CAIE A Level Biology 9700 · Selection and evolution
In the alpine plant Gentiana verna, the number of petals per flower is either 4 or 5; there are no intermediate numbers. In the garden rose Rosa × hybrida, the number of petals per flower varies continuously from 6 to 12.
Compare the genetic basis of discontinuous variation in G. verna with that of continuous variation in R. × hybrida.
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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