Evolution by Natural Selection

3 genetic drift change in allele frequencies in a

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Unformatted text preview: roach .5 Frequencies will equal 1 P^2 + 2PQ + Q^2 = 1 For this principle to be held true, the four mechanisms cannot occur Random Mating must also occur Hardy- Weinberg can act as a null hypothesis when testing for occurrence of any of the 4 mechanisms of evolution 25.2: Types of Natural Selection Directional selection: changes the allele frequency of a particular trait in one direction Stabilizing selection: no change in allele frequency of the average value Disruptive selection: Favors extreme phenotypes and eliminates phenotypes of the average value Balancing Selection: Amount of phenotypes balances over type 25.3: Genetic Drift Change in allele frequencies in a population that is due to chance Is random Most pronounced in small populations Can lead to random loss or fixation of alleles One example: Hurricane causes green iguanas to end up on an island never before inhabited (Founder effect): when an organism inhabits a new geographic region and establishes a new population Bottleneck...
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