AQA · Chemistry · 8462
GCSE Chemistry: How oxygen increased
Chemistry of the atmosphere · AQA GCSE Chemistry (8462), specification point 4.9.1.3. Cards are generated from the exam board's own specification for "How oxygen increased", and every card links back to the page it came from. Specification © AQA — used with attribution.
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Which organisms produced the oxygen now in the atmosphere?
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Algae and plants, by photosynthesis.
Which process produced the oxygen in Earth's atmosphere?
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Photosynthesis, carried out by algae and later plants.
What is the word equation for photosynthesis?
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Carbon dioxide + water → glucose + oxygen (using light energy).
What is the balanced symbol equation for photosynthesis?
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6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Approximately how many years ago did algae first produce oxygen?
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About 2.7 billion years ago.
Algae first produced oxygen about ? billion years ago.
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2.7
Which organisms were the first to produce oxygen on Earth?
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Algae — plants evolved later, over the following billion years.
Roughly how long after algae appeared did plants evolve and raise oxygen levels?
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Over the next billion years.
Why did rising atmospheric oxygen levels matter for animals?
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Oxygen gradually reached a level high enough to enable animals to evolve.
How could you show experimentally that aquatic plants produce oxygen?
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Leave aquatic plants (e.g. pondweed) in daylight and collect the gas given off; it relights a glowing splint.
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