Dog and bat forelimbs each contain one upper bone, two lower bones, wrist bones and five digits. Fossil and genetic evidence indicates that both species inherited this limb plan from a common ancestor. The corresponding bones now differ in their relative lengths and shapes; dogs use their forelimbs for running and bats use theirs for flying.
Which conclusion is best supported?
Repeated use altered each animal's limb bones and the acquired changes were inherited.
Different bone proportions show that the forelimbs are no longer homologous structures.
The need for each movement caused mutations that produced suitable bone proportions.
Different selection pressures modified the ancestral limb plan for running and flying.
85 exam-style questions on Edexcel GCSE Biology 4.1 Evolution and natural selection, covering 4.1.1 Work of Darwin and Wallace and 4.1.2 Resistant organisms and evolution. Each one has a worked solution and a mark scheme showing where the marks go.