Scientists investigated body mass in two breeding lines of the same species of fish. From the same age, equal numbers from each line were given either 1.5 g or 2.5 g of food per day. All other conditions were kept the same. The mean body mass of each group was calculated after 10 weeks.
The results are shown in the table.
| Breeding line | Mean body mass with 1.5 g of food per day (g) | Mean body mass with 2.5 g of food per day (g) |
|---|---|---|
| R | 42 | 57 |
| S | 50 | 67 |
Explain what the results suggest about the causes of variation in 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.