At least half of the oxygen in Earth's atmosphere was created by

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Quizplus · Accepted Answer

Phytoplankton in the ocean are responsible for at least half of the oxygen in Earth's atmosphere through the process of photosynthesis. They use sunlight to convert carbon dioxide and water into organic matter and oxygen. Trees in the boreal forest also contribute to oxygen production, but to a lesser extent. Burning fossil fuels actually decreases the amount of oxygen in the atmosphere by releasing carbon dioxide, which is not converted back to oxygen through natural processes. Plants, algae, and phytoplankton in the intertidal zone also contribute to oxygen production, but not on the same scale as phytoplankton in the ocean.

At Least Half of the Oxygen in Earth's Atmosphere Was