Question

Sophie says dolphins and sharks look very similar, so they must be related. Jake disagrees, saying DNA evidence has shown that dolphins and other aquatic mammals are actually more closely related to the ancestors of modern hippos. Who is correct using the modern system of classification?
Sophie is correct because dolphins look more like sharks than like hippos.
Jake is correct because classification is based on evolutionary relationships.
Both are correct because traditional and modern classifications can overlap.
Neither is correct because neither is taking into account both the traditional and modern systems

Answer 1

Jake is correct because modern (phylogenetic) classification is based on evolutionary relationships. Dolphins are mammals (Cetacea) and molecular evidence places them closest to artiodactyls like hippos; sharks are cartilaginous fishes (very distant). The dolphin–shark resemblance is convergent evolution (similar body shapes adapted to swimming), not close common ancestry.