Question

marsupials are mammals found only in isolated regions of australia and new guinea. scientists believe this is due to australia’s position in pangaea, as seen in the diagram above. marsupials evolved differently from mammals on other continents. what is the best explanation for how marsupials evolved? select one: a. homologous structures b. biogeographic isolation c. vestigial structures d. molecular similarities

Explanation:

Biogeographic isolation occurs when a population of organisms is separated by a geographic barrier (like continental drift splitting Pangaea, isolating Australia). This separation prevents gene flow with other populations, allowing the isolated group (marsupials) to evolve independently to adapt to their unique environment, which matches the scenario described. Homologous structures refer to similar body parts from common ancestors, vestigial structures are leftover, non-functional body parts, and molecular similarities relate to shared genetic sequences—none of these explain the geographic-based divergent evolution of marsupials.

Answer:

b. Biogeographic isolation