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Unformatted text preview: increase due to limitation of number of nest holes. Consider prey switching in birds: mutation increases the fecundity of a moth. More caterpillars present, birds switch their search image and prey more heavily on the abundant caterpillars: reduces population size clearly the population is less fit. These examples have assumed that population size is some measure of average fitness May not be the case depending on the mode of selection: Soft versus hard selection . Soft selection is like grading on a curve: there are always a certain number of As (or F's). Regardless of the absolute fitness of individuals or the population the "better" ones will survive to fill those spots. Hard selection assumes some threshold level of "fitness" that could be set by the environment. If all individuals are below this level, population crashes; if all are above, population grows....
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- Fall '10