Transcript How species change

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…..