Scientists used a computer model to investigate changes after algae first appeared.
The table shows outputs from the model.
| Time after algae first appeared in billions of years | Available habitat occupied by algae and plants in % | Oxygen in the atmosphere in % |
|---|---|---|
| 0.00 | 0.1 | 0.01 |
| 0.25 | 2.0 | 0.08 |
| 0.50 | 10 | 0.40 |
| 0.75 | 30 | 1.5 |
| 1.00 | 65 | 5.0 |
Using the data and your knowledge of photosynthesis, explain the pattern in atmospheric oxygen during the one-billion-year period. Explain how the change in oxygen affected the evolution of animal life.
79 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.