The table shows observations from a lake after fertiliser enters it.
Table
| Time | Algal abundance | Dead organic material | Dissolved oxygen |
|---|---|---|---|
| Start | low | low | high |
| Later | high | low | high |
| Final | falling | high | low |
Which explanation best accounts for the final oxygen concentration?
Respiration by decomposers increases as more dead material becomes available.
Photosynthesis by decomposers decreases as more dead material becomes available.
Respiration by decomposers decreases as more dead material becomes available.
Photosynthesis by decomposers increases as more dead material becomes available.
38 exam-style questions on Edexcel GCSE Biology 9.2 Energy transfer and biodiversity, covering 9.2.1 Energy transfer between trophic levels, 9.2.2 Efficiency of energy transfers, 9.2.3 Human interactions and biodiversity, 9.2.4 Benefits of maintaining biodiversity, and 9.2.5 Biological factors affecting food security. Each one has a worked solution and a mark scheme showing where the marks go.