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17 Cards in this Set
- Front
- Back
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evolution
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the change in population of a species over time
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extinction
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the evolutionary termination of a species caused by the failure to reproduce and the death of all remaining members of the species; the natural failure to adapt to environmental change
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index fossil
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a fossil found in a narrow time range but widely distributed around the earth; used to date rock layers
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fossil
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evidence of a pastlife preserved in rock
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trace fossil
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a fossilized mark that is formed in soft sediment by the movement or actions of an animal
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absolute dating
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any method of measuring the age of an event or object in years. the actual age for a rock or mineral
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continental drift theory
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theory that states that the gradual shifting of Earth's plates causes continents to change their global positions over time
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Wegner
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German scientist that was adamently fascinated by plate techtonics. responsible for continental drift theory, and the theory of Pangaea
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half-life
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the time needed for half of a sample of radioactive substance to undergo radioactive decay
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law of superposition
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states that the oldest rock layers lie on the bottom and the youngest rocks are on top of any undisturbed sequence of sedimentary rocks
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radioactive decay
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the process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element
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relative dating
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uses information about rock layers and the fossil record to determine the age relationships between rocks
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unconformity
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gaps in the rock record
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era
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a unit of geologic time that includes two or more periods
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geologic time scale
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the standard method used to divide the Earth's long natural history into manageable parts
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mass extinction
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occurs when a large proportion of the earth's species go extinct in a relatively short period of time
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period
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a subdivision of the eras in geologic time
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