Question

The most likely reason for the development of resistance against pesticides in insects damaging a crop is -
(a)Genetic recombinations
(b)Random mutations
(c)Acquired heritable change
(d)Directed mutations

Answer 1

Pesticide resistance in insects occurs when they show a decreased susceptibility to a pesticide that was previously effective in controlling them. It occurs from exposure to particular substances that brings about intrinsic changes in the insect’s body, and these changes can be passed onto their offspring.

Complete answer:
- Insecticide resistance is defined as a heritable change in the sensitivity of a pest population that is seen in the continuous failure of a substance to achieve the expected level of control when used according to the recommended dosage and formulation for that pest species.
- Insects gain resistance to pesticides by natural selection, which is the differential survival and reproduction due to variation in phenotypes of an individual in a species. The most resistant species pass on their acquired heritable traits to their offspring.
- Resistance in pests can occur due to various factors. For example, shorter generation times develop resistance quicker than others. Pesticides that do not break down easily also cause resistance in insects, even after their application is discontinued.

Additional Information:
- Random mutations can occur in organisms from radioactivity or exposure to chemical mutagens. However, it does not guarantee pesticide resistance.
- Genetic recombinations are the exchange of genetic material between two different organisms. It occurs in eukaryotic cells and it occurs naturally.
- Directed mutagenesis/mutation is a hypothesis that organisms have an innate tendency to evolve in a particular way when faced with environmental stress.

So, the correct answer is ‘acquired heritable change’.

Note: - Resistance may start only towards one pesticide initially, but it has been reported that pests can develop resistance towards multiple pesticides. This is known as cross-resistance.
- Examples of pesticide resistance: 1. In some places in the world, mosquitoes have gained resistance against DDT.
- In some US states, glyphosate-resistant weeds are present in soybean, cotton, and corn farms.