CAIE A Level Biology 9700 · Selection and evolution
A population of a single bird species lives on an isolated island. Over time, two distinct groups emerge that do not interbreed. One group has a different mating song and feeds on a different type of seed than the other group. Both groups occupy the same geographical area. Describe how this behavioural isolation can lead to sympatric speciation. Explain how comparing DNA sequences from the two groups could provide evidence for their evolutionary relationship.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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