A company develops a new weed-killing chemical. When the chemical is first used, it kills nearly all the weeds. After 10 years, nearly all the weeds can tolerate the chemical and survive. Why?

The weeds are starting to resist the chemical and mutate and adapt to the chemical so they can survive.

cramming before a final is bad because it makes a student's stress level higher. students who embrace cramming to get through a final exam week find themselves struggling to perform consistently, once the brain adjusts to prolonged sleep deprivation.