1. The Cambrian Period occurred at the beginning of the

a. Mesozoic Era
b. Paleozoic Era.
c. Phanerozoic Eon.
d two of the above

2. Our own species evolved during the

a. Cambrian Period.
b. Cenozoic Era.
c. Proterozoic Eon.
d. two of the above

3. Which answer best completes the following sentence? "Adaptations help an organism survive .

a. without new mutations.
b. in a specific environment.
c. during a given geologic eon.
d. in any ecosystem on Earth.

4. How did Earth's climate change during the Phanerozoic Eon?

a The climate became steadily colder.
b.The climate became steadily warmer.
c. The climate cycled between warmer and colder.
d. none of the above


5. Which statement about the Cambrian Period is false?

a. It began about 540 million years ago.
b. It had a warm, humid tropical climate.
c. It had an explosion of living things.
d. It ended with the Permian mass extinction.
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