Some students investigated phototropism in the coleoptiles of oat seedlings using two different setups over 48 hours:
The results of the angle of curvature towards the light source (measured in degrees) are shown in the table below:
| Coleoptile number | Setup A (Stationary) curvature (°) | Setup B (Rotating) curvature (°) |
|---|---|---|
| 1 | 41 | 2 |
| 2 | 46 | 1 |
| 3 | 13 | 3 |
| 4 | 38 | 0 |
| 5 | 44 | 2 |
Explain how the rotating board in Setup B acts as a control.
Identify the anomalous coleoptile in Setup A and suggest why including its measurement in the mean calculation reduces the validity of the results.
Calculate a more valid mean angle of curvature for the coleoptiles in Setup A by omitting the anomalous result. Give your answer to 1 decimal place.
59 exam-style questions on AQA GCSE Biology 5.4 Plant hormones, covering 5.4.1 Control and coordination and 5.4.2 Use of plant hormones (HT only). Each one has a worked solution and a mark scheme showing where the marks go.