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| Population Genetics | The study of genetic changes in populations; the science of microevolutionary changes in populations |
| Modern Synthesis | A comprehensive theory of evolution emphasizing natural selection, gradualism, and populations as the fundamental units of evolutionary change; also called neo-Darwinism |
| Population | A group of individuals of one species that live in a particular geographic area |
| Species | A group whose members possess similar anatomical characteristics and have the ability to interbreed |
| Gene Pool | The total aggregate of genes in a population at any one time |
| Hardy-Weinberg Theorem | An axiom maintaining that the sexual shuffling of genes alone cannot alter the overall genetic makeup of a popultation |
| Hardy-Weinberg Equilrium | The condition describing a nonevolving population |
| Microevolution | A change in the gene pool of a population from generation to generation |
| Bottleneck Effect | Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer gentically representative of the original population |
| The Founder Effect | Genetic drift attributed to colonization by limited number of individuals from a parent population |
| Polymorphic | Reffering to a population in which two or more physical forms are present in readily noticeable frequencies |
| Natural Selection | Differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. |
| Gene Flow | The loss or gain of alleles in a population due to the migration of fertile individuals or gametes between populations |
| Mutation | A rare change in the DNA of a gene ultimately creating genetic diversity |
| Geographic Variation | Differences in genetic structure between populations |
| Cline | Graded variation in some traits of individuals that parallels a gradient in the enviornment |
| Balanced Polymorphism | The ability of natural selection to maintain diversity in a population |
| Heterozygote Advantage | Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools |
| Frequency-dependent selection | A decline in the reproductive success of a morph resulting from the morph's phenotype becoming too common in the population; a cause of balanced polymorphism in populations |
| Neutral Variation | Genetic diversity that confers no apparent selective advantage |
| Darwinian 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 one genotype to the next generation compared to that of alternative genotypes for the same locus |
| Directional Selection | Natural selection that favors individuals at one end of the phenotypic range |
| Diversifying Selection | Natural selection that favors extreme over intermediate phenotypes |
| Stabilizing Selection | Natural selection that favors intermediate variants by acting against extreme phenotypes |
| Sexual Dimorphism | A special case of polymorphism based on the distinction between the secondary sex characteristics of males and females |
| Intrasexual Selection | A direct competition among individuals of one sex for mates of the opposite sex |
| Intersexual Selection | Individuals of one sex (usually females) are choosy in selecting their mate from individuals of the other sex |
