Stabilizing selection
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Stabilizing selection is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait.
For example, mice that are too small may not be strong enough to burrow underground in cold weather, while mice that are too large may use too much energy keeping warm. If the climate becomes colder, fewer large and small mice will survive to reproduce.
Stabilizing selection operates most of the time in most populations. This type of selection limits evolution by keeping allele frequencies relatively constant. In this way, populations of organisms, such as sharks and ferns, have remained stable for millions of years.
A frequency graph of a trait undergoing stabilizing selection that begins as a bell curve becomes thinner and more steep over time. Template:Biosci-stub