Step-by-step explanation:
Resistance to pesticides can be explained as:
Insects evolve during the time to adapt to the use of insecticides and pesticides to survive the modifications by the natural selection process.
The insects with resistant genes and modifications better over other species survive over the organism having less preferred conditions.
The selective agents cause variation in some species of organisms causing them to adapt to the changed surroundings for survival.
Thus, random variations favour some insects to adapt to changed situations.
Learn more about random variations here: