Summary:
- At the end of the Permian, nearly 95% of all marine species died off.
- 70% of land species became extinct.
- Moving from the seas to land required many adaptations.
- By the beginning of the Paleozoic, organisms evolved shells.
- Fish evolved jaws and many other adaptations for ocean life.
- Insects and spiders were already land dwellers by the time amphibians appeared.
- In the Cambrian Explosion, there was an explosion of life.
- This explosion was in number and in diversity.
- It is possible that multiple things went wrong at the same time.