Table 1 shows how photosynthetic life and the composition of Earth's atmosphere have changed over geological time.
| Geological Period | Photosynthetic/Plant Life | Carbon Dioxide (CO2CO_2CO2) in Atmosphere | Oxygen (O2O_2O2) in Atmosphere |
|---|---|---|---|
| 4.5 billion years ago | None | Extremely high (>90%) | 0% |
| 2.5 billion years ago | First photosynthetic algae evolved | High | Trace amounts (<1%) |
| 300 million years ago | Vast, dense global forests | Very low (approx. 0.03%) | High (approx. 21%) |
| Modern era | Reduced 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:
Practise Edexcel GCSE Chemistry Earth and atmospheric science with exam-style questions for Foundation and Higher tier. 62 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
