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biological species concept

definition of a species as a population or group of populations whose members can breed with one another in nature and produce fertile offspring


major biological changes evident in the fossil record


formation of new species

reproductive isolation

condition in which a reproductive barrier keeps two species from interbreeding

geographic isolation

separation of populations as a result of geographic change or migration to geographically isolated places

adaptive radiation

evolution from a common ancestor of many species adapted to diverse environments

punctuated equilibrium

evolutionary model suggesting species often diverge in spurts of relatively rapid change, followed by long periods of little change


study of multicellular organisms as they develop from fertilized eggs to fully formed organisms

geologic time scale

Earth's history organized into four eras: Precambrian, Paleozoic, Mesozoic, and Cenozoic

radiometric dating

determination of absolute ages of rocks and fossils through calculations based on a radioactive isotope's fixed rate of decay


time it takes for 50 percent of a radioactive isotope sample to decay

continental drift

motion of continents about Earth's surface on plates of crust floating on the hot mantle

mass extinction

episode of great species loss


identification, naming, and classification of species


two-part Latin name of a species

phylogenetic tree

branching diagram, suggesting evolutionary relationships, that classifies species into groups within groups

convergent evolution

process in which unrelated species from similar environments have adaptations that seem very similar

analogous structures

similarities among unrelated species that result from convergent evolution

derived character

homologous characteristic that unites organisms as a group


phylogenetic tree constructed from a series of two-way branch points, suggesting ancestral relationships among species

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