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9.2 Earth and atmospheric science

9.2 Earth and atmospheric science

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Question 15

Table 1 shows how photosynthetic life and the composition of Earth's atmosphere have changed over geological time.

Geological PeriodPhotosynthetic/Plant LifeCarbon Dioxide (CO2CO_2CO2​) in AtmosphereOxygen (O2O_2O2​) in Atmosphere
4.5 billion years agoNoneExtremely high (>90%)0%
2.5 billion years agoFirst photosynthetic algae evolvedHighTrace amounts (<1%)
300 million years agoVast, dense global forestsVery low (approx. 0.03%)High (approx. 21%)
Modern eraReduced forest cover (deforestation)Increasing (approx. 0.04%)Stable (approx. 21%)

Explain the effects that photosynthetic life has had on the composition of the Earth's atmosphere and on global temperature.

In your answer, refer to the data in Table 1 and include:

  • the role of photosynthesis
  • the changes in the levels of carbon dioxide and oxygen
  • how these changes affected global temperature
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Markscheme

9.2 Earth and atmospheric science Questions

  1. GCSE
  2. /Chemistry
  3. /9.2 Earth and atmospheric science

97 exam-style questions on Edexcel GCSE Chemistry 9.2 Earth and atmospheric science, covering 9.2.1 The Earth's early atmosphere, 9.2.2 How the atmosphere evolved, 9.2.3 Chemical test for oxygen, and 9.2.4 The greenhouse effect and climate change. Each one has a worked solution and a mark scheme showing where the marks go.

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