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Chemistry · Paper 2 · Foundation + Higher · C9

Oxygen increased; carbon dioxide decreased

Key ideas1 of 3

Photosynthesis changes the air

Algae first produced oxygen about 2.7 billion years ago; plants evolved later. Photosynthesis takes in carbon dioxide and releases oxygen:
carbon dioxide + water → glucose + oxygen
Light supplies energy. Rising oxygen eventually allowed animals to evolve.

Photosynthesis uses carbon dioxide and water, with light energy, to form glucose and oxygen.

Next: How the greenhouse effect works →
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Daily 5 · Exam practice · Revision sheet ↓

Foundation + Higher · C9. All C9 lessons are shared by Foundation and Higher Tier.

AQA Combined Science Trilogy 8464 · 5.9.1.3–5.9.1.4. Original notes, questions and diagrams. Models are simplified; illustrative data are labelled.