Ecologists surveyed lichens in the same 25 marked sections of a stone wall in Year 1 and Year 6.
The relative abundance is the percentage of all lichen records belonging to each species.
| Lichen species | Tolerance of air pollution | Relative abundance in Year 1 (%) | Relative abundance in Year 6 (%) |
|---|---|---|---|
| A | low (sensitive) | 6 | 31 |
| B | medium | 24 | 44 |
| C | high (tolerant) | 70 | 25 |
It is claimed that the air quality near the wall improved between Year 1 and Year 6.
Evaluate the claim that the air quality improved. Use the information in the table.
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.