BIOL 2040 Lecture Notes - Lecture 10: Foster Care, Stabilizing Selection, Genetic Variation
13 Feb 2016
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Document Summary
Ex. selecting for taller corn, breed from only tallest individuals to get next generation: this places a selection pressure on the population. Selection intensity (s) = avg selected avg all. Average of offspring is going to be between average of all the parent generation, and average of parents selected for. Directional: moves the average of the population in the direction. Stabilizing selection: selection favours an intermediate being selected for phenotype/trait/behaviour: ex. aphids live in galls on the sides of plants, galls are preyed on by parasitoid wasps, and birds. Birds more likely to go after large galls, while wasps lay their eggs in small galls. Causes selection for medium sized galls to prevent being spotted by birds, but also being too big for wasps. Diversifying/disruptive selection: intermediate types have the lowest fitness; selected against, while extremes are selected for o: ex. seedcrackers. Very big beaks and very small beaks selected for, medium beaks selected against.
