Cambrian Explosion

 

 

Between 570 and 530 million years ago, a surge of different organisms occurred that is now called the “Cambrian explosion.” The best fossil record of this event is the Burgess Shale in British Columbia. Brachiopods, trilobites, mollusks, and other organisms first appeared in the fossil record in the middle of the Cambrian period, when the Cambrian explosion had been underway. Scientists speculate that the increase in oxygen levels may have been the reason behind the sudden appearance of diverse organisms.

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Photoographer: Kevinzim, Nov 5, 2004, http://www.everystockphoto.com/photo.php?imageId=1034596&searchId=bd2ad056056683306b5730e3f2e8ff13&npos=11

Source:

http://www.pbs.org/wgbh/evolution/library/03/4/l_034_02.html

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