Concept
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Created by Boundless
The Cambrian Explosion of Animal Life
Earth's oxygen concentration
The oxygen concentration in earth's atmosphere rose sharply around 300 million years ago.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"OpenStax College, Biology. November 14, 2013."
http://cnx.org/content/m44660/latest/?collection=col11448/latest
OpenStax CNX
CC BY 3.0.