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24 Cards in this Set
- Front
- Back
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Microevolution
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Evolutionary change below the species level; change in the allele frequencies in a population over generations.
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Genetic variation
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Differences among individuals in the composition of their genes or other DNA segments.
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Average heterozygosity
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The percentage, on average, of a population’s loci that are heterozygous in members of the population.
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Geographic variation
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Differences between the gene pools of geographically separate populations or population subgroups.
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Cline
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A graded change in a character along a geographic axis.
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Population
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A group of individuals of the same species that live in the same area and interbreed, producing fertile offspring.
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Gene pool
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The aggregate of all copies of every type of allele at all loci in every individual in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population.
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Hardy-Weinberg principle
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The principle that frequencies of alleles and genotypes in a population remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.
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Genetic drift
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A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in small populations.
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Founder effect
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Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.
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Bottleneck effect
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Genetic drift that occurs when the size of a population is reduced, as by a natural disaster or human actions. Typically, the surviving population is no longer geneti- cally representative of the original population.
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Gene flow
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The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes.
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Relative fitness
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The contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population.
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Directional selection
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Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than do other individuals.
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Disruptive selection
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Natural selection in which individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes.
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Stabilizing selection
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Natural selection in which intermediate phenotypes survive or reproduce more successfully than do extreme phenotypes.
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Sexual selection
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A form of selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.
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Sexual dimorphism
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Differences between the secondary sex characteristics of males and females.
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Intrasexual selection
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Selection in which there is direct competition among individuals of one sex for mates of the opposite sex.
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Intersexual selection
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Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.
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Neutral variation
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Genetic variation that does not provide a selective advantage or disadvantage.
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Balancing selection
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Natural selection that maintains two or more phenotypic forms in a population.
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Heterozygote advantage
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Greater reproductive success of heterozygous individuals compared with homozygotes; tends to preserve variation in a gene pool.
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Frequency-dependent selection
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Selection in which the fitness of a phenotype depends on how common the phenotype is in a population.
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