Three populations of freshwater fish, R, S and T, have been isolated in separate lakes for many generations. A researcher crosses healthy adults from different populations under suitable breeding conditions. Each cross produces offspring.
The results are shown in the table.
| Populations crossed | Offspring surviving to adulthood | Offspring that later produced young |
|---|---|---|
| R and S | 18 | 15 |
| R and T | 17 | 0 |
| S and T | 16 | 0 |
Which conclusion is best supported by the results?
R and T are one species but S is a different species, because more R and T offspring survived than S and T offspring.
R and S are one species but T is a different species, because only the R and S cross gave fertile offspring.
All three populations are one species, because every cross gave offspring that survived to adulthood.
All three populations are different species, because some offspring from every cross did not produce young.
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.