Multiple choice

During which geological period did the earth become oxygen rich?

  1. Orosirian period

  2. Ediacaran period

  3. Devonian period

  4. Ordovician period
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A Correct answer
Explanation

The Great Oxygenation Event occurred during the Paleoproterozoic era, specifically the Orosirian period (approximately 2.4-2.0 billion years ago). Cyanobacteria began producing oxygen through photosynthesis, dramatically changing Earth's atmosphere. The Ediacaran period saw the first complex multicellular life. The Devonian is known as the Age of Fish. The Ordovician saw early marine diversification but occurred after oxygen levels were already established.

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