Adult Drosophila fruit flies consume yeasts on the skins of ripe fruit. The females place their eggs within the fruit, and the larvae feed there before becoming adults. The tree Morinda citrifolia bears fruits known as noni fruits. Noni fruits contain a toxin and are rejected by almost all Drosophila species, including Drosophila yakuba in mainland Africa. One population of D. yakuba lives on Mayotte, an island off the African coast. The D. yakuba population on Mayotte has adapted to feed on noni fruit. Flies in this population produce enzymes that make them resistant to the toxin in noni fruits. The adults can feed on yeasts on the fruit surface, and their eggs and larvae can develop and grow inside the fruit. Scientists have used bioinformatics to estimate that the distinctive D. yakuba population on Mayotte arose within the last 30 000 years.
(a)[4]
Describe how a Drosophila population can acquire resistance to noni fruit toxin.
(b)[3]
Explain why living on an island makes it more likely that the noni toxin-resistant D. yakuba population on Mayotte will become a separate species from the mainland D. yakuba population.
(c)[3]
Suggest how scientists might use bioinformatics to estimate how long the D. yakuba population has been living on Mayotte.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A spontaneous / random mutation” …