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Extinction
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Lecture 11
3/2/98
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| | Last week we discussed how the diversity of life expands through evolution. |
| | Today we will look at extinctions, where the diversity of life diminishes. |
| | Extinctions are a common occurence in the geologic past. |
| | Extinctions are the result of biologic and earth processes. |
| | Mass Extinctions form the boundaries of geologic time units |
| | Mass extinctions typically open environments for new groups to exploit and radiate into. |
| Major Mass Extinctions through Geologic Time |
| | Cambrian-Ordovician boundary (510 MY) |
| | Ordovician-Silurian boundary (440 MY) |
| | Devonian-Carboniferous boundary (360 MY) |
| | Permian-Triassic boundary (245 MY) |
| | 90% of life forms become extinct |
| | Triassic-Jurassic boundary (208 MY) |
| | Cretaceous-Tertiary boundary (65 MY) |
| Causes of Mass Extinctions |
| | Reduction in food resources |
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