At a plant research station, water containing nitrate fertiliser leaked from plant-growing tanks into an enclosed outdoor pond. After an algal bloom, scientists collected the following data.
| Day after the algal bloom reached its maximum size | Mass of dead algal material in the water in mg dm⁻³ | Dissolved oxygen in mg dm⁻³ | Number of live fish in the pond |
|---|---|---|---|
| 1 | 3.0 | 8.4 | 64 |
| 8 | 21.0 | 2.0 | 26 |
Scientists suggest removing most of the dead algal material from the pond.
Using the data, explain why this could reduce further fish deaths.
100 exam-style questions on Edexcel GCSE Biology 4.3 Selective breeding and genetic modification, covering 4.3.1 Selective breeding and its impact, 4.3.2 Tissue culture, 4.3.3 Genetic engineering overview, 4.3.4 Main stages of genetic engineering, 4.3.5 Advantages and disadvantages of GM organisms, 4.3.6 Agricultural solutions for a growing population, and 4.3.7 Evaluating genetic engineering and breeding. Each one has a worked solution and a mark scheme showing where the marks go.