variation is the differences in the characteristics of individuals in a population
variation may be due to differences in the genes inherited, the conditions in which organisms develop or a combination of the genes and the environment.
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B13.2: Evolution by Natural Selection
the theory of evolution by natural selection states that all species of living things have evolved from simple life forms that first developed over 3 billion years ago.
mutations occur continuously. very rarely, a mutation leads to a new phenotype. if the new phenotype is suited to an environmental change, it can lead to a relatively rapid change in the species.
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B13.3: Selective Breeding
selective breeding is a process where humans breed plants and animals for desired characteristics.
desired characteristics include:
disease resistance
increased food production in animals and plants
domestic dogs with a gentle nature
heavily scented flowers
problems can occur with selective breeding including defects in some animals due to lack of variation.
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B13.4: Genetic Engineering
crops that have had their genes modified are called GM crops. GM crops often have improved resistance to insect attack or herbicides and generally produce a higher yield.
genes can be transferred to the cells of animals and plants at an early stage of development and develop the desired characteristics. this is called genetic engineering.
in genetic engineering, genes from the chromosomes of humans and other organisms can be cut out using enzymes and transferred to the cells of bacteria and other organisms using a vector, which is usually a bacterial plasmid or a virus.
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B13.5: Ethics of Genetic Technologies
modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders.
there are benefits and risks assoiated with genetic engineering in agriculture and medicine.
some people have ethical objections to genetic engineering.
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