A student placed a small fern in a transparent chamber. The student tested four light intensities in increasing order, using the same fern without replacing the air between tests. The temperature was kept constant.
| Relative light intensity / arbitrary units | Carbon dioxide concentration at the start of the test / % | Oxygen volume produced in 20 min / cm³ |
|---|---|---|
| 100 | 0.040 | 1.0 |
| 200 | 0.035 | 2.0 |
| 400 | 0.025 | 2.0 |
| 800 | 0.015 | 2.0 |
The student concluded that light intensity was no longer a limiting factor above 200 arbitrary units.
Evaluate the student's conclusion and suggest one change to the method that would allow this conclusion to be tested more reliably.
87 exam-style questions on Edexcel GCSE Biology 6.1 Photosynthesis, covering 6.1.1 Photosynthetic organisms as producers, 6.1.2a Limiting factors on the rate of photosynthesis, 6.1.2b Interactions of limiting factors on photosynthesis, and 6.1.3 Inverse square law and light intensity. Each one has a worked solution and a mark scheme showing where the marks go.