CAIE A Level Biology 9700 · Selection and evolution
In a species of sunflower, the number of ray florets on the flower head shows discontinuous variation: individuals have either 8 or 13 florets, with no intermediate numbers. The seed mass, however, shows continuous variation from 2 mg to 8 mg. Compare discontinuous and continuous variation with reference to their genetic basis, the influence of environmental factors, and the suitability of using a t-test to compare two populations for each trait.
7 marks, so the mark scheme is looking for about 7 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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