industrial melanism

8/8/2019 Industrial Melanism

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` Melanism is the occurrence of an increased

amount of dark pigmentation (as of skin, feathers,

eyes or hair) in an organism, resulting from the

presence of melanin. It is the opposite of albinism, which occur because of a lack of

melanin or other types of pigment.



` Abundism is the occurrence of excessively

abundant dark markings (such as spots, stripes or

other patch types) due to increased dark

pigmentation on the coat, fur or skin of someanimal species.



Melanism is often the result of genetic

mutation, but can result from other

stimuli, such as exposure to abnormal

temperature changes during gestation

which transiently alter gene transcription

or translation.

In the context of diseases, the condition

in which abnormally dark pigmentation of

some tissues occurs is coined

melanosis.



` Melanism related to the process of adaptation is

called adaptive. Most commonly, dark individuals

become fitter to survive and reproduce in their

environment as they are better camouflaged. Thismakes some species less conspicuous to

predators while others use it as a foraging

advantage (for example during night hunting).



Typically adaptive melanism is heritable: A dominant gene (which is entirely or

nearly entirely expressed in the

phenotype) is responsible for the

excessive amount of melanin.Adaptivemelanism has been shown to occur in a

variety of animals, including mammals

(squirrels, many felines, many canids),

reptiles (coral snakes) and insects(peppered moth).



` Industrial melanism is adaptive melanism caused by

anthropogenic alteration of the natural environment

in terms of industrial pollution. As soot, smoke and

other industrial pollutants from factories darken thelandscape and because many organisms rely on

camouflage to avoid predation, this sudden change

in their environment makes them highly vulnerable

to predators..



This creates a strong selective

pressure which will see any organismwith a darker colour much more likely

to survive and contribute to the gene

pool of the next generation. Rare

mutations are hence selected for andover time the population will adjust to a

new equilibrium. Peppered moth

evolution is commonly used as an

example of industrial melanism



` The peppered moth (Biston betularia) is a temperate

species of night-flying moth.

` In Britain and Ireland, the peppered moth is univoltine

(i.e., it has one generation per year), whilst in south-eastern North America it is bivoltine (two generations

per year).

` The lepidopteran life cycle consists of four stages: ova

(eggs), several larval instars (caterpillars), pupae,which overwinter live in the soil, and imagines (adults).

During the day, the moths typically rest on trees, where

they are preyed on by birds.



` The evolution of the peppered moth over the last

two hundred years has been studied in detail.

Originally, the vast majority of peppered moths

had light coloration, which effectively camouflagedthem against the light-colored trees and lichens

upon which they rested.



Biston betularia betulariamorpha typica,

Biston betularia betulariamorpha carbonaria,



However, due to widespread pollution

during the Industrial Revolution inEngland, many of the lichens died out,

and the trees which peppered moths

rested on became blackened by soot,causing most of the light-colored moths,

or typica, to die off due to predation. At

the same time, the dark-colored, or

melanic, moths, carbonaria, flourishedbecause of their ability to hide on the

darkened trees.



Since then, with improvedenvironmental standards, light-

colored peppered moths have again

become common, but the dramatic

change in the peppered moth'spopulation has remained a subject of

much interest and study. This has led

to the coining of the term "industrialmelanism" to refer to the genetic

darkening of species in response to

pollutants.



` 1.WIKIPEDIA

` 2.STRICKBURGER

` 3.DINESH BOOK OF BIOLOGY

industrial melanism

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