In a region where malaria is common, a drug is frequently us…
In a region where malaria is common, a drug is frequently used to treat infections. The parasite population contains two types: one with a mutation that makes it resistant to the drug, and one that is susceptible. The resistant parasites survive drug treatment, while susceptible parasites mostly die. Over several generations, the frequency of the resistant type increases. Which of the following statements best explains this phenomenon in terms of natural selection and fitness?