Unit 4: Agriculture - Manipulation of Food Species (Sexual Reproduction)

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  • Manipulation of Food Species - Sexual Reproduction
    • Selective Breeding - exaggerate a single desirable characteristic or combine several
      • Bulls - high meat:fat ratio and high gross productivity
      • Crops - high nutrient, strong stem, pest/weather resistance, appealing to the eye and good taste
      • Dairy cows - high milk production and low fat content in milk
      • Crossbreeding between breeds used - reduces problems of inbreeding
        • Hybrid vigour - good health produced by breeding non-closely related varieties
        • Heterosis - hybrid vigour produced by breeding non-closely related organisms
    • Artificial Insemination - sperm from desirable bull inserted into a female
      • Many cows can be fertilised by one bull
      • Desirable traits maintained after bull's death
      • Cow breeding synchronised, allowing easier herd management
      • Reduces genetic diversity
    • Embryo Transfer - cow treated with FSH producing more eggs then artificial insemination or fertilised eggs are removed and frozen
      • Able to choose cow's sex
      • Used to produce multiple offspring
    • The Green Revolution - high yielding cereal varieties selectively bred
      • Variety IR8 had short, stiff stems and a higher biomass
        • Increased harvests and reduced famine problems
      • Only farmers who could afford seeds were able to grow crop
        • Poorer farmers did not benefit and lost their farms due to lack of funds
        • Poor farmers unable to work on other farms due to machinery replacements


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