Directional: A process in Natural Selection where a a single phenotype is favored resulting in the allele frequency to shift in a driection continuously.
e.g. The grey hound was breeded for speed and is now one of the fastest types of dog.
Stabilizing: The type of selection where genetic diversity is slowly decreased on a particular trait value.
e.g. Human birth weight: babies of low weight lose heat more quickly and get ill from infectious disease more easily, whereas babies of large body weight are more difficult to deliver through the pelvis.
Disruption: changes in population genetics in which extreme values for a trait are favored over intermediate values.
e.g. The color of a rabbits fur helps it blend in to it's environment. BUT if a different color that doesn't camouflage the rabbit is introduced into the environment, it will be killed because of it's lack of camouflage. This is where disruption comes into play. The rabbits that are camouflaged will breed with the rabbits without any camouflage thus creating babies that are camouflaged.
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