Question

Mosquitoes became resistant to the pesticide DDT within 15 years of widespread spraying of the pesticide. Which of the following statements best explains how the resistant mosquitoes arose?

• A. Some mosquitoes experienced a mutation after being exposed to DDT
• B. Some mosquitoes were already resistant to DDT when DDT was first sprayed
• C. DDT is generally a very ineffective pesticide
• D. DDT is not effective against mosquitoes

Answer 1

The correct option is B Some mosquitoes were already resistant to DDT when DDT was first sprayed

Anthropogenic actions refer to the activities that are caused by human beings. This hastens the method of evolution.

Excess use of pesticides and antibiotics has resulted in selection of resistant varieties in a lesser time scale.

Exposure to the DDT killed all the mosquitoes except the ones that are already resistant to it. Hence, the resistant population is selected by nature and a new population of mosquitoes resistant to DDT evolved in very less time.

This is an example of evolution by anthropogenic action.