| A | B |
|---|
| Evolution | change in a kind of organism over time; process by which modern organisms have descended from ancient organisms |
| Theory | well-tested explantion that unifies a broad tange of obsevations |
| Fossil | preserved remains or evidence of an ancient organism |
| Natural variation | differences among individual of a species |
| Artificial selection | selection by humans for breeding useful traits from the natural variation among different organisms |
| Struggle for existence | competition among members 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 | process by which individuals that are better suited to their environment survive and reproduce most successfully; also called natural selection |
| Natural selection | process by which individuals that are better suited to their environment survive and reproduce most successfully; also called survival of the fittest |
| 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 have different mature forms in different organisms but develop from the same embryonic tissues |
| Vestigal organ | organ that serves no useful function in an organism |
