Drosophila, the fruitfly, includes many species. Three of them, Drosophila pseudoobscura, D. persimilis and D. miranda, are believed to be closely related. Samples of these three species were gathered from the western United States of America. Fig. 5.1 shows the places where these species naturally occur.
(a)[2]
With reference to Table 5.1, describe the evidence that D. miranda may be more closely related to D. persimilis than to D. pseudoobscura.
(b)[2]
Suggest why divergence is greater in some regions of DNA than in others.
(c)[4]
The region in which D. pseudoobscura is found is separated from the regions where the other two species are found by a high range of mountains. Explain how the species D. pseudoobscura could have evolved from a population of D. miranda.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Divergence values are lower for $persimilis$ than for $pseudoobscura$” …