An ecologist grows young plants for habitat restoration.
The ecologist uses the increase in dry mass over seven days to compare the rates of photosynthesis under four conditions. All the plants are the same species and start with the same mean dry mass. The temperature is kept at 25 ∘C25\ ^\circ\text{C}25 ∘C.
The plants are currently grown under condition P. The ecologist can first increase either the light intensity, producing condition Q, or the carbon dioxide concentration, producing condition R.
| Condition | Light intensity in arbitrary units | Carbon dioxide concentration in % | Mean increase in dry mass in mg day−1\text{mg day}^{-1}mg day−1 |
|---|---|---|---|
| P | 40 | 0.04 | 6 |
| Q | 80 | 0.04 | 6 |
| R | 40 | 0.10 | 8 |
| S | 80 | 0.10 | 12 |
Explain which factor the ecologist should increase first to raise the rate of photosynthesis.
After making this first change, predict which factor the ecologist should increase next to raise the rate of photosynthesis further. Justify your answer using the data.
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.