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Download 13.1 selective breeding
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13.1 selective breeding Breeding from the best plants or animals Farmers will choose • Dairy cattle that produce lots of milk • Tomato plants that produce a lot of tomatoes • Wheat that is resistant to a pest • http://www.bbc.co.uk/learningzone/clips/gen etic-engineering-to-increase-productivity-inrice/12911.html Breeding sheep • Choose depending on the products they wish to sell • Wool • Lean meat • Large number of offspring • Cheese – large milk yield Selective breeding • Takes several generations Pedigree dogs • Selectively bred • Have desired characteristics • suffer from health problems • Eg German Shepherd – sloping back – low back legs – causes hip problems Pedigree dogs • Pugs – snub nose causes breathing problems Pedigree dogs • Inbred • Bred with siblings • Lower life expectancy Selectively bred wheat • Grain that is turned into flour Wild wheat Modern wheat Small ears few seeds Large ears many seeds Brittle stalks ears fall off Strong stalks ears stay on Ears ripen at different times Ears ripen at the same time Stalks grow to different heights Stalks grow to the same height Modern crops • Easier to harvest • Bigger yield • Resistant to disease 3 mark question • Select • Breed • Repeat • You get the characteristics you want problems • Reduces the number of genes (gene pool) • Reduces variation • New disease could wipe out the whole crop • http://www.bbc.co.uk/schools/gcsebitesize/sc ience/add_gateway_pre_2011/living/genesrev 2.shtml
