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10 Cards in this Set
- Front
- Back
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Tribolite
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Small, hard-shelled organisms that crawled and sometimes swam through the water. They are considered to be index fossils.
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Geologic time scale
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The division of Earth's history makes up the geologic time scale.
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Eons
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The longest subdivisions, these are based upon the abundance of fossils.
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Eras
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The second longest subdivisions, these are marked by major, striking, and worldwide changes in the types of fossils present.
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Periods
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Eras are subdivided into these. They are units of geologic time characterized by the types of life existing worldwide at the time.
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Epochs
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Periods can be divided into smaller units called epochs. They are characterized by differences in life-forms.
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Organic evolution
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The gradual change in species over geologic time
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Species
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A group of organisms that normally reproduces only with members of their group
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Natural selection
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A process that states organisms with characteristics that are suited to a certain environment have a better chance of surviving and reproducing than organisms that do not have these characteristics
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Pangaea
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Pangaea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras, forming approximately 300 million years ago
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