A city was intensively sprayed with the chemical DDT to control houseflies. The number of houseflies was immediately greatly reduced
Each year thereafter, the city was sprayed again, but the flies gradually increased in numbers until 10 years later when they were as abundant as they were before the control program began. Provide an evolutionary explanation of what happened.
The few flies that happened to be born with a genetic resistance to DDT survived and then passed this resistance on to their offspring. Subsequent generations of flies were less and less affected by DDT, and natural selection resulted in a population resistant to the chemical that could proliferate even when DDT was applied.
You might also like to view...
Which of the following are examples of amplification of a hormone signal?
I) Epinephrine initiates an enzyme cascade. II) Steroids bind hormone-response elements in the cell and initiate transcription of many genes. III) A quantity of 0.09 mg of growth hormone leads to a 10,000-mg weight gain in a cow. IV) Different cell types have different receptors capable of binding the same hormone. A) only I and III B) only II and IV C) only I, II, and III D) only II and III E) I, II, III, and IV
Which type of selection would lead to two distinct phenotypes?
A. Stabilizing selection B. Phenotype selection C. Fitness selection D. Disruptive selection E. Directional selection
Which ocean zone extends from low tide to the edge of the continental shelf?
a. Neritic zone b. Intertidal zone c. Abyssal zone d. Aphotic zone
The evolution of bilateral symmetry enabled animals to
A. evolve cephalization. B. evolve feeding organs. C. become motile. D. reproduce sexually.