A plant nursery investigated whether removing tomato plants showing mosaic leaf discolouration reduced the spread of tobacco mosaic virus (TMV).
Tomato plants were placed in two sets of growing areas. The starting density of plants and all other conditions were the same.
In group N, no plants were removed. In group R, any plant showing mosaic leaf discolouration was removed each day.
The results after six weeks are shown in the table.
| Group | Number of healthy plants at the start | Number of these plants that developed mosaic leaf discolouration |
|---|---|---|
| N | 80 | 32 |
| R | 120 | 24 |
State the dependent variable in this investigation.
Calculate the percentage reduction in the proportion of initially healthy plants that developed mosaic leaf discolouration when infected plants were removed.
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.