| A | B |
|---|
| Cenozoic Era | the most recent geologic era, beginning 65 million years ago; the Age of Mammals |
| epoch | subdivision of a geologic period |
| era | largest unit of geologic time |
| geologic column | arrangement of rock layers based on the ages of the rocks |
| invertebrate | animal without a backbone |
| Mesozoic Era | geologic era that lasted from 248 million to 65 million years ago; the Age of Reptiles |
| Paleozoic Era | geologic era that followed Precambrian time, lasting from 540 million to 248 million years ago |
| period | subdivision of a geologic era |
| Precambrian time | earliest and longest geologic era, lasting from 4.6 billion to 540 million years ago |
| theory of evolution | theory that organisms change over time and that new organisms are derived from ancestral types |
| vertebrate | animal with a backbone |
