A student investigated the importance of the waxy cuticle on leaves.
The student wiped the cuticle off 20 leaves using a solvent. Another 20 leaves were not wiped.
The student placed the same number of fungal spores on every leaf. After 7 days, the student counted the number of infected leaves.
The Table shows the results.
Table
| Treatment | Number of leaves | Number of infected leaves |
|---|---|---|
| cuticle not removed | 20 | 3 |
| cuticle removed | 20 | 14 |
Calculate the percentage of leaves with the cuticle removed that were infected.
Explain the difference in the results for the two groups of leaves.
Give one variable, other than the number of spores, that the student should control.
Suggest why 3 of the leaves with the cuticle not removed still became infected.
45 exam-style questions on Edexcel GCSE Biology 5.2 Plant and body defences, covering 5.2.1 Physical plant defences, 5.2.2 Chemical plant defences, 5.2.3 Detecting plant diseases, and 5.2.4 Human physical and chemical defences. Each one has a worked solution and a mark scheme showing where the marks go.