Explain what happened genetically in the insect population over time as the insects were exposed to pyrethroids.

The insects developed pyrethroid resistance.

Explanation:

Pyrethroid Insecticides:

Pyrethroids are synthetic derivatives of the natural compounds, pyrethrins, produced by Chrysanthemum plants to prevent insect attacks.Pyrethrins work by locking sodium channels in the cell membrane. This inhibits nerve impulses and paralyses the insect, ultimately resulting in its death. In the 1940s, synthetic pyrethroid insecticides were first used on auricular crops. But till the 2000s, 100 of insect species were resistant. This occurred due to the fact that the allele for pyrethroid resistance increased throughout the population.Pyrethroid resistance developed to enable the insects to survive. Natural selection allowed an exponential transfer of insecticide resistance genes throughout the insect population.Three major mechanisms of resistance were identified by scientists:Increased expression of genes involved in toxin detoxification.Decrease in sensitivity of the target proteins (on which pyrethrins act).Decrease in the insecticide penetration through the cuticle.