CAIE A Level Biology 9700 · Selection and evolution
In a plant species, leaf length varies continuously from 5 cm to 20 cm, while flower petal number shows only two distinct values: 4 or 5, with no intermediates. Compare the genetic basis of continuous variation (leaf length) with that of discontinuous variation (petal number).
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.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
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