A virus causes pale patches on the leaves of courgette plants.
A scientist investigated the role of aphids in spreading the virus. The same number of aphids was used in groups 1 and 2. After the aphids had fed on the donor plants for 24 hours, they were moved to healthy recipient plants. The aphids were removed after a further 24 hours.
Each group contained 20 recipient plants, which were then kept under the same conditions for 14 days.
| Group | Treatment | Number of recipient plants that developed pale patches |
|---|---|---|
| 1 | Aphids fed on diseased donor plants before being moved to healthy recipient plants | 18 |
| 2 | Aphids fed on healthy donor plants before being moved to healthy recipient plants | 0 |
| 3 | No aphids were placed on the healthy recipient plants | 0 |
Explain what the results show about the role of aphids in the spread of the virus.
133 exam-style questions on AQA GCSE Biology 3.3 Plant disease, covering 3.3.1 Detection and identification of plant diseases and 3.3.2 Plant defence responses. Each one has a worked solution and a mark scheme showing where the marks go.