Final answer:
Darwin learned that Galápagos tortoises had adapted different shell shapes based on their environments, leading to his ideas on natural selection and adaptive traits.
Step-by-step explanation:
The important information about the Galápagos Islands tortoise that Darwin learned was related to their shell characteristics. The giant tortoises displayed different shell shapes related to their feeding habits and environment. On islands with tall shrubs and vegetation, tortoises evolved with saddle-shaped shells and longer necks, which allowed them to reach and eat the plant leaves above their heads. In contrast, tortoises living on islands with more ground-level vegetation had dome-shaped shells and shorter necks suited for eating plants near the ground. These observations were pivotal for Darwin, leading him to hypothesize that organisms develop specific adaptive traits over time driven by their environments. Hence, the tortoises' shell shapes were clear evidence that environment can influence the evolution of a species, supporting the mechanism of natural selection.