionally.

Multiple Choice Questions (MCQs)

1. Which of the following breeding methods is useful for developing pure lines in cattle?
   a) Out-crossing
   b) Cross-breeding
   c) Inbreeding
   d) Interspecific hybridisation

2. MOET (Multiple Ovulation Embryo Transfer Technology) involves the use of which hormone to induce superovulation in cows?
   a) Progesterone
   b) LH (Luteinizing Hormone)
   c) FSH (Follicle Stimulating Hormone)
   d) Oxytocin

3. Hisardale, a new breed of sheep developed in Punjab, was achieved by:
   a) Out-crossing
   b) Mutation breeding
   c) Interspecific hybridisation
   d) Cross-breeding

4. 'Pusa Komal' is a disease-resistant variety of which crop, developed against bacterial blight?
   a) Wheat
   b) Cowpea
   c) Brassica
   d) Chilli

5. Biofortification aims to improve which of the following in crops?
   a) Resistance to pests
   b) Tolerance to drought
   c) Nutritional quality
   d) Yield quantity only

6. Spirulina is widely used as a source of:
   a) Single Cell Protein (SCP)
   b) Biofertilizer
   c) Biopesticide
   d) Industrial enzyme

7. The capacity of a plant cell or explant to generate a whole new plant is known as:
   a) Micropropagation
   b) Somatic hybridisation
   c) Totipotency
   d) Germplasm

8. Which part of a virus-infected plant is typically used in tissue culture to obtain virus-free plants?
   a) Mature leaves
   b) Root tips
   c) Flower buds
   d) Apical and axillary meristems

9. 'Pomato' was produced through which technique?
   a) Micropropagation
   b) Mutation breeding
   c) Somatic hybridisation
   d) Artificial insemination

10. Which of the following is NOT a primary objective of plant breeding?
    a) Increased yield
    b) Increased resistance to pathogens
    c) Decreased nutritional value
    d) Increased tolerance to environmental stress

Answer Key for MCQs:

1. c) Inbreeding
2. c) FSH (Follicle Stimulating Hormone)
3. d) Cross-breeding
4. b) Cowpea
5. c) Nutritional quality
6. a) Single Cell Protein (SCP)
7. c) Totipotency
8. d) Apical and axillary meristems
9. c) Somatic hybridisation
10. c) Decreased nutritional value

Remember to thoroughly revise these concepts, especially the examples of breeds, varieties, techniques, and their specific applications. Good luck with your preparation!