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10 Cards in this Set
- Front
- Back
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Trilobite
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Organism with a three-lobed exoskeleton that was abundant in Paleozoic oceans and is considered to be an index fossil.
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Geologic Time Scale
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Divisions of Earth's history into time units based largely on the types of life-forms that lived only during certain periods.
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Period
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Third-longest division of geologic time; is subdivided into epochs and is characterized by the types of life that existed worldwide.
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Eon
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Longest subdivision in geologic time scale that is based on the abundance of certain types of fossils and is subdivided into eras, periods, and epochs.
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Organic Evolution
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Change of organisms over geologic time.
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Species
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Group of organisms that reproduces only with other members if their own group.
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Natural Selection
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Process by which organisms that are suited to a particular environment are better able to survive and reproduce than organisms that are not.
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Pangaea
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Supercontinent formed at the end of the Paleozoic Era when sea level dropped and continents came together to form one giant landmass.
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Era
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Second-longest division of the geologic time scale; is subdivided into periods and is based on major worldwide changes in types of fossils.
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Epoch
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Next-smaller division of geologic time after the period; is characterized by differences in life-forms that may vary regionally.
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