Example Mechanism of evolution 1. As habitats change, populations of northern pine trees that were once separated can now exchange pollen. This exchange of genes between populations is allowing the previously isolated gene pools to mix. 2. A sudden volcanic eruption kills many members of a population of elk. By chance, the individuals that remain do not have the same mix of genes as the original population effect 3. Although millions of praiie chickens once roamed the Midwest, their numbers founder effect dwindled to only 50 individuals in the 1990s. These few individuals have since produced a larger population. The genetic variation among the current population is quite low sexual selection 4. Insecticide resistance among mosquitoes is spreading around the world after mutations that originate in one population are spread to other populations through matings gene flow 5. Researchers discovered that female gray tree frogs prefer to mate with males who sound the longest mating calls 6. Tristan da Cunha is a remote island in the Atlantic Ocean. In 1814, 15 people formed a colony there, one of whom carried a rare gene for blindness The frequency of this gene is now 10 times higher on the island than on the mainland from which the settlers arrived

In population genetics, gene flow is often referred to as gene migration or allele flow. It involves transfer of genetic variation from a population to another population. If the level of gene flow is abundant in high quantity, then the two populations are regarded to have corresponding allele frequencies and can be considered to be a single population.

Genetic drift by bottleneck effect

The bottleneck effect is an extreme example of genetic drift that occurs when the amount of a population is seen to undergo a huge decrease. Certain situations like natural disasters (earthquakes, floods, fires, volcanic eruption) can swiftly reduce a population, leading to the death of a lot of indviduals with a minimal number of random assortment of survivors.

Bottleneck effect:

This is a sharp decline of a population's gene pool due to an environmental, or human-influenced, change

Sexual selection:

Sexual selection is a kind of natural selection where members of one biological sex prefer to copulate with mates of the other sex to mates of its own sex. It is a form of intersexual selection, and compete with its own sex members over the opposite sex members.

Founder effect:

The founder effect is a decline in genetic variation that occurs when a little subset of a large population is employed to set up a new colony. It often times is involved in the emergence of new species.