| Term | Definition |
|---|
| adaptation | the process by which, as a result of natural selection, organisms become better matched to their environment; also, a specific feature that makes an organism more fit |
| biogeography | the study and interpretation of distribution patterns of living organisms around the world |
| bottleneck effect | a change in allele frequencies of a population caused by a sudden reduction in population size (often due to famine, disease, or rapid environmental disturbance) |
| convergent evolution | a process of natural selection in which features of organisms not closely related come to resemble each other as consequences of similar selective forces |
| differential reproductive success | the situation in which individuals have greater reproductive success than other individuals in a population |
| directional selection | selection that, for a given trait, increases fitness at one extreme of the phenotype and reduces fitness at the other, leading to an increase or decrease in the mean value of the trait |
| disruptive selection | selection that, for a given trait, increases fitness at both extremes of the phenotype distribution and reduces fitness at middle values |
| evolution | a change in allele frequencies of a population |
| fitness | a relative measure of the reproductive output of an individual with a given phenotype compared with the reproductive output of individuals with alternative phenotypes |
| fixation | the point at which the frequency of an allele in a population is 100% and, therefore, there is no more variation in the population for this gene |
| fossil | the remains of an organism, usually its hard parts such as shell, bones, or teeth, which have been naturally preserved |
| founder effect | a change in the allele frequencies of a population resulting from the isolation of a small subgroup of a larger population |
| gene flow | a change in the allele frequencies of a population due to movement of some individuals of a species from one population to another, changing the allele frequencies of the population they join; also known as migration |
| genetic drift | a random change in allele frequencies over successive generations; a cause of evolution |
| heritability | the transmission of traits from parents to offspring via genetic information; also known as inheritance |
| homologous structures | body parts in different organisms that, although modified extensively over time to serve different functions in different species, are due to inheritance from a common evolutionary ancestor |
| inheritance | the transmission of traits from parents to offspring via genetic information; also known as heritability |
| migration | an agent of evolutionary change caused my the movement of individuals into or out of a population |
| mutagen | an agent capable of causing a mutation in DNA; may be chemical or physical |
| mutation | an alteration in the base-pair sequence of an individual's DNA; may arise spontaneously or following exposure to a mutagen |
| natural selection | a mechanism of evolution that occurs when there is a heritable variation for a trait and individuals with one version of the trait have greater reproductive success than do individuals with a different version of that trait |
| population | a group of organisms of the same species living in a particular geographic region |
| radiometric dating | a method of determining both the relative and the absolute ages of objects such as fossils by measuring both the radioactive isotopes they contain, which are known to decay at a constant rate, and their decay products |
| sexual selection | the process by which natural selection favors traits, such as ornaments or fighting behavior, that give an advantage to individuals of one sex in attracting mating partners |
| stabilizing selection | selection that, for a given trait, produces the greatest fitness at the intermediate point of the phenotypic range |
| trait | any characteristic or feature of an organism |
| vestigial structure | a body part, once useful to organisms but which has lost its function over evolutionary time; the human appendix and molars in bats that now consume an exclusively liquid diet |
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