How does an insect species become resistant to an insecticide?
the more exposure an insect has to the insecticide the weaker the effects of it are.
after an exposure if the insect survives, it mutates to become resistant if it encounters it again.
there are some offspring already resistant to the insecticide's effects that survive and reproduce.
after exposure, all the reproductive cells have mutated to become resistant for the next generation.

Which of the following observation darwin shape his concept of descent with modification? a) species diversity declines farther from the equator. b) fewer species live on islands than on the nearest continents. c) birds live on islands located farther from the mainland than the bird's maximum nonstop flight distance. d) south american temperate plants are more similar to the tropical plants of south america than to the temperate plants of europe. e) earthquakes reshape life by causing mass extinctions.