From his observations in the oceanic islands like the galapagos, darwin felt that:

The Galapagos Islands is an archipelago of 13 major and 100 smaller islands. It is located in the Pacific ocean near the west coast of Venezuela. In old Spanish galapagos meant tortoise. These islands affected Darwin's thoughts about evolution of species. In 1835 he spent five weeks on the islands. While on island he discovered species of finches and observed that species of finches varied from island to island. It helped him to elaborate his ideas about natural selection and examine the evolutionary changes of the finches.