CAIE A Level Biology 9700 · Selection and evolution
A species of lizard, Anolis carolinensis, is found on the mainland of a continent. A small number of individuals are swept out to sea on a floating log and eventually reach a distant island, where they establish a new population. After many generations, the island lizards are unable to produce fertile offspring when crossed with mainland lizards. Explain how changes to the gene pool over generations could have led to the formation of a new species on the island.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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