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