Question

A small town on the edge of the Caddo Lake National Wildlife Refuge was heavily infested with mosquitoes. The town was sprayed with an insecticide for a period of several months. The graph shows the results of the daily counts of the mosquito population.

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Which of the following statements best explains why some mosquitoes survived after the first spraying?

A.
Only mosquitoes born after spraying started had a genetic mutation that made them resistant to the insecticide.

B.
Some mosquitoes had a genetic mutation that made them resistant to the insecticide.

C.
Only mosquitoes from the previous generation had a genetic mutation that made them resistant to the insecticide.

D.
All mosquitoes had a genetic mutation that made them resistant to the insecticide.

Answer 1

The statement that best explains why some mosquitoes survived after the first spraying is:

**B. Some mosquitoes had a genetic mutation that made them resistant to the insecticide.**

This option correctly indicates that the survival of some mosquitoes is due to the presence of a genetic mutation for resistance in a subset of the existing population before the spraying began. This is a common phenomenon in pest control, where not all individuals of a population are equally susceptible to an insecticide, leading to the survival of those with resistance genes.