Editing Directional selection (section)

=== Finch beak size ===
[[File:Darwin's finches by Gould.jpg|thumb|Darwin's finches with different sized beaks that were suited for different seed types]]
Another example of directional selection is the beak size in a specific population of [[Finch|finches]]. Darwin first observed this in the publication of his book, ''[[On the Origin of Species]],'' and he details how the size of the finches beak differs based on environmental factors. On the [[Galápagos Islands]] west of the coast of [[Ecuador]], there were groups of finches displaying different beak phenotypes.<ref>{{Cite web |last=Burrows |first=Leah |date=November 2021 |title=For Darwin's finches, beak shape goes beyond evolution |url=https://seas.harvard.edu/news/2021/11/darwins-finches-beak-shape-goes-beyond-evolution |website=Harvard School of Engineering}}</ref> In one group, the beaks ranged from large and tough to small and smooth. Throughout the wet years, small seeds were more common than large seeds, and because of the large supply of small seeds the finches rarely ate large seeds. During the dry years, neither the small or large seeds were in great abundance, and the birds trended towards eating larger seeds. The changes in diet of the finches based on the environmental wet and dry seasons affected the depth of the birds’ beaks in future generations. <ref>{{cite book |last1=Campbell |first1=Neil A. |url=https://books.google.com/books?id=9pqXQgAACAAJ |title=Biology |last2=Reece |first2=Jane B. |publisher=Benjamin Cummings |year=2002 |isbn=978-0-8053-6624-2 |edition=6th |pages=450–451}}</ref> The beaks most beneficial to the more plentiful type of seed would be selected for because the birds were able to feed themselves and reproduce.