Industrial melanism refers to the dark pigmentation that evolved in some insects
ID: 31902 • Letter: I
Question
Industrial melanism refers to the dark pigmentation that evolved in some insects giving them protective coloration on vegetation darkened by soot in heavily industrialized areas prior to air pollution regulation. Assume that in one heavily polluted area near Birmingham, England in 1956, 79% of the moths of the species Biston betularia were black due to the presence of a dominant gene for melanism. Estimate the frequency of the dominant allele in this population, and the proportion of black moths that are heterozygous.
Explanation / Answer
The evolution of the peppered moth is an evolutionary instance of colour variation in the moth population as a consequence ofIndustrial Revolution. Specifically, it is a concept of increase in number of dark-coloured moths due to industrial pollution, and reciprocal decrease of the population under clean environment. Hence, the phenomenon is called industrial melanism. It is a first recorded and experimented case of Charles Darwin's natural selection in action, and remains as a classic example in the teaching of evolution.
The dark-coloured or melanic moths (carbonaria variety) were not known prior to 1811. After field collection in 1848 fromManchester, an industrial city in England, it was found to increase drastically. By the end of the 19th century it completely outnumbered the original light-coloured type . Its evolutionary importance was only speculated during Darwin's lifetime.
the allele for dark-bodied moths is dominant, while the allele for light-bodied moths is recessive, meaning that the typica moths have a phenotypethat is only seen in a homozygous genotype ,, and never in a heterozygous one. This helps explain how dramatically quickly the population changed when being selected for dark colouration.
The peppered moth Biston betularia is also a model of parallel evolution in the incidence of melanism in the British form and the American form, as they are indistinguishable in appearance. Genetic analysis indicates that both phenotypes are inherited as autosomal dominants. Cross hybridizations indicate the phenotypes are produced by isoalleles at a single locus.