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ch 7.1
| Term | Definition |
|---|---|
| eon | largest units of of geologic time |
| era | eons are subdivided into smaller units of time |
| periods | eras are subdivided into this |
| epochs | periods are subdivided into this |
| mass extinction | the extinction of many species on earth within a short period of time |
| land bridge | connects the two continents that were previously seperated |
| geographic isolation | the separation of a population of organisms from the rest of its species due to some physical border |