| Term | Definition |
|---|---|
| fossil | the preserved remains or traces of an organism that lived in the past |
| species | a group of similar organisms that can mate with each other and produce fertile offspring |
| extinction | the process of every member of a species disappearing from Earth |
| behavioral adaptations | a thing that organisms do to survive in a particular environment, such as the way they feed, breed, or move |
| physical adaptations | a changing characteristic of an organism that enables it to survive in a particular environment; these changes usually happen gradually over generations |
| adaptation | behavioral or physical characteristic that allows an organism to survive in its environment |
| homologous structures | body parts that are structurally similar in related species; provide evidence that the structures were inherited from a common ancestor |
| natural selection | the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species |
| fitness | the ability of an organism to produce offspring that survive and reproduce |
