Examples of Evolution: Selective Pressures and Adaptation

Natural selection works on individuals within a population, with the end result that a variation that provides benefit to the individual will become more prevalent in the population.  Natural selection is one variable in evolution, but it is not the only type of selection. Other types of selection include artificial, sexual and kin selection. These selective pressures result in adaptions - particular lifestyles or body plans that provide an advantage in a specific environment. 

  • Guppy coloration: Guppies are fresh water tropical fish that are favorites in aquariums because the males are beautifully colored.  In the wild, guppies live in streams where they are the favorite snacks of many larger fish.  John Endler studied guppies in Trinidad and found that the presence of absence of predators influenced the amount of coloring in male guppies.  This is an example of the intersection of two evolutionary forces: natural selection and sexual selection. 


Back to Examples of Evolution »