Mosquitoes resistant to the pesticide DDT were first noted in India in 1959. DDT

Question

Mosquitoes resistant to the pesticide DDT were first noted in India in 1959. DDT-resistant mosquitoes are now found throughout the world. The graph shows the results of a DDT spray program, in which mosquitoes were considered resistant if they did not die within 1 hour of a 4% DDT dosage. Which scenario best explains the relatively quick increase in DDT resistance among the mosquito population?

a

The mosquitoes who are not DDT-resistant leave the area where DDT is applicated and DDT-resistant mosquitoes move into the area.

b

The application of the pesticide causes the mosquitoes to change their DNA such that they develop resistance to DDT.

c

A few DDT-resistant mosquitoes were present at the start of DDT application, and natural selection increased their frequency.

d

DDT-resistant mosquitoes continue to migrate from India (transported by wind, trains, planes) and move into other parts of the world.

Explanation / Answer

A few DDT-resistant mosquitoes were present at the start of DDT application, and natural selection increased their frequency.

This is the most correct answer that explains best about the resistance in DDT and relatively quick increase in DDT resistance among the mosquito population. It is the natural phenomenon that due to increase in DDT spray there will be death of the most of mosquitoes, but few of them remains alive, due to some alteration in the DNA of any other physiological chracter.

Then this population breeds and increase in the no. and consequently the population of the resistant mosquitoes replaces the non resistant ones.

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