Biology 9700 · AS & A Level · Natural and artificial selection
Natural and artificial selection — practice question
Drug therapy is the chief way malaria cases are treated. Several different drugs have been used to destroy a species of the Plasmodium parasite that causes malaria. For many years, chloroquine was the main drug used in Africa. In 1996, the newer drug sulfadoxine-pyrimethamine (Fansidar), replaced it and chloroquine use was stopped. A study was done to estimate the percentage of parasites killed by the two different drugs in two African countries. The findings of the study are shown in Table 4.1.
(a)[3]
With reference to Table 4.1, describe how the effectiveness of the two drugs differs.
(b)[2]
Explain how the data in Table 4.1 provide evidence that chloroquine use was stopped after 1996.
(c)[4]
The researchers concluded that, in both Kenya and Uganda, the parasite had evolved resistance to sulfadoxine-pyrimethamine. Explain how the parasites evolved resistance.
(d)[1]
Chloroquine resistance in Plasmodium was traced to a difference in the shape of one particular cell surface membrane protein. Name the type of variation that controls chloroquine resistance in the Plasmodium population.
(e)[2]
Plasmodium has a very complex life cycle with several stages. The stages that infect humans are haploid. Suggest why the Hardy-Weinberg principle cannot be applied to calculate the frequency of the allele for chloroquine resistance.
Worked solution & mark scheme
This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Fansidar® shows greater effectiveness than chloroquine in most situations” …