| A | B |
|---|
| species | A group of similar organisms whose members can mate with one another and produce fertile offspring. |
| adaptation | A characteristic that helps an organism survive in its environment or 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 individuals 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 same species |
| fossil | The preserved remains or traces of an organism that lived in the past. |
| sedimentary rock | A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together. |
| relative dating | A technique used to determine which of two fossils is older. |
| absolute dating | A technique used to determine the actual age of a fossil. |
| fossil record | The millions of fossils that scientists have collected. |
| extinction | A species that does not have any living members. |
| biodiversity | The number of different species in an area. |
| mutation | Inheritable changes in the DNA code. |
| habitat destruction | The loss of a natural habitat. |
| endangered species | A species in danger of becoming extinct in the near future. |
| threatened species | A species that could become endangered in the near future. |
| keystone species | A species that influences the survival of many other species in an ecosystem. |
