An ecologist samples four restored wetland pools. The pools have similar temperature, pH, shade and substrate. The ecologist samples the same area for the same length of time in each pool.
| Pool | Bloodworms | Sludgeworms | Freshwater shrimps | Stonefly nymphs |
|---|---|---|---|---|
| J | 0 | 1 | 14 | 12 |
| K | 17 | 15 | 1 | 0 |
| L | 18 | 2 | 10 | 8 |
| M | 2 | 16 | 9 | 7 |
Which pool is most likely to have the lowest dissolved-oxygen concentration?
Pool J
Pool L
Pool M
Pool K
101 exam-style questions on Edexcel GCSE Biology 9.3 Material cycles and decomposition, covering 9.3.1 Cycling of materials through ecosystems, 9.3.2 The carbon cycle, 9.3.3 The water cycle, 9.3.4 The nitrogen cycle, 9.3.5 Indicator species and pollution, 9.3.6 Decomposition in preservation and composting, and 9.3.7 Rate changes in decay of biological material. Each one has a worked solution and a mark scheme showing where the marks go.