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Period: to
Precambrian
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Earth's surface is cool enough for liquid water.
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Earth's atmosphere starts to become oxygen rich.
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Continental sheilds appear.
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Fossils are rare.
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First known multicellular life appears.
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Stromatolites are the most common organism.
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First fungi appear.
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Period: to
Paleozoic
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Cambrian
Shelled marine invertebrates appear; trilobites and brachiopods are common. First vertebrates appear. -
Pennsylvanian Period
Giant cockroaches and dragonflies are common; coal deposits form; reptiles appear -
Orodovician
Echinoderms appear; brachiopods increase; trilobites decline; graptolites flourish; atmosphere reaches modern O2-rich state. -
Silurian
Eurypterids, land plants and animals appear. -
Mississippian Period
Amphibians flourish; brachiopods are common in oceans; and forests and swamps cover most land. -
Devonian
Age of fishes begins; amphibians appear; and gaint horsetails, ferns, and seed-bearing plants develop. -
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Period: to
Mesozoic
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Triassic
Dinosaurs appear; ammonites are common; cycads and conifers are abundant; and mammals appear. -
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Jurassic
Dinosaurs are the dominant life form; primitive birds and flying reptiles appear. -
Cretaceous
Flowering plants and modern birds appear; mass extinctions mark the end of the Mesozoic Era -
Paleocene
Age of mammels begins; first primates begin -
Period: to
Cenozoic
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Eocene
Horses, flying squirrels, bats. and whales appear -
Oligocene
Deer, pigs camels, cats, and dogs appear -
Miocene
Grazing heards are abundant; raccoons and wolves appear. -
Pliocene
Large carnivores appear
