Chapter 12 - Geologic Time and Concepts

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Geologic Time scale

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a time line of Earth’s past

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Theory

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assumptions or statements devised to explain an aspect of the natural world

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Hypothesize

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to make an assumption about something that is not positively known

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Eon

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the longest unit of geologic time

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Era

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a subdivision of a geologic eon

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Period

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a subdivision of a geologic era

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Epoch

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a subdivision of a geologic period

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Geographic Isolation

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the separation of a population of organisms from the rest of its species due to a physical barrier, such as a mountain range or an ocean

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Land Bridge

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land that connects two continents that were previously separated

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Mass Extinction

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the extinction of many species on Earth within a short period of time