Biology 9700 · AS & A Level · Evolution

Evolution — practice question

Bison are a kind of large wild cattle. Ancestors of modern bison first appeared in Asia 2.5 million years ago. This ancestral bison species expanded into Europe and North America. Although the ancestral species is now extinct, its descendants are Bison bonasus, the European bison, and Bison bison, the American bison. Fig. 5.1 depicts an American bison.
(a)[4]

When the last ice age ended, ancestral bison populations were split by sea and by forests that were unsuitable habitats. This separation gave rise to the European bison and the American bison. Explain how this separation led to the evolution of the two bison species.

(b)[3]

Table 5.1 compares characteristics of European bison and American bison. Assess the relative importance of natural selection and genetic drift in producing the different heights and masses of the two species of bison.

(c)[3]

The European bison has a nuclear genome that is very similar to that of the American bison. The European bison has a mitochondrial genome that is more similar to that of wild cattle of the genus Bos than to the American bison. Discuss what this suggests about the evolutionary history of the European bison.

(d)[4]

Outline how practical techniques could be used to test the hypothesis that farmed cattle are closely related to European bison.

Worked solution & mark scheme

This 14-mark question has a full step-by-step worked solution and mark scheme. One marking point: geographic isolation

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