Darwin's finches common ancestor arrived on the Galapagos about two million years ago,during the time that has passed the Darwin's finches have evolved into 15 recognized species differing in body size, beak shape, song and feeding behavior
Changes in size and form of the beak have enabled different species to utilize different food resources such us insects, seeds, nectar from cactus flowers all driven by Darwinian selection
From 1831 to 1836, Darwin was part of a survey expedition carried out by the ship HMS Beagle, which included stops in South America, Australia, and the southern tip of Africa
At each of the stop, Darwin had the opportunity to study the local plants and animals
Darwin found that nearby islands in the Galapagos had similar but nonidentical species of finches living on them,he noted that each finch species was well-suited for its environment and role
For example species that ate large seeds tended to have large, tough beaks, while those that ate insects had thin, sharp beaks
According to Darwin's idea, this pattern would make sense if the Galapagos Islands had long ago been populated by birds from the neighboring mainland
On each island, the finches might have gradually adapted to local conditions (over many generations and long periods of time)
This process could have led to the formation of one or more distinct species on each island
Darwin developed and refined a set of ideas that could explain the patterns he had observed during his voyage
In his book, On the Origin of Species, Darwin outlined his two key ideas: evolution and natural selection
Natural selection which also known as “survival of the fittest,” is the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits; this leads to evolutionary change

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