Final answer:
The development of drug-resistant bacterial strains is attributed to natural selection, where mutations in bacteria giving resistance to antibiotics are selected for and propagated.
Step-by-step explanation:
The widespread use of antibiotics has led to the development of drug-resistant bacterial strains due to the process of natural selection. In the presence of antibiotics, bacteria that have specific mutations allowing them to survive can continue to grow and reproduce. These resistant bacteria then become more common in the bacterial population, leading to strains that standard antibiotics can no longer effectively treat.
Mutations can arise in bacteria that give them the capability to survive in environments containing antibiotic drugs. Over time, these mutations, which confer resistance, are passed down to future generations of bacteria. This leads to the development of antibiotic-resistant strains, which can spread between individuals, making the treatment of bacterial infections increasingly difficult. Thus, the overuse of antibiotics accelerates the process of evolution through natural selection, enhancing the spread of resistance within bacterial communities.