Final answer:
Charles Darwin observed variations in beak shapes among finches in the Galapagos, which supported his natural selection theory, showing adaptations that allowed them to survive by efficiently obtaining their specific food sources.
Step-by-step explanation:
When Charles Darwin traveled to the Galapagos, he observed that organisms on the South American mainland were similar to those on the islands but had variations in their beak shapes to help obtain food. In observing the finches across the islands, Darwin noticed that each species had a beak uniquely adapted to their diet and food sources available in their specific habitat. For instance, seed-eating finches possessed strong, thick beaks appropriate for breaking open hard seeds, while insect-eating finches had slender, sharp beaks for catching and eating insects. Through these observations, Darwin developed the concept of natural selection, where beneficial adaptations like beak modifications are passed down, allowing species to better survive in their environment.