Explain convergent evolution with a mammal example.

• A. The process by which two species exchange genes; example: dogs and wolves.
• B. An adaptation that leads to identical genotypes across species.
• C. Independent evolution of similar traits in unrelated lineages due to similar selective pressures; example: aquatic mammals like dolphins and ichthyosaurs.
• D. A gradual build-up of physical size differences within a single population.

Answer: (C)

Convergent evolution happens when different lineages independently evolve similar traits because they face similar environments or selective pressures. In a mammal-focused example, dolphins develop a streamlined, fusiform body, dorsal fin, and tail flukes to move efficiently through water. Those features arise not because they share a recent ancestor with other aquatic animals, but because living in an aquatic lifestyle favors the same functional solution. A classic illustration uses dolphins alongside an extinct marine reptile like the ichthyosaur; although they are not closely related, both show similar adaptations to swimming in the ocean. The important point is that these similarities are analogous—similar function and form arising separately due to similar demands—rather than inherited from a common ancestor. The other ideas describe gene flow, identical genotypes across species, or changes within a single population, which are not about convergence across distinct lineages.