A scientist investigated how tobacco mosaic virus (TMV) spreads between tomato plants.
Each treatment contained 20 healthy plants placed near plants infected with TMV. The insects used in the investigation did not develop disease.
| Treatment | Leaves of healthy and infected plants touching | Insects allowed to move between infected and healthy plants | Number of healthy plants that became infected |
|---|---|---|---|
| 1 | Yes | Yes | 18 |
| 2 | Yes | No | 13 |
| 3 | No | Yes | 11 |
| 4 | No | No | 0 |
Using the results, explain why the insects are described as vectors rather than pathogens.
A grower plans to remove all insects from a glasshouse in which the leaves of neighbouring tomato plants touch. Evaluate whether this would completely prevent TMV spreading between the plants.
252 exam-style questions on AQA GCSE Biology 3.1 Communicable diseases, covering 3.1.1 Communicable (infectious) diseases, 3.1.2 Viral diseases, 3.1.3 Bacterial diseases, 3.1.4 Fungal diseases, 3.1.5 Protist diseases, 3.1.6 Human defence systems, 3.1.7 Vaccination, 3.1.8 Antibiotics and painkillers, and 3.1.9 Discovery and development of drugs. Each one has a worked solution and a mark scheme showing where the marks go.