© Public Domain from The Zoology of the Voyage of H.M.S. Beagle, by John Gould. Edited and superintended by Charles Darwin. London: Smith Elder and Co., 1838.
The birds sketched here showcase the diversity of the Galapagos finch population. The finch in the lower left corner lives in trees and eats insects. The one pictured to its right was mistaken for a warbler by Darwin. The top two finches live on the ground and use their heavy beaks to crush the seeds they eat. These finches seem to have evolved from a common ancestor in response to different environmental conditions they encountered on the Galapagos Islands. More recent research, however, indicates that the finch population evolves more quickly to environmental change than can be explained by random mutations. (Unit: 9)