Similarly, in 1859, Charles Darwin recognized that millions of years were necessary for small evolutionary changes to accumulate and produce the variety of life we see today. ... Precambrian rocks are mostly covered by rock systems of more recent origin. ... At the later end of the Paleozoic, the first and the largest mass extinction in history wiped out approximately 90% of all marine animal species. ...

• Word Count: 1841
• Approx Pages: 7
• Grade Level: Undergraduate