All of them. They came from an original finch and then they evolved to survive on whichever island they were on.
allopatric speciation
allopatric speciation
adaptive radiation
The type of speciation that occurred among the Galapagos Islands finches is called "allopatric" speciation. Allopatric comes from roots meaning "other country". The immigrant finches, and many other birds and animals, were very isolated from other populations of the same species on the individual Galapagos Islands. The finches developed into at least 13 different species of finch on the islands.
Directional Selection
Every type of bird was a finch, but the genetics of each bird varied upon which island he was on. So he made the theory of evolution explaining how the original finches evolved into having different beaks, colors, eyes, and sizes. Again each of those varied depending on the island.
Famously Charles Darwin studied some finches that he collected when he visited the Galapagos Islands during his voyage on the Beagle. He preserved the specimens he had collected and studied them when he returned to England. He used his observations of the variations in these finches as part of his evidence supporting his theory of evolution. He also studied the breeding of pigeons and domestic poultry.
Charles Darwin watched and studied many animals well on the Galapagos Islands, But the most talked about is a species of bird referred to as Finches. This is the bird that led to Darwin being credited with the theory of evolution by natural selection. These finches probably descended from one type of ancestor and then, due to isolation and through chance, different climates and natural forces such as food availability and type, they evolved into thirteen different types of finches. The process of their evolution would probably have begun with immigrants from the mainland. As they dispersed to different islands, new populations would be formed. Every time these satellite populations dispersed, there would be greater difference between the individual species.
Darwin observed that small birds on the Galapagos islands differed in the shape of their beaks.The seeds that were left on the island were harder so the birds beaks evolved and became stronger and harder.
Geographic IsolationSpeciation in the Galápagos finches occurred by founding of new populations, geographic isolation, gene pool changes, reproductive isolation, and ecological competition.
Every type of bird was a finch, but the genetics of each bird was different on every island :)
These birds, although nearly identical in all other ways to mainland finches, had different beaks. Their beaks had adapted to the type of food they ate in order to fill different niches on the Galapagos Islands. Their isolation on the islands over long periods of time made them undergo speciation (form new species).Darwin wrote about his travels in the book The Voyage of the Beagle and fully explored the information he gained from the Galapagos Finches in his most famous book On the Origin of Species.It was in that publication that he first discussed how species changed over time.