What is an example of disruptive selection

Disruptive selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values.

Examples. An example of directional selection is fossil records that show that the size of the black bears in Europe decreased during interglacial periods of the ice ages, but increased during each glacial period. Another example is the beak size in a population of finches.

Stabilizing selection in evolution is a type of natural selection that favors the average individuals in a population. … Classic examples of traits that resulted from stabilizing selection include human birth weight, number of offspring, camouflage coat color, and cactus spine density.

Disruptive selection occurs when individuals of intermediate phenotype are less fit than those of both higher and lower phenotype, such that extremes are favored. This may occur if there are two diverse food sources or predators with diverse preferences for, say, size of prey.

In directional selection, a population’s genetic variance shifts toward a new phenotype when exposed to environmental changes. … In diversifying or disruptive selection, average or intermediate phenotypes are often less fit than either extreme phenotype and are unlikely to feature prominently in a population.

Similarities Between Directional and Disruptive Selection

Both increase the allele frequency of the favored phenotypes within the population. However, they may increase or decrease biological phenotypes within a population. The decrease in the number of phenotypes within a population reduces variation.

Disruptive selection: natural selection against the “average”: extremists survive. The gene for PKU is repeatedly introduced to the human gene pool by mutation. Natural selection removes the rare individuals who are homozygous recessive for this trait. … Natural selection and human biology: Sickle cell anemia.

Diversifying (or disruptive) selection: Diversifying selection occurs when extreme values for a trait are favored over the intermediate values. This type of selection often drives speciation. … The result of this type of selection is increased genetic variance as the population becomes more diverse.

Disruptive selection occurs when both extreme traits are favored in an environment. Disruptive selection increases genetic and phenotypic diversity in a population, since more than one phenotype, or physical trait, is favored. As a result, disruptive selection is sometimes called diversifying selection.

Examples of Disruptive Selection

On Santa Cruz Island, disruptive selection was seen causing speciation in the population of finches that resides there. Due to forces of disruptive selection, intermediate beak sizes have been selected against for generations. The resulting population has almost no medium sized beaks.