Summary:
- Species go extinct when all of the individuals die out or evolve into a different species.
- Mass extinctions are caused by collisions with comets or asteroids, massive volcanic eruptions, or rapidly changing climate.
- After a mass extinction, many habitats are no longer inhabited by organisms because they have gone extinct.
- With new habitats available, some species will adapt to the new environments.
- Many new species evolve to fill those available habitats.
- At the end of this period of rapid evolution, life forms do not look much like the ones that were around before the mass extinction.