The Evolution of Population
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Fighting4myown on September 11, 2011
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chapter 23
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24 terms
Terms | Definitions |
|---|---|
 microevolution | defining evolution on its smallest scale by focusing on evolutionary change in populations |
| genetic variation | differences among individuals in the composition of their genes or other DNA segments |
| average heterzygosity | the average percentage of loci that are heterozygous |
| geographic variation | differences in the genetic composition of separate populations |
| cline | a graded change in a character along a geographic axis |
| population | a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring |
| gene pool | all copies of every type of allele at every locus in all members of the population |
| hardy-weinberg principle | the gene pool of a population that is not evolving; named for the British mathematician and German physician who independently derived it in 1908 |
| genetic drift | chance events can also cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations |
| founder effect | when a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population |
| bottleneck effect | a population that passes through a "bottleneck" resulting in a severe drop in population size |
| gene flow | the transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes |
| relative fitness | the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals |
| directional selection | occurs when conditions favor individuals exhibiting one extreme of a phenotypic range, thereby shifting a population's frequency curve for the phenotypic character in one direction of the other |
| disruptive selection | occurs when conditions favor individuals at both extremes of a phenotypic range over individuals with intermediate phenotypes |
| stabilizing selection | acts against both extreme phenotypes and favors intermediate variants |
| sexual selection | a form of selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates |
| sexual dimorphism | a difference between the two sexes in secondary sexual characteristics |
| intrasexual selection | selection within the same sex, individuals of one sex compete directly for mates of the opposite sex |
| intersexual selection | (mate choice) individuals of one sex, usually the females, are choosy in selecting their mates from the other sex |
| neutral variation | differences in DNA sequences that do not confer a selective advantage or disadvantage |
| balancing selection | : occurs when natural selection maintains two or more forms in a population |
| heterozygote advantage | if individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygotes |
| frequency-dependent selection | the fitness of a phenotype depends on how common it is in the population |
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