![]() ![]() For example, seed-eating finches had stronger, thicker beaks for breaking seeds, and insect-eating finches had spear-like beaks for stabbing their prey.įigure 1: Darwin observed that beak shape varies among finch species. Upon further study, he realized that each finch’s varied beaks helped the birds acquire a specific type of food. Darwin imagined that the island species might be species modified from one of the original mainland species. He observed that these finches closely resembled another finch species on the South American mainland. The species on the islands had a graded series of beak sizes and shapes with very small differences between the most similar. For example, the ground finches inhabiting the Galápagos Islands comprised several species with a unique beak shape (Figure 1). On these islands, Darwin observed species of organisms on different islands that were clearly similar, yet had distinct differences. ![]() Darwin’s journey, like Wallace’s later journeys to the Malay Archipelago, included stops at several island chains, the last being the Galápagos Islands west of Ecuador. Wallace traveled to Brazil to collect insects in the Amazon rainforest from 1848 to 1852 and to the Malay Archipelago from 1854 to 1862. Beagle, including stops in South America, Australia, and the southern tip of Africa. From 1831 to 1836, Darwin traveled around the world on H.M.S. Importantly, each naturalist spent time exploring the natural world on expeditions to the tropics. In the mid-nineteenth century, two naturalists, Charles Darwin and Alfred Russel Wallace, independently conceived and described the actual mechanism for evolution. ![]()
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