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3
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found in earth's first atmosphere
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4
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a fossil that forms when the impression of an organism fills with sediments
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8
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the most common fossils in rocks of the last 500 million years
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9
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the study of fossils of animal and plant life that existed in remote geological times
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10
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a hollow area in sediment in the shape of all part of an organism
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11
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the earliest multi celled organisms
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12
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trilobites abundant, fish abundant, and pangaea forms
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13
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a fossil of a species that existed in a short time in history
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14
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uses special scientific instruments to determine the actual age of the rock
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16
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measuring the amount of a radioactive isotope and decay
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17
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the geologic time scale is subdivided into
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18
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first abundant mammals and birds
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19
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pangaea breaks up, dinosaurs abundant. and ancient birds found
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20
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the period of geologic time that has occurred most recently
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