Editing Directional selection (section)

=== Peppered moths ===
[[File:Biston betularia (4777708667).jpg|thumb|Peppered moth with dark phenotype that was positively selected for during the Industrial Revolution. ]]
[[File:-1931- Peppered Moth (Biston betularia) (49943032886).jpg|thumb|Peppered Moth with white phenotype that was negatively selected for during the Industrial Revolution.]]
A significant example of directional selection in populations is the fluctuations of light and dark phenotypes in [[Peppered moth|peppered moths]] in the 1800s.<ref>{{Cite web |title=Peppered Moth |url=https://globalchange.umich.edu/globalchange1/current/labs/Lab5_PepperedMoth/PepperedMoth.htm |access-date=2024-03-24 |website=globalchange.umich.edu}}</ref> During the industrial revolution, environmental conditions were rapidly changing with the newfound emission of dark, black smoke from factories that would change the color of trees, rocks, and other niches of moths.<ref>{{Cite web |title=Peppered Moth and natural selection |url=https://butterfly-conservation.org/moths/why-moths-matter/amazing-moths/peppered-moth-and-natural-selection |access-date=2024-03-24 |website=butterfly-conservation.org |language=en}}</ref> Before the industrial revolution, the most prominent phenotype in the peppered moth population was the lighter, speckled moths. They thrived on the light birch trees and their phenotype would provide them with better camouflage from predators. After the [[Industrial Revolution]] as the trees become darker with soot, the moths with the darker phenotype were able to blend in and avoid predators better than their white counterparts. As time went on, the darker moths were positively directionally selected for and the allele frequency began to shift due to the increase in the number of darker moths.<ref>{{Cite journal |last=Saccheri |first=Ilik J. |date=October 2008 |title=Selection and gene flow on a diminishing cline of melanic peppered moths |journal=Proceedings of the National Academy of Sciences |volume=105 |issue=42 |pages=16212–16217 |doi=10.1073/pnas.0803785105 |doi-access=free |pmid=18854412 |pmc=2571026 |bibcode=2008PNAS..10516212S }}</ref>