Solution:-
A classical example of natural action is provided by the peppered lepidopterous insect, biston nitularia. This lepidopterous insect with its light-weight colored wings dotted with spots emulsified well with lichens growing on the homes and tree trunks on that it fresh. the sunshine colored lepidopterous insect as seen in sizable amount because it was well hid whereas resting on homes and tree trunks. this case was discovered during this space before the commercial revolution. however when age in Manchester, the complete scenario modified. The pollution during this space caused the death of lichens and darkening of the tree trunks with soot.
Natural selection acted through the agency of the birds and lightweight colored lepidopterous insect simply became the prey. So, the dark type of lepidopterous insect survived higher, left additional offspring’s and virtually nearly replaced the sunshine type. This development has been known as industrial melanism..