Abstract: The Galapagos islands are volcanic. They have never been connected to the mainland. The fourteen species of Darwin’s finches fall into four groups: ground finches, tree finches, a warble fineh, and the Cocos finch. All fouvteen species of Darwin’s finches differ from each other in body size and or bill, size and shape. The original colonists of the Galapagos must have arrived by overwater flight from the Central or South American continent. Speciation occurred within each group fairly recently. They were all descended from a singie group of colonist. In fact, Galapagos island differ in the characteristics of their food supplies, therefore adaptation to local food supplies is a sufficient explanation for devergence in Galapagos finches. Interspecific competition for food played a role in the adaptive radiation. Darwin’s finches represent an early stage in the diversification of a group and hence allow us to indentify the causes of the origin of an adaptive radiation. Hawaiian archipelago offers a contrasting example of the more typical condition.

Key words: Galapagos lslands, Darwin’s finches, geographic isolation, niche, adaptative radiation