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change over time; process by which modern organisms descended from ancient organisms


well-tested, well-supported explanation that unifies a broad range of observations


preserved remains of an ancient organism

natural variation

differences among individuals of a species; results from mutation and sexual reproduction

struggle for existence

competition between organisms for food and space


ability of an organism to survive and reproduce in its environment


inherited characteristic that increases an organism's chance of survival

survival of the fittest

individuals that are better suited to their environment survive and reproduce most successfully; natural selection

natural selection

individuals that are better suited to their environment survive and reproduce most successfully; survival of the fittest

homologous structure

structures that have different mature forms but develop from the same embryonic tissues

vestigial structure

organ so reduced in size, it does not serve an important function; may be homologous to structures in other organisms


two organisms that are so similar they can interbreed in nature and produce fertile offspring


formation of a new species as a result of reproductive isolation

reproductive isolation

separation of species that prevents them from interbreeding and producing fertile offspring

behavioral isolation

type of reproductive isolation in which two organisms have different mating rituals that prevent them from interbreeding

geographic isolation

type of reproductive isolation in which two populations are separated by geographic barries like mountains or bodies of water


variety of organisms that exist in the biosphere


classification of organisms

binomial nomenclature

two part scientfic name for an organism; its genus is listed first, followed by its species


first part of an organism's scientific name


second largest taxonomic group; there are six - animalia, plantae, protista, eubacteria, archaebacteria, fungi


most inclusive taxonomic group, larger than kingdom; three exist - bacteria, archaea, eukaryota


a single celled plant or animal, ex. amoeba, paramecia, euglena

divergent evolution

pattern of evolution in which two species become more and more dissimilar


kingdom of heterotrophs that obtain nutrients through absorption, ex. mushrooms, yeasts


domain of organisms that contain nuclei, includes animals, plants, fungi, and protists

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