One fertilised egg from a species of freshwater fish divided to form eight unspecialised cells. Researchers separated the cells, and each cell developed into a fish. Four fish were reared in tank L and four in tank H. The fish were the same age, and water temperature and light were kept the same.
| Tank | Food supplied per fish per day in g | Mean mass after 12 weeks in g |
|---|---|---|
| L | 0.40 | 18.6 |
| H | 0.70 | 24.2 |
Which conclusion is best supported by the results?
The fish are genetically identical, so the difference in mean mass was most likely caused by the extra food in tank H.
The fish have different genes, because each separated cell received a different part of the embryo's genes.
The fish are genetically identical, so the extra food in tank H probably changed their genes to increase their mass.
The fish have different genes, so the fish given more food may also have had alleles for faster growth.
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.