European rabbits were introduced to Australia in 1859. The rabbits reproduced rapidly in their new environment, displaced other
animals and overgrazed vegetation. In an attempt to reduce the rabbit population, a deadly virus was introduced in 1951. When the virus was first introduced, the rabbits died in large numbers, but the death rate decreased over time. What statement best explains the decrease in the rabbit death rate? A) The virus had a short life span and died out with the rabbits. B) Natural selection favored rabbits that were resistant to the virus. C) The rabbits died of natural causes and the introduced virus did not work. D) Young rabbits exhibited a learned behavior and began to avoid being infected by the virus.
B) Natural selection favored rabbits that were resistant to the virus
Explanation:
Most likely, virus resistance occurred over time, as a consequence of mutation. Individuals that carried the resistance mutation become favourable by natural selection.
Natural selection is evolutionary mechanism which favours traits of an organism that help him survive and reproduce (increase organism's fitness). In the example above, resistant rabbits that survived had the favorable trait (resistance) by natural selection.
