CAIE A Level Biology 9700 · Selection and evolution
A population of birds on a mainland has a wide range of beak lengths. A small flock of 20 birds colonises a distant island. The allele frequencies for beak length in the island population are different from those in the mainland population. Explain how the founder effect has caused this difference and how it may affect the future evolution of the island population.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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