Types of Natural Selection
Subject:
Biology [1]
Types of Selection.
1 Directional selection occurs when an extreme phenotype is favored; the distribution curve shifts that direction.
a) A shift to dark-colored peppered moths from light-colored correlated with increasing pollution.
b) Drug-resistant strains of bacteria are a serious health threat and represent this type of selection.
c)Increases in insecticide-resistant mosquitoes and resistance of the malaria protozoan Plasmodium to medications are also examples of directional selection.
d)The gradual increase in the size of the modern horse, Equus, correlates with a change in the environment from forest-like conditions to grassland conditions.