Labels:book | bulletin board | reckoner OCR: life even had chance to get a root hold or a foothold on land It is not coincidence that the rapid evolution of life from prokaryotes (single-celled organisms with no nucleus to eukarvotes (single celled organisms with a nucleus to metazoa (multicelled organisms) took place in the billion- year- long era of oxygen and ozone Although the atmosphere was reaching a fairly stable level of oxygen during this period, the climate was hardly uniform. There were long stages 01 relative warmth or coolness during the transition to modern geologic time The composition of fossil plankton shells that lived near the ocean floor provides a measure of bottom water temperatures. The record suggests that over the past 100 million years bottom waters cooled by nearly 15 degrees Celsius Sea levels dropped by h ...
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