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Biological Environment > Air |
This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Note: Many facts have been simplified to make them easier to understand. |
| From 1 billion years ago the atmosphere became richer in oxygen until it reached the high level we find in the air today. This might have been the reason why, around 700 million years ago, amazing things began to happen to protozoa. | ||
| Like this web site? Buy the book! |
Biological Environment > Air |
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