| A | B |
|---|
| species | A group of similiar organisms that can mate with each other and produce fertile offspring. |
| fossil | The preserved remains or traces of an organism that lived in the past. |
| adaptation | A trait that helps an organism survive and reproduce. |
| evolution | The gradual change in a species over time. |
| scientific theory | A well tested concept that explains a wide range of observations. |
| natural selection | The process by which individuls that are better adapted to their environment are more likely to survive and reproduce than other members of the same species. |
| variation | Any difference between individuals of the smae species. |
| petrified fossil | Fossils that are formed when minerals replace the remains, changing them into rock. |
| mold | A hollow space in sediment in the shape of an organism or part of an organism. |
| cast | A copy of the shape of the organism the made the mold. |
| homologous structures | Similiar structures that related species have inherited from a common ancestor. |
| branching tree | A diagram that shows how scientists think different groups of organisms are related. |
| fossil record | The millions of fossils that scientists have collected. |
| extinct | A species with no members of that species that are still alive. |
