A technician grows matched cultures of microscopic algae in flasks, all under the same light intensity. Half of the cultures are supplied with 0.05% carbon dioxide and the other half with 0.12% carbon dioxide. The cultures are kept at a range of temperatures, and the rate of photosynthesis of each culture is measured.
| Temperature (∘C^\circ\text{C}∘C) | 10 | 15 | 20 | 25 | 30 |
|---|---|---|---|---|---|
| Rate of photosynthesis at 0.05% carbon dioxide in arbitrary units | 4 | 9 | 15 | 20 | 20 |
| Rate of photosynthesis at 0.12% carbon dioxide in arbitrary units | 4 | 9 | 15 | 25 | 32 |
Which statement correctly identifies the factor limiting the rate of photosynthesis at 15 ∘C15\ ^\circ\text{C}15 ∘C and 0.12% carbon dioxide?
No factor, because the rate is the same at both carbon dioxide concentrations at this temperature.
Temperature, because raising the carbon dioxide concentration at 15 ∘C15\ ^\circ\text{C}15 ∘C does not change the rate.
Carbon dioxide concentration, because the higher concentration gives a faster rate at 30 ∘C30\ ^\circ\text{C}30 ∘C.
Light intensity, because it is the only condition that is kept the same for every culture.
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.