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Galapagos FinchesPART IYes, those little sparrow-like birds, are the most incredible lesson in natural selection. There are a total of 14 species of Darwin's Finches (13 in Galapagos, 1 in Cocos Island), and all belong to the Passerine group (finches, sparrows, etc). Look at the beak differences in these Galapagos Finches:
You read it right: their beaks! When you need a specific tool for a specific use, you don't go around trying all the tools until you find the right one...over time, you rather develop a specific one. Simple. It may sound Lamarckian, and from that angle it sure is. But here come Darwinian principles: variation acts as a regulating factor of the truly fit (something unheard of by Lamarck). PART IIThe definition of allopatric and sympatric has to do with where did this making of species took place? Was it in several islands, or was it in one island? To make the story incredibly amazing, the answer is that speciation took place in both scenarios. Wait, it gets better.... Colonization, recolonization, competition, feeding grounds, isolation, ecological setup, nesting habitat, age and altitude of islands, and more, are factors to be considered when understanding Darwin's finches. (I suggest you read The Beak of the Finch by Jonathan Wiener; Pulitzer Prize Winner). If several ecological niches are found (laymen call this "what to eat, where to live"), therefore colonization (and, indeed, recolonization) can become the factory where new species are "made". Add a million years of time, plus natural selection, and voilá...new species. The Galapagos islands feel proud about renaming with a bird species "the Galapagos Finches" that will remain as living proof of evolutionary importance in modern thinking.
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