Final answer:
When exposed to antibiotics, bacterial populations with resistant traits become dominant as non-resistant bacteria are eliminated. This results in future generations of bacteria that are uniformly resistant to the antibiotic used. This phenomenon exemplifies natural selection and is aggravated by the overuse and misuse of antibiotics.
Step-by-step explanation:
If only the resistant bacteria remain, the population of bacteria will become uniformly antibiotic-resistant in future generations. This trait will prevail because the antibiotics have eliminated the non-resistant individuals, allowing only those with the resistance gene to reproduce. Over several generations, this resistance will become a characteristic of the entire bacterial population due to natural selection. An example of this process is the increasing resistance to drugs like Vancomycin in hospital settings, particularly in Intensive Care Units.
The mechanism for this change is not new mutations in response to antibiotic application; instead, the genetic variation for resistance already exists within the bacterial gene pool. When antibiotics are used, they kill non-resistant strains, leaving behind those with resistance genes, which then multiply and spread this genetic trait. This is a clear demonstration of evolution through natural selection, where an environmental pressure—antibiotics—selects for the advantageous trait.
Unfortunately, the widespread overuse and incorrect use of antibiotics have exacerbated this issue, leading to the natural selection of resistant forms and the reduction of bacterial diversity that can respond effectively to treatments.