5.9.1.3 How Oxygen Increased Flashcards by liv s

Q

What did algae and plants do?

A

produce oxygen that is now in the atmosphere by photosynthesis

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Q

When did algae first produce oxygen?

A

2.7 billion years ago
soon after this oxygen appeared

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Q

What happened over the next billion years after oxygen appeared?

A

plants evolved
the percentage of oxygen gradually increased to a level that enabled animals to evolve

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