Earth Formed Approximately______ Years Ago

Q13: Most _rocks are devoid of fossils; consequently

Q14: Following the reptilian extinctions at the close

Q15: The first fully land- based animals were_.<br>A)

Q16: During the Cambrian, Trilobites developed a flexible

Q17: The heaviest element produced by nuclear fusion

Q19: Examine the words and/or phrases below and

Q20: Sea level is constant over long periods

Q21: Primitive organisms, called _ nuclei.<br>A) stromatolites<br>B) eukaryotes<br>C)

Q22: Earth's most important internal heat source is/are_

Q23: A major economic deposit associated with the