Ecologists compared the water in two flooded quarry pits. The pits had similar depth, shade, temperature and pH.
The ecologists used the same sampling effort at each pit but sampled on only one occasion.
| Measurement | East pit | West pit |
|---|---|---|
| Mean number of freshwater shrimps | 18 | 3 |
| Mean number of stonefly nymphs | 12 | 0 |
| Mean number of bloodworms | 1 | 15 |
| Mean number of sludgeworms | 0 | 11 |
| Dissolved oxygen concentration in mg dm⁻³ | 8.7 | 3.2 |
Evaluate the conclusion that the East pit contains cleaner, better-oxygenated water than the West pit.
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.