A student investigates how the starting direction of a root affects its response to gravity.
The student places four similar germinating oat seedlings horizontally in group H. Four other seedlings are placed with their roots pointing vertically downwards in group D. All seedlings are kept in darkness for 48 hours.
The student considers two possible dependent variables:
The results are shown in the table.
| Seedling | Increase in root length in group H (mm) | Angle changed in group H (°) | Increase in root length in group D (mm) | Angle changed in group D (°) |
|---|---|---|---|---|
| 1 | 18 | 36 | 19 | 2 |
| 2 | 20 | 40 | 18 | 0 |
| 3 | 19 | 44 | 20 | 2 |
| 4 | 19 | 40 | 19 | 4 |
Calculate the mean angle through which the roots changed direction for each group.
Evaluate which of the two measurements is more suitable as the dependent variable for this investigation.
105 exam-style questions on Edexcel GCSE Biology 6.3 Plant hormones, covering 6.3.1 Plant hormones and tropisms and 6.3.2 Commercial uses of plant hormones. Each one has a worked solution and a mark scheme showing where the marks go.