Summary:
- The Phanerozoic Eon is divided into three eras—the Paleozoic, the Mesozoic and the Cenozoic.
- They span from about 540 million years ago to the present.
- Life gradually became more diverse and new species appeared.
- Most modern organisms evolved from species that are now extinct.
- Some organisms survive changes in the climate.
- Others go extinct when the climate changes too much.
- Earth’s climate has gone through four cycles of frigid glaciers and warm tropical seas.
- The quantity and diversity of life has exploded since the beginning of the Phanrozoic.