BIOL 1001 Chapter 4: Evolutionary Processes

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5 Feb 2016
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Two fundamental messages of this chapter: natural selection is not the only agent responsible for evolution, and each of the four processes have different consequences. Under these conditions, the genotypes a1a1, a1a2, a2a2 should be in the hardy- Weinberg proportions p2 +2pq+q2, respectively, and no evolution will occur. If the observed data is different from the expected data it would mean that one or more of the mechanisms are at work. Natural selection occurs when individuals with certain phenotypes produce more offspring than offspring with other phenotypes do. If certain alleles associated with favored phenotype, they increase in frequency. Lack of genetic variation in a population is a bad thing for natural selection. Stabilizing selection: selection reduced phenotypes at both extremes in a population, there is no change in average value of trait, and genetic variation decreases, ex. Very large and very small babies are most likely to die, leaving narrow distribution of birth weights.

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