| A | B |
|---|
| species | a group of similar organisms that can mate and produce fertile offspring |
| 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 individuals that are better adapted to their environment are more likely to survive and reproduce |
| 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 plats and animals are pressed and cemented together |
| petrified fossil | a fossil in which minerals replace all or part of an organism |
| mold | a fossil formed when an organism buried in sediment dissolves, leaving a hollow area |
