Question

The excessive use of pesticides has only resulted in the occurrence of more resistant varieties of pests rather than their complete eradication. How can you link this with Darwin's theory of Natural Selection and Evolution?

Answer 1

$1$. When pesticides are used in excess, the pest species get used to it and become resistant to it which is a trait developed by them in their struggle for existence and trying to survive.
$2$. Only these resistance individuals reproduce, passing on their resistance to their offspring. Through this process of natural selection, the pest population gradually develops resistance to the pesticide. In each generation the percentage of insecticide resistant individuals increases.