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GCSE Combined Science · key term
Organisms that can photosynthesise, many of which live in water. Early algae produced oxygen that began to accumulate in the atmosphere.
Used by AQA
Specification 5.9.1.3 · Paper 4
Revise: Increase of Atmospheric OxygenThe oxygen now present in the atmosphere was produced by algae and plants through photosynthesis. Before oxygen began to accumulate, Earth's early atmosphere contained little or no oxygen gas. The appearance of photosynthesising organisms therefore changed the conditions in which other life could evolve.
For an explanation of increasing oxygen, link algae and plants to photosynthesis, then state that photosynthesis releases oxygen.
Remember the sequence: algae produced oxygen about 2.7 billion years ago; plants evolved over the next billion years; oxygen gradually increased, enabling animals to evolve.
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