Final answer:
Antibiotic resistance in bacteria occurs due to natural selection, where genetic variations that provide resistance are selected for when antibiotics kill off non-resistant bacteria. This leads to a population dominated by resistant strains, a problem exacerbated by the overuse and incorrect use of antibiotics. The resistance traits were already present in the gene pool, not induced by the antibiotics.
Step-by-step explanation:
How Antibiotic Resistance Evolves Through Natural Selection
The development of antibiotic resistant bacteria is a worrying example of evolutionary change in action, primarily through the process of natural selection. This phenomenon occurs when bacteria with genetic variations that confer resistance to antibiotics survive and continue to reproduce while the non-resistant ones are killed off by the drug. Since these resistant bacteria are able to survive the antibiotic, they reproduce and pass on the resistant trait to their offspring, leading to a population of bacteria where all individuals are resistant to the antibiotic.
One of the key contributors to this problem is the overuse and incorrect use of antibiotics, such as not finishing a prescribed course. This leads to situations where bacteria that can tolerate the antibiotic drugs survive and thrive. Over time, as these bacteria continue to multiply, the proportion of resistant strains in the population increases.
It is crucial to understand that the genetic variations that natural selection acts upon were already present in the population, not a direct response to the presence of antibiotics. Mutations creating resistance occur by chance and those beneficial mutations are then selected for. This adaptation makes pathogens that were once easily treatable with antibiotics, such as tuberculosis and pneumonia, into emerging threats due to increased resistance.