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  • "Apperance of melanised moths post - industrialisation in England is a classic example of evolution by natural selection." Explain.      

"Apperance of melanised moths post - industrialisation in England is a classic example of evolution by natural selection." Explain.

 

 

 

 
 
 
 
 

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In a collection of moths made in England before industrialization was set in (1850’s), it was observed that there were more white-winged moths on trees than dark-winged or melanized moths. However, in the collection carried out from the same area, but after industrialization, (1920), there were more dark-winged moths in the same area, i.e., the proportion was reversed. The explanation put forth for this observation was that ‘predators will spot a moth against a contrasting background’. During post-industrialization period, the tree trunks became dark due to industrial smoke and soots. Under this condition the white-winged moth did not survive due to predators, dark-winged or melanized moth survived. Before industrialisation set in, thick growth of almost white-coloured lichen (industrial pollution indicators) covered the trees - in that background the white-winged moth survived but the dark-coloured moth were picked out by predators. Hence, moths that were able to camouflage themselves, i.e., hide in the background, survived. This understanding is supported by the fact that in areas where industrialisation did not occur e.g., in rural areas, the count of melanic moths was low. This showed that in a mixed population, those that can better-adapt, survive and increase in population size. Remember that no variant is completely wiped out.

Posted by

Priyanka Kumari

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