Biology 9700 · AS & A Level · Variation

Variation — practice question

Sea blush, Pleciritis congesta, is a flowering plant found along the west coast of North America. Individual sea blush plants produce fruit that may be winged or wingless. Investigations have shown that this characteristic is controlled by one gene with two alleles: a dominant allele for winged fruit and a recessive allele for wingless fruit. Fig. 3.1 illustrates the structural contrast between the winged fruit and wingless fruit phenotypes.
(a(i))[1]

A large sample of sea blush fruits was gathered and the fruit-wing characteristic was noted. Name the type of variation shown by the fruit-wing characteristic of sea blush.

(a(ii))[2]

Different sea blush plants may have fruit of different colours. Suggest two ways in which a new fruit colour could arise naturally in a sea blush population.

(a(iii))[3]

At first, taxonomists placed sea blush plants with winged fruits in a different species from sea blush plants with wingless fruits. Since then, observational and experimental evidence has shown that the plants are the same species. Suggest three examples of evidence that helped confirm that these sea blush plants belong to the same species.

(b)[5]

Natural selection happens in populations, for example in sea blush plant populations. Explain why natural selection occurs in populations.

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