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Questions and Answers
The human body uses around 50% of the oxygen it takes in.
False
Plants need oxygen to survive.
False
High levels of oxygen in the air can be harmful to humans.
True
The Great Oxidation Event occurred around 1 billion years ago.
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Anaerobic life forms need oxygen to survive.
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Fossil evidence suggests that animals first appeared about 500 million years ago.
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Atmospheric oxygen levels have increased steadily over time.
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Insects were able to grow bigger in oxygen-rich atmospheres because they needed larger breathing systems.
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Oxygen levels 240 million years ago were higher than they are now.
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Most of the oxygen in the biosphere is produced on land.
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