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Chapter 20

"Genes Within Populations" Evolutionary Biology, BIO 152 CSU Chico

inheritance of acquired characteristics changes that individuals acquired during their lives were passed on to their offspring.
population genetics the study of the properties of genes in populations
the requirements to be in Hardy-Weinberg equilibrium no mutation, no genes are transferred to or from other sources, mating is random, population size is very large, no selection occurs.
gene flow the movement of alleles from one population to another
assortive mating phenotypically similar individuals mate
genetic drift frequencies of particular alleles may change drastically by chance alone
founder effect one or a few individuals disperse and become the founders of a new, isolated population at some distance from their place of origin
bottleneck effect populations may be drastically reduced in size, this may result from flooding , drought, epidemic disease, and other natural forces, or from changes in the environment
fitness quantify reproductive success
frequency-dependent selection the fitness of a phenotype depends on its frequency within the population
oscillating selection favors one phenotype at one time and another phenotype at another time
heterozygote advantage favors individuals with copies of both alleles and thus works to maintain both alleles in the population
disruption selection selection acts to eliminate intermediate types
directional selection selection acts to eliminate one extreme from an array of phenotypes, the genes promoting this extreme become less frequent in the population and may eventually disappear
stabilizing selection selection acts to eliminate both extremes from an array of phenotypes, increasing the frequency of the already common intermediate type
assortive mating a. affects genotype frequencies expected under Hardy-Weinberg Equilibrium b. affects allele frequencies expected under Hardy-Weinberg equilibrium c.has no effect on the genotypic frequencies expected under Hardy-Weinberg a. affects genotype frequencies expected under Hardy-Weinberg Equilibrium
relative fitness a. refers to the survival rate of one phenotype compared to that of another b.refers to the reproductive success of a phenotype d. none a. refers to the survival rate of one phenotype compared to that of another



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