When did the first mass exinctions occur

Options

A. Devonian-silurian
B. Permian-triassic
C. Jurassic
D. Jurassic-cretaceous.

Answer

**Step-by-Step Text Solution:**

1. **Understanding Mass Extinctions**: Mass extinctions are significant events in Earth's history where a substantial number of species die out in a relatively short period. There have been five major mass extinctions recognized by scientists.

2. **Identifying the First Mass Extinction**: The first mass extinction event is known as the Ordovician-Silurian Extinction. This event occurred approximately 440 million years ago.

3. **Details of the Ordovician-Silurian Extinction**: During this extinction, a significant number of marine organisms, particularly small marine life, faced extinction due to environmental changes.

4. **Listing Subsequent Mass Extinctions**: After the Ordovician-Silurian extinction, the following mass extinctions occurred:
- Devonian Extinction (365 million years ago)
- Permian-Triassic Extinction (250 million years ago) - the largest mass extinction
- Triassic-Jurassic Extinction (210 million years ago)
- Cretaceous-Tertiary Extinction (65.5 million years ago) - which led to the extinction of dinosaurs.

5. **Conclusion**: The first mass extinction occurred during the Ordovician period, approximately 440 million years ago.

**Final Answer**: The first mass extinction occurred 440 million years ago during the Ordovician-Silurian period.

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