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200
Earth was formed 4.6 billion years ago.
The Earth was formed 4.6 billion years ago. -
201
Water was on Earth 3.8 billion years ago.
Earth's surface cooled enough for water to remain liquid. -
202
Rocks were formed 4 billion years ago.
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210
Photosynthetic bacteria began pumping oxygen 2.2 billion years ago.
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250
Ordovician Period 505-440 mil. yr. ago : Octopi, squid.
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250
Silurian Period 440-410 mil. yr. ago: Jawless fish, land plants.
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250
Devonian Period 410-360 mil. yr. ago: Insects. Age of Fishes.
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250
Carboniferous Period 360-290 mil. yr. ago: Reptiles.
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250
Cambrian Period 544-505 mil. yr. ago: Invertebrates, trilobites, brachiopods.
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300
Permian Period 290-245 mil. yr. ago: Reptiles.
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320
Triassic Period 245-208 mil. yr. ago: Dinosaurs.
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320
Jurrasic Period 208-145 mil. yr. ago: Age of Reptiles.
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320
Cretaceous Period 145-65 mil. yr. ago: Leafy trees, shrubs, small flowering plants. Mass extinction.
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400
Tertiary Period 65-1.8 mil. yr. ago: Marine mammals.
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400
Quaternary Period 1.8 mil. yr. ago-present: Humans.