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Fossils show that life on Earth started around 3.5 million years ago.
False
Humans appeared on Earth around 200,000 years ago.
True
Almost all known fossils come from the oldest eon, the Phanerozoic.
False
Mass extinctions occur when large numbers of species die out over a long period of time.
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The geologic time scale is divided into eons, eras, periods, and epochs.
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Land plants and fish appeared in Earth's early history.
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The sudden disappearance of many fossil species followed by the sudden appearance of new species marks a mass extinction.
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A period is a block of time during which unique rock layers were laid down.
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The Precambrian consists of three eras and includes most of Earth's history.
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The Cambrian explosion marks the beginning of the Cenozoic era.
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The Proterozoic Eon ended with the appearance of many new life-forms.
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Humans have found more fossils from the Mesozoic era than from the Cenozoic era.
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