Answer:
Natural selection is a mechanism of evolution. Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time.
Directional
Directional selection is a type of natural selection in which one of the extreme variations in a trait is selected. For example, in a population of giraffes, each individual giraffe has a slightly different neck length. This variation in the trait gives each giraffe a different advantage when it comes to getting food from the tree branches. Giraffes that are on the end of the spectrum with longer necks are better able to reach the food source and thus are better able to survive and reproduce. Over time, the giraffes with long necks will reproduce more and pass on their genes. Thus, future generations of giraffes will tend to have longer necks also. If directional selection persists, eventually this new population can become an entirely new species.
disruptive
Disruptive Selection occurs when both extreme traits in a population are selected. Disruptive selection creates the most variation within a population and is most likely to lead to speciation. Peppered moths in London are an example of a population that underwent disruptive selection. Peppered moths come in colors ranging from white to black, and the peppered moths originally could be found in forests of birch trees, where the environment was light colored. As a result of this, only the white moths blended in and were able to escape predation. However, during the industrial revolution, pollution from factories started to turn the cities black. This darker colored environment created conditions that favored the darker colored moths. Thus, in this time period, both white and black moths, the variation at the ends of the spectrum, were favored.
Stabilizing
Stabilizing selection is the opposite of disruptive selection. Instead of favoring individuals with extreme phenotypes, it favors the intermediate variants. Stabilizing selection tends to remove the more severe phenotypes, resulting in the reproductive success of the norm or average phenotypes.