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Changes in the trilobite exoskeleton can be attributed to ____. |
d. both a and b |
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Changes in the environment result in ____. |
physical changes in species |
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____ on the geologic time scale are marked by major, striking, and worldwide changes in the type of fossils present. |
Eras |
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____ is a process by which organisms with characteristics suited to the environment will survive and reproduce. |
Natural selection |
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Scientists used major changes in life forms in the fossil record to form the geologic time scale. |
T |
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If a species can adapt to a changing environment, or ____, its descendants will survive. |
evolve |
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Dog breeding is an example of natural selection. |
F |
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Geologic time is divided into units based upon types of ____. |
organisms |
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The division of Earth’s history into smaller units makes up the ____. |
geologic time scale |
|
Trilobites are index fossils because they ____. |
all of the above |
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