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9.1 The composition and evolution of the Earth's atmosphere

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Question 11
F

After algae first appeared, the percentage of oxygen in the atmosphere increased only gradually over about one billion years. Which statement explains why the increase was gradual?

[1]
A

Algae could only photosynthesise in daylight, so oxygen was made slowly

B

Oxygen dissolved in the oceans as fast as the algae could produce it

C

Animals evolved at the same time and respired most of the oxygen away

D

Plants evolved slowly, so the total rate of photosynthesis rose slowly

Markscheme

9.1 The composition and evolution of the Earth's atmosphere Questions

  1. GCSE
  2. /Chemistry
  3. /9.1 The composition and evolution of the Earth's atmosphere

40 exam-style questions on AQA GCSE Chemistry 9.1 The composition and evolution of the Earth's atmosphere, covering 9.1.1 The proportions of different gases in the atmosphere, 9.1.2 The Earth's early atmosphere, 9.1.3 How oxygen increased, and 9.1.4 How carbon dioxide decreased. Each one has a worked solution and a mark scheme showing where the marks go.

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