Darwin's Finches

Natural Selection

About Natural Selection and Darwin's Finches

Darwin's Finches are an excellent example of how a species adapts to its environment and sub-species are created through isolation. These sub-species are the result of being exposed to different environmental factors and niches. Isolation also prevents the finches from interbreeding with other sub-species keeping their gene-pools separate.

In different environments, different characteristics of the finch are favorable - like beak shape and size. Finches that possess unfavorable variations are unable to reach sexual maturity leaving behind the 'fittest' individuals to reproduce.

Gradually, Adaptive Radiation occurs, creating a sub-species. In this case there are 13 different species of the Galapagos finch including:
  • Six species of ground finches
  • Three species of tree finches
  • One woodpecker finch
  • One vegetarian finch
  • One mangrove finch and
  • One Coco Island finch
This process is referred to as 'Natural Selection' which leads to the evolution of a species.

Natural Selection Stages

  1. Within a species there is variation.
  2. Not all individuals are able to reach sexual maturity.
  3. The offspring of the surviving individuals inherit the favorable trait.
  4. The favorable trait becomes common in the population, eventually the unfavorable trait is bred out.
Galapagos: the finches (4/7)

Different Beaks of Finches as a result of Natural Selection

All 13 species of finch evolved differently depending on what part of the Galapagos Islands they lived on due to different food sources, rainfall and other factors. Over many generations, the species adapted to feed in different ways through the process of Natural Selection. Beak shape and size is a major factor in a finches ability to survive e.g. larger beaks are beneficial in times of drought where the seeds available are tougher; whereas smaller beaks can be seen in areas of high rainfall where small, moist seeds are plentiful.
  • Grub eaters: thin extended beaks
  • Bud and fruit eaters: claw-like beaks
  • Seed eaters: crushing beaks
  • Insect eaters: sharp grasping beaks
  • Leave eaters: parrot-like beak
  • Tool using Finches: thin extended beaks