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Ch 4: Geologic Time
| Term | Definition |
|---|---|
| species | Group of organisms that only reproduce with members of their own group |
| cyanobacteria | Earliest form of life. Blue-green algae that photosynthesized. |
| gymnosperm | Plants that produce seeds but not flowers. |
| angiosperm | Plants that have flowers |
| geologic time scale | Divisions of earth's history into time units |
| trilobite | Index fossil that has three lobes, and a segmented body |
| pangaea | large, ancient landmass that contained all continents. Formed in the Paleozoic and broke up in the Mesozoic. |
| Cenozoic | Era of recent life. Began 66 million years ago. |
| Paleozoic | Era of ancient life; dominated by fish and ended with a great mass extinction |
| Precambrian | Longest time of earth's history. Lasted nearly 4 billion years. |
| Mesozoic | Era of middle life. Pangaea broke apart, dominated by reptiles & dinosaurs. |
| organic evolution | Changes of organisms over time |
| eon | longest subdivision of geologic time |
| era | second longest subdivision of geologic time, based on worldwide fossil changes. |
| period | These subdivisions are divided into epochs |
| epoch | smallest division of geo time. |
| natural selection | Process by which only the organism that are suited for an environment will survive. "Survival of the fittest" |