Three Types of Selections

Directional selection is one kind of natural selection that a single phenotype is favored, which cause the alleles' frequency change in one direction.  The greyhound dog can be a perfect example of directional selection because the breeders choose the ancestors of these dogs whose speeds are fast.  Therefore, their offsprings are the fastest dogs.  Stabilizing selection is a type of natural selections in which genetic diversity decreases as the population stabilizes on a particular trait.  An example of stabilizing selection is Siberian Husky, a dog lives in the snow, because they have heavy muscles in their bodies, so these dogs will not sink into the snow.  Disruptive selection is the changes in population genetics, which extreme values for a trait is more favorable than a intermediate values.  The examples of disruptive selections can be based on the different large animals, such as an elephant because the larger animals need more food and oxygen, so these animals can live in a new enviroment even the change is extreme.