Question

How was the earths biosphere affected during the Precambrian era

Answer 1

Some three billion years ago, the Earth's atmosphere was virtually devoid of oxygen. At about 2.4 billion years ago, oxygen was released from the seas as a byproduct of photosynthesis by cyanobacteria. Levels of the gas gradually climbed, reaching about one percent around two billion years ago.

Step-by-step explanation:

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