Biology 9700 · AS & A Level · Natural and artificial selection
Natural and artificial selection — practice question
From 1975 to 1977, one of the Galapagos Islands, Daphne Major, went through a drought. On Daphne Major, the ground finch, Geospiza fortis, feeds on seeds. One of the few plants that survived the drought produced large seeds inside hard fruits. Many G. fortis died during the drought, so the population fell from 1400 in 1975 to 190 in 1977. The mean beak depth of the G. fortis that died was 10.68 mm, while the mean beak depth of those that survived was 11.07 mm. Before the drought, the mean beak depth of G. fortis was 10.86 mm.
(a)[2]
Calculate the percentage fall in population size between 1975 and 1977. Include every stage in your calculation and give the answer to the nearest whole number.
(b)[3]
Suggest why some G. fortis managed to survive the drought whereas others died.
(c)[2]
Natural selection was occurring on Daphne Major. State the type of natural selection that operated on G. fortis during the drought and explain your answer.
Worked solution & mark scheme
This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: “86” …