| A | B |
|---|
| evolution | change over time; the process by which modern organisms have descended from ancient organisms |
| theory | a well-supported testable explanation of phenomena that have occured in the natural world |
| fossil | preserved remains of ancient organisms |
| artifical selection | nature provides the variation and humans selected those variations that they found useful |
| struggle for existence | members of each species compete regularly to obtain food, living space, and other necessities of life |
| fitness | the ability of an individual to survive and reproduce in its specific environment |
| adaptation | any 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 | Darwin used this term to refer to the survival of the fittest |
| descent with modification | each living species has descended, with changes, from other species over time |
| common descent | the principle that states that all species were derived from common ancestors |
| homologous structure | structure that has different mature forms but develop from the same embryonic tissues |
| vestigial organ | the organs of many animals that are so reduced in size that they are just vestiges, or traces, of homologous organs in other species |
