Evidence of Evolution Practice Test

Researchers sequence a 900-base-pair region of a mitochondrial gene from three island bird populations (X, Y, Z) and a mainland population (M). They find that X and Y differ by 6 bases, X and Z differ by 42 bases, and Y and Z differ by 45 bases. Each island population is geographically isolated, and all populations have similar diets and body sizes. Which conclusion is best supported by the molecular differences among these populations?

A paleontologist compares limb bones in four vertebrate lineages. Fossils of early tetrapods (about 360 million years old) show a forelimb with one proximal bone, two distal bones, several wrist bones, and digits. Modern frogs, lizards, bats, and whales also have forelimbs with the same bone arrangement, although the bones differ in relative size and function (jumping, running, flying, swimming). No evidence suggests these lineages acquired the limb pattern through interbreeding. Which conclusion is best supported by the shared forelimb bone pattern across these lineages?