Final answer:
Charles Darwin's observations on the Galápagos Islands included the unique adaptations of the Galápagos tortoises, distinct species of iguanas, and the beak variations of finches, all of which supported his foundation for the theory of evolution by natural selection.
Step-by-step explanation:
Charles Darwin's Observations on the Galápagos Islands
During his voyage on the HMS Beagle, Charles Darwin made crucial observations on the Galápagos Islands that heavily contributed to the development of his theory of evolution by natural selection. One of his most notable observations was that similar species differed from one island to another. Darwin saw that the Galápagos tortoises had various shell shapes adapted to their environments, and that finches had different beak shapes correlating to their specific dietary needs, which varied from island to island.
In particular, he observed two distinct species of iguanas, one aquatic that fed on seaweed and another terrestrial that ate cactus. Moreover, Darwin's research revealed that tortoises could be identified by their shell shapes, indicative of the island they inhabited, which tied to their eating habits and environmental factors. His insight into the specialized characteristics of the Galápagos finches, such as the beak variations that suited different food sources, added substantial evidence to his hypotheses about adaptations and the survival of species.