Practice mode Evolution

Which group of organisms is credited with adding most of the free oxygen to Earth’s early atmosphere?

Correct answer B. Cyanobacteria

Explanation

Cyanobacteria carried out oxygen-releasing photosynthesis, splitting water. Over long periods their O₂ accumulated in the atmosphere, changing it from reducing to oxidising.

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Which group of organisms is credited with adding most of the free oxygen to Earth’s early atmosphere?

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Which group of organisms is credited with adding most of the free oxygen to Earth’s early atmosphere?

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