A scientist puts equal concentrations of the same microscopic alga into three sealed tubes of water. Each tube is kept at the same temperature and exposed to light of the same intensity for 30 minutes. A sensor measures the concentration of a dissolved gas, Y.
| Colour of light | Concentration of gas Y at the start (mg dm−3\text{mg dm}^{-3}mg dm−3) | Concentration of gas Y after 30 minutes (mg dm−3\text{mg dm}^{-3}mg dm−3) |
|---|---|---|
| red | 6.0 | 8.8 |
| green | 6.0 | 6.6 |
| blue | 6.0 | 9.1 |
Explain the results, including the identity of gas Y.
117 exam-style questions on OCR GCSE Biology 1.4 Photosynthesis, covering 1.4.1 Photosynthesisers as biomass producers, 1.4.2 Factors affecting the rate of photosynthesis, and 1.4.3 Limiting factors in photosynthesis. Each one has a worked solution and a mark scheme showing where the marks go.