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How species change More about the finches Darwin’s Finches • 13 different species of finches • Darwin though they were different species of wren, warbler, blackbirds and so on. – Identified as finches in England • Beaks are specialized for the bird to eat different food – Some birds use their beaks to make tools – Some are vampires – Look at page 472 in the textbook Natural selection • The different beaks are useful when the dry season occurs (Darwin visited in rainy season) – The birds become feeding specialist when food is scarce • Beak specialization lets the birds optimize the search for scarce food • Modern biologists today tag the birds and follow them – In drought 1976-1977 biologists saw natural selection at work Bottom line….isolation • Isolating mechanisms – Behavioral isolation – Geographic isolation – Temporal isolation • Finches recap – Founders arrive; geographic isolation occurs; changes in gene pools result; behavioral isolation occurs; competition and natural selection; evolution continues…..