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Natural Selection

Natural Selection. Natural Selection. Natural selection operates on the phenotypes of individuals, produced by their particular combinations of alleles. Some allele combinations are perpetuated at the expense of other genotypes.

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Natural Selection

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  1. Natural Selection

  2. Natural Selection • Natural selection operates on the phenotypes of individuals, produced by their particular combinations of alleles. • Some allele combinations are perpetuated at the expense of other genotypes. • This differential survival of some genotypes over others is called NATURAL SELECTION.

  3. Stabilising Selection • Maintains the population in a stable form, as it favours the average phenotype at the expense of the extreme in either direction • EG: The birth weights of humans remains in the 3-4 kg range. • See Page 104 BIOZONE.

  4. Directional Selection • Favours the phenotype of one extreme over the average or the other extreme. • EG: the increase in the dark form of the peppered moth due to the darker bark on trees during the Industrial Revolution.

  5. Disruptive Selection • Favours both the extremes at the expense of the average.

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