| Term | Definition |
|---|
| microevolution | evolutionary change on its smallest scale |
| population genetics | the study of how populations change genetically over time |
| modern synthesis | a comprehensive theory of evolution that integrated ideas from many other fields |
| population | a localized group of individuals that are capable of interbreeding and producing fertile offspring |
| gene pool | the aggregate of genes in a population at any one time is called the population's ______ _______ |
| Hardy-Weinberg theorem | states that the frequencies of alleles and genotypes in a population's gene pool remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work |
| Hardy-Weinberg equilibrium | the condition describing a non-evolving population, which follows these 5 conditions: large population, no gene flow, no mutations, random mating, no natural selection |
| mutations | change in the nucleotide sequence of DNA |
| genetic drift | similar deviations from the expected result explain how allele frequencies can fluctuate unpredictably from one generation to the next |
| bottleneck effect | when a sudden change in the environment may drastically reduce the size of a population, the survivors may have passed through a restrictive "bottleneck", and their gene pool may no longer be reflective of the original population's gene pool |
| founder effect | when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool isn't reflective of the source population |
| gene flow | genetic additions to and/or subtractions from a population resulting from the movement of fertile individuals or gametes |
| phenotypic polymorphism | a population is said to display ________ ________ for a character if two or more distinct morphs are each represented in high enough frequencies to be readily noticeable |
| average heterozygosity | the percent, on average, of a population's loci that are heterozygous in members of the population |
| geographic variation | differences between the gene pools of separate populations or population subgroups |
| cline | a graded change in a trait along a geographic axis |
| fitness | the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals |
| relative fitness | the contribution of a genotype to the next generation comparted to the contributions of alternative genotypes for the same locus |
| directional selection | __________ ________ is most common when a population's environment changes or when members of a population migrate to a new habitat with different environmental conditions from their former one |
| disruptive selection | ________ ________ occurs when conditions favor individuals on both extremes of a phenotypic range over individuals with intermediate phenotype |
| stabilizing selection | _________ _________ acts against extreme phenotypes and favors intermediate variants |
| balancing selection; balanced polymorphism | _________ ________ occurs when natural selection maintains stable frequencies of two or more phtnotypic forms in a population, a state called ___________ _________ |
| heterozygote advantage | if individuals who are heterozygous at a particular gene locus have greater fitness than the homozygous, natural selection will tend to maintain two or more alleles at that locus |
| frequency-dependent selection | the fitness of any one morph that declines if it becomes too common in the population |
| neutral variation | some of the genetic variation in populations probably has little or no impact on reproductive success, and thus natural selection doesn't affect those alleles |
| pseudogenes | genes that have become inactivated by mutations |
| sexual selection | natural selection for mating success |
| sexual dimorphism | marked differences between the sexes in secondary sexual characteristics, which are not directly associated with reproduction |
| intrasexual selection | (selection "within the same sex") is a direct competition amon individuals of one sex for mates of the opposite sex |
| intersexual selection | individuals of one sex (usually females) are choosy in selecting their mates from the other sex |
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