The emergence of antibiotic-resistant bacteria is an example of natural selection, a fundamental process in the evolution of living organisms. In a simplified manner, natural selection occurs when organisms with advantageous traits, such as the ability to survive or reproduce more successfully in a particular environment, have a higher chance of passing on those traits to their offspring. As a result, over time, the overall genetic composition of a population changes in response to the challenges and selective pressures of its environment.

In the case of antibiotic-resistant bacteria, the introduction of antibiotics represents a new selective pressure that favors the survival and reproduction of bacteria that have acquired genetic mutations or acquired genes allowing them to withstand or even thrive under antibiotic exposure. Bacteria that cannot withstand the antibiotic pressure die, and bacteria with antibiotic resistance have a greater chance of survival and reproduction, passing their resistant traits on to their offspring.

The evolution of antibiotic resistance has been driven by both mutation and horizontal gene transfer, which allows bacteria to acquire resistance genes from other bacteria in their environment. The widespread use of antibiotics in modern medicine and agriculture has led to a significant increase in the development of antibiotic resistance. This is due to the strong selective pressure on bacteria to acquire or develop resistance, leading to the emergence of more and more resistant bacterial strains.

As a result, the evolution of antibiotic-resistant bacteria is an example of natural selection at work. Bacteria that are able to survive and reproduce in the presence of antibiotics are more likely to pass on their resistance genes to their offspring, leading to the emergence of resistant populations. This phenomenon is particularly concerning because it limits the effectiveness of antibiotics, making it more difficult to treat bacterial infections.