BLG 316 Lecture Notes - Lecture 3: Allele Frequency, Genetic Drift, Sexual Selection
19 Apr 2019
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Document Summary
Genetic drift - random fluctuations in allele frequencies. In a small sample size when one allele frequency is lowered drastically (traumatically reducing the population) eventually they may cease to exist. Example: cheetahs have extreme genetic similarity as a result of bottleneck effect. Natural selection - only this results in adaptations in populations. Normal bell curve frequency of phenotype is in a median change in enviro shifts the median over in 1 direction. Natural selection can only select for heritable traits. # of seeds went down during drought, of the seeds that were left were hard/large. Therefore the selected individuals had large beaks unequal mortality due to fitness advantage. Median phenotype doesn"t do well in changed habitat bell curve is disrupted. For example: there are only hard or soft seeds and no middle ground so extreme phenotypes are selected. Heritable characteristics that might not intuitively seem to be a fitness advantage.
