A microscopic alga has two inherited cell types: salt-tolerant and not salt-tolerant. The cells reproduce asexually, so daughter cells inherit the cell type of the cell that produced them.
The table shows what happens as sample P is used to produce sample Q.
| Stage | Salt-tolerant cells | Cells that are not salt-tolerant |
|---|---|---|
| Number of cells in sample P | 160 | 640 |
| Proportion remaining alive after exposure to increased salinity | 3 out of 4 | 1 out of 4 |
| Daughter cells formed by each remaining cell | 4 | 2 |
Sample Q contains only the daughter cells. No mutations occur and no other cells enter either sample.
Which option gives the percentage of salt-tolerant cells in sample P and in sample Q?
Sample P: 80.0%; sample Q: 40.0%.
Sample P: 20.0%; sample Q: 42.9%.
Sample P: 20.0%; sample Q: 60.0%.
Sample P: 20.0%; sample Q: 75.0%.
80 exam-style questions on AQA GCSE Biology 6.2 Variation and evolution, covering 6.2.1 Variation, 6.2.2 Evolution, 6.2.3 Selective breeding, 6.2.4 Genetic engineering, and 6.2.5 Cloning. Each one has a worked solution and a mark scheme showing where the marks go.