What adaptations did Darwin observe in the organisms found on the Galapagos islands?

Darwin observed several key adaptations among the organisms on the Galapagos Islands, particularly in finches, which displayed variations in beak size and shape suited to different food sources. He noted that these adaptations were influenced by the specific environmental conditions of each island, leading to diverse ecological niches. Additionally, he studied tortoises with differing shell shapes and marine iguanas adapted to swimming and foraging in the ocean, all of which contributed to his theory of natural selection. These observations highlighted the role of environmental pressures in driving evolutionary change.