Geologic Time Scale

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Scientists use radioactive dating techniques to estimate the age of an Earth material.

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the age of an Earth material.

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In what time did Pangaea, the supercontinent, appear? Options: Mesozoic Era, Cenozoic Era, Paleozoic Era, Precambrian Time

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Paleozoic Era

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Scientists found a fossil of a horse, fossil X, in a shallow rock layer. In a much deeper rock layer, they found fossil Y, which was a fossil from an animal that closely resembled a horse but was the size of a dog. Based on this explanation, what is the best explanation for these findings?

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The animal that formed fossil y is a distant relative of fossil X.

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Mason claims, "Gastropods are index fossils." Clara disagrees. Which of the following best supports Clara's disagreement?
- To be classified as an index fossil, the fossil must be unique. Since the gastropod is not unique, it cannot be an index fossil.
- An index fossil must be found over a wide area of the Earth. Since the gastropod is widely spread, it cannot be an index fossil.
- To be an index fossil, the fossil of the organism must be found in many rock layers. Since the gastropod is not found in every layer, it cannot be an index fossil.
- If a fossil is to be considered an index fossil, the organism must have lived only a short period of time. Since the gastropod lived a long period of time it is not an index fossil.

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If a fossil is to be considered an index fossil, the organism must have lived only a short period of time. Since the gastropod lived a long period of time it is not an index fossil.

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What other evidence have scientists most likely found that helped them determine that mammoths lived after triceratops became extinct?

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Fossils of triceratops have been found only in rock layers that are deeper than mammoth fossils.

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Analysis of rock strata and the fossil record provide

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relative dates.

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In which time period are we currently living? Options: Cenozoic Era, Precambrian Time, Mesozoic Era, Paleozoic Era

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Cenozoic Era

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Dinosaurs, small mammals, and birds appeared in this time period.

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Mesozoic Era

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Which time period is the longest? Mesozoic Era, Cenozoic Era, Paleozoic Era, Precambrian Time

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Precambrian Time

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In what time period did jellyfish first appear?

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Precambrian Time