| A | B |
|---|
| evolution | change in a kind of organism over time |
| evolution | process by which modern organisms have descended from ancient organisms |
| theory | a well-tested explanation that unifies a broad range of observations |
| hypothesis | possible answer to a scientific question |
| fossil | preserved remains or evidence of an ancient organism |
| artifical selection | selection by humans for breeding of useful traits from the natural variation among different organisms |
| struggle for existence | competition among mebers of a species for food, living space, and other necessities of life |
| fitness | ability of an organism to survive and reproduce in its environment |
| adaptation | inherited characteristic that increases an organism's chance of survival |
| survival of the fittest | natural selection |
| natural selection | process by which individuals that are better suited to their environment survive and reproduce most successfully |
| descent with modification | principle that each living species has descended, with changes, from other species over time |
| common descent | principle that all living things have a common ancestor |
| homologous structure | structures that develop from the same embryonic tissues but have different mature forms in different organisms |
| vestigial organ | organ that serves no useful function in an organism (ex., appendix) |
| modify | change |
| variation | differences |
| homologous structures | bat wings, whale flippers, and human hands |
