CAIE A Level Biology 9700 · Selection and evolution
The table shows the percentage similarity of a 500-base-pair region of mitochondrial DNA from three species of birds (A, B, C) from different islands.
| Species pair | DNA sequence similarity (%) |
|---|---|
| A and B | 98.0 |
| A and C | 92.5 |
| B and C | 93.0 |
Outline how data of this type can be used to infer evolutionary relationships between species. Also outline the processes of allopatric and sympatric speciation that could lead to the formation of new species from a common ancestor.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Outline means: Give the main points briefly. Less detail than describe, but every key step has to be there. One short line per step, in order. The marks are for coverage, not depth.
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