Galapagos Finches

These are the Galapagos finches that Darwin discovered... they're all finches but have different beaks.  

'As many more individuals of each species are born than can survive, and as consequently there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly profitable to itself... will have better chance of surviving, and thus be naturally selected... The preservation of favourable individual differences and variations, and the destruction of those which are injurious, I have called Natural Selection.'
-Charles Darwin