This Least Understood Eon of Earth's History Has Not Been

Q8: One hypothesis for the extinction that took

Q17: The cells of these primitive organisms lack

Q18: The_ means "the sun in the making."<br>A)presun<br>B)sol<br>C)protosun<br>D)solar

Q19: By the close of the Paleozoic, all

Q20: The_ period is sometimes called the "golden

Q21: The_ era is known as the "age

Q23: Mammals became the dominant land animals during

Q24: The Precambrian rock record indicates that much

Q26: The age of Earth is about _.<br>A)195

Q27: Which one of the following represents the