An ecologist samples a small plant species on a sand dune.
Four transects are placed from the seaward edge of the dune towards the inland side. A 0.25 m² quadrat is placed at each stated distance along every transect.
The table shows the number of plants counted in each quadrat.
| Distance from seaward edge in m | Transect 1 | Transect 2 | Transect 3 | Transect 4 |
|---|---|---|---|---|
| 0 | 0 | 0 | 1 | 0 |
| 10 | 2 | 3 | 2 | 3 |
| 20 | 6 | 7 | 8 | 7 |
| 30 | 4 | 15 | 6 | 14 |
| 40 | 9 | 10 | 11 | 10 |
The ecologist can collect more results at only one distance.
Suggest the distance at which the ecologist should use more quadrats.
Calculate the difference between the highest and lowest counts at this distance and compare this difference with the results at the other distances.
Explain how the ecologist should collect and use the additional results to make the investigation more reliable.
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.