Ecologists recorded the presence of a lichen species on 60 stone walls in each of four environmental categories.
| Mean winter temperature / °C | Air pollution | Number of walls where the lichen was present |
|---|---|---|
| 5 | Low | 47 |
| 5 | High | 14 |
| 10 | Low | 49 |
| 10 | High | 43 |
A clean-air programme is expected to change the air pollution from high to low in both temperature regions. The mean winter temperatures are expected to remain unchanged.
Which conclusion about the possible change in the lichen's distribution is best supported?
The larger increase may occur in the 5 °C region, where 47 walls were occupied at low pollution and 14 at high pollution.
The lichen may spread only in the 10 °C region, because that region had more occupied walls at both pollution levels.
The increase may be similar in both regions, because 47 and 49 walls were occupied there at low pollution.
The larger increase may occur in the 10 °C region, because 43 walls were already occupied there under high pollution.
83 exam-style questions on AQA GCSE Biology 7.2 Organisation of an ecosystem, covering 7.2.1 Levels of organisation, 7.2.2 How materials are cycled, 7.2.3 Decomposition, and 7.2.4 Impact of environmental change (HT only). Each one has a worked solution and a mark scheme showing where the marks go.