| A | B |
|---|
| geologic time scale | the division of Earth's history by the appearance or disappearance of types of organisms throughout history |
| eons | the longest subdivision based on the abundance of certain fossils |
| eras | marked by major, striking, and worldwide changes in the types of fossils present |
| periods | divide eras up into smaller units characterized by they types of life existing worldwide |
| epochs | divide periods up into smaller units characterized by the type of life existing from continent to continent |
| PreCambrian time | the longest period of Earth's history, 4.5 billion years ago |
| Paleozoic Era | era of ancient life |
| Pangea | the collision of the continents, forming one larger super continent |
| Mesozoic Era | era of middle life; the era dinosaurs existed |
| Cenozoic Era | era of recent life; the era humans exist; current era we are living now |
