Final answer:
Charles Darwin developed the theory of evolution by natural selection based on his discoveries as a naturalist aboard the HMS Beagle, which toured the coasts of South America and visited the Galapagos Islands. His theory suggests that animals are well-suited for their specific environments.
Step-by-step explanation:
Charles Darwin developed the theory of evolution by natural selection. His observations on the Galápagos Islands suggested that animals are well-suited for their specific environments. Darwin's arguments were based on his discoveries as a naturalist aboard the HMS Beagle, which toured the coasts of South America and visited the Galapagos Islands. He concluded that changes over time within species could account for his observations.