• 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.
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