Scientists investigate two groups of freshwater fish, P and Q, collected from separate spring pools.
They breed fish in three types of pairing. The first-generation offspring are raised to adulthood. For each type of original pairing, the scientists place ten pairs of adult first-generation offspring in the same suitable breeding conditions and record whether each pair produces offspring.
| Pairing of original adult fish | Mean number of first-generation offspring produced per original pair | Pairs of adult first-generation offspring that produced offspring, out of 10 |
|---|---|---|
| P × P | 31 | 9 |
| Q × Q | 29 | 10 |
| P × Q | 26 | 0 |
Explain whether groups P and Q should be classified as the same species. Use all the results in the table.
DNA sequencing shows that groups P and Q have very similar base sequences. Explain whether this evidence should change the conclusion in part (a).
122 exam-style questions on OCR GCSE Biology 5.2 Natural selection and evolution, covering 5.2.1 Genetic variation within a population, 5.2.2 Developments in classification systems, 5.2.3 How evolution occurs through natural selection, 5.2.4 Evolution as change over time, 5.2.5 Evidence for evolution, and 5.2.6 Darwin and Wallace. Each one has a worked solution and a mark scheme showing where the marks go.