Final answer:
Charles Darwin specialized in studying barnacles, and his important observations of finches in the Galápagos Islands greatly contributed to his development of the theory of evolution by natural selection.
Step-by-step explanation:
Charles Darwin, who is renowned for proposing the theory of evolution by natural selection, specialized in the study of barnacles rather than being a marine biologist with a focus on whales, fishes, marine birds, or oysters. While Darwin is most famous for his work on evolution, during his voyage on the HMS Beagle, he closely studied a variety of species including birds, particularly the Galápagos finches. These observations in the Galápagos Islands played a pivotal role in the development of his evolutionary theory. Darwin noticed that even though finches from different islands had evolved different beak structures to adapt to their specific dietary needs, they all shared common ancestry. It was through these insights that he began to formulate the concept of natural selection, which suggests that beneficial traits become more common in a species over time because they improve the chances of survival and reproduction.