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IMSO 2006 Science – Taiwan Selection First Round Theory Question 14

IMSO Science · IMSO 2006 Science – Taiwan Selection First Round Theory

Question 14

Base your answers to questions 40 and 41 on the information below and on your knowledge of biology. A small village was heavily infested with mosquitoes. The village was sprayed weekly with an insecticide for a period of several months. The results of daily counts of the mosquito population are shown in the graph below.

*Editorial note: the source labels this passage 40 and 41; it applies to questions 14 and 15 here.*

Question illustration

Which statement best explains why some mosquitoes survived after the first spraying?
  1. Some mosquitoes were adapted to the climatic change that occurred over the several-month period of spraying.
  2. All of the mosquitoes contained DNA unique to the species.
  3. The spraying of the insecticide represented a change in the environment to which all adult mosquitoes were adapted.
  4. A natural variation existed within the mosquito population.