| A | B |
|---|
| era | The largest division of the earth’s history. The Precambrian, Paleozoic, Mesozoic, and Cenozoic eras are measured in millions of years. |
| geologic time | The time scale of the history of the earth and its life. |
| sedimentary rock | Rock formed from layered sediments that pile up and squeeze together,offering clues to the earth’s past. |
| fossil | Remains or traces of an organism that lived in the past. |
| extinct | Referring to forms of life that have died out. |
| fossil record | Record of life on earth provided by fossil. |
| mold | A fossil impression left in rock bt the hard parts of an organism. |
| cast | A fossil form by minerals in water that build up in mold. |
| primates | A member of a group of mammals that includes humans. This group appeared on earth more than 65 million years ago. |
| hominids | The primate ancestor of modern humans. |
