The table gives the estimated time since the most recent common ancestor of four living species. Assume that each branching point splits one lineage into two.
| Pair | Time / million years |
|---|---|
| P and Q | 3 |
| P and R | 9 |
| Q and R | 9 |
| P and S | 15 |
| Q and S | 15 |
Which missing value and conclusion fit the same tree?
R and S: 9 million years; S separated before the P–Q split.
R and S: 15 million years; S separated before the P–Q split.
R and S: 9 million years; S separated after the P–Q split.
R and S: 15 million years; S separated after the P–Q split.
40 exam-style questions on AQA GCSE Biology 6.4 Classification of living organisms, covering 6.4 Classification of living organisms. Each one has a worked solution and a mark scheme showing where the marks go.