How did Charles Darwin's visit to the Galapagos Islands help form his ideas of natural selection?

Charles Darwin's visit to the Galapagos Islands in 1835 provided him with critical observations of diverse species that had adapted to the unique environments of the islands. He noted variations among finches, tortoises, and other animals, which suggested that species were not fixed but could change over time based on their surroundings. These observations led him to formulate the idea of natural selection, where organisms better adapted to their environment are more likely to survive and reproduce. This concept became a cornerstone of his theory of evolution, articulated in his seminal work, "On the Origin of Species."