Scientists rear fish of the same species from two groups, X and Y, that have inherited different alleles. Half of each group is given a low food ration and half is given a high food ration. All other conditions are kept the same.
| Group | Mean body mass after 12 weeks with low food ration / g | Mean body mass after 12 weeks with high food ration / g |
|---|---|---|
| X | 140 | 190 |
| Y | 165 | 215 |
Which conclusion is best supported by these results?
Inherited alleles affected body mass, but food ration did not, because X and Y differed by the same amount on both rations.
Both inherited alleles and food ration affected body mass, because each changed the mean when the other was kept the same.
Food ration affected body mass, but inherited alleles did not, because both groups gained the same mass on the high ration.
The high food ration produced new alleles in the fish, and these new alleles increased their mean body mass.
96 exam-style questions on Edexcel GCSE Biology 3.4 Variation and the Human Genome Project, covering 3.4.1 Causes of variation, 3.4.2 Outcomes of the Human Genome Project, 3.4.3 Genetic variation within a population, and 3.4.4 Effects of genetic mutations on phenotype. Each one has a worked solution and a mark scheme showing where the marks go.