A pair of freshwater fish produced 120 offspring by sexual reproduction. At hatching, the offspring were divided randomly into two equal groups.
Each fish was kept separately. The temperature, light conditions and volume of water were the same for every fish. The groups received different amounts of food each day.
The body mass of each fish was measured at 16 weeks.
| Daily food ration per fish (mg) | Mean body mass at 16 weeks (g) | Range of body masses at 16 weeks (g) |
|---|---|---|
| 15 | 1.8 | 1.3–2.4 |
| 30 | 2.7 | 2.0–3.5 |
Explain why the offspring did not all have the same body mass, using the information in the table.
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.