EvolutionMechanisms160-page4 - move to an area isolated...

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Evolutionary Mechanisms - 4 Genetic drift tends to reduce variation within one population, but may increase genetic variation between different populations. Genetic drift includes the Population bottleneck in which some catastrophic event causing a "bottleneck" (drastic reduction in size of a large population caused by some unfavorable condition). The few survivors' genotypes will be the source of the subsequent generations. The world's Cheetah population today has a very small gene pool as a consequence of a unknown bottleneck event. The northern elephant seal, hunted almost to extinction, have a very uniform gene pool because of the 20 surviving seals in 1890, just one male fathered all offspring. In the Founder Effect a small number of individuals disperse or
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Unformatted text preview: move to an area isolated from the original population. The new population, with a small gene pool, will be established with a preponderance of a few genotypes. (like the bottleneck). The dispersed frequency will determine the character of the new population, which may differ significantly from the original population (which is how the founder effect differs from a bottleneck; in the bottleneck, the gene pool consists of the survivors from the original pool, rather than migrants). An example of this is the frequency of polydactyly in the Pennsylvania Dutch of the United States. Founder populations can lead to adaptive radiation in some environments....
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