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Canada (158,426)
York University (12,360)
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BIOL 1001 (162)
Tamara Kelly (110)
Chapter 4

Chapter 4 summary

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York University
BIOL 1001
Tamara Kelly

EvolutionA change in allele frequencies 4 mechanisms that affect evolution in populations1 Natural selection increases the frequency of certain favourable traitsalleles 2 Genetic driftcauses alleletraits freq to change randomly 3 Gene flow occurs when individuals leave one popn join another and breed traits freq may alter due to new traits being introduced into the population and old traits being removed from previous population4 Mutation mutation modifies trait freq bu introducing new traits alleles changed by mutation may be beneficial or detrimental Evolutionary change occurs in populations natural selection acts on individualsNatural selection is the only mechanism of the 4 that alone can result in adaptationMutation gene flow and genetic drift do not favour certain alleles over othersMutation and genetic drift introduce a nonadaptive component into evolution1 Analyzing chance in allele frequencies The HardyWeinberg Principle2 Types of Natural SelectionGenetic variation the number and relative frequency of alleles that are present in a particular population Purifying selection when disadvantageous alleles decline in frequencyFitness tradeoff when one cause of directional selection on a trait is counterbalanced by a different factor that causes selection in the opposite
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