Over time, bacteria have become increasingly resistant to antibiotics. Explains this in terms of natural selection.

Bacteria with antibiotic resistance gene/s are favored by natural selection.

Explanation:

The presence of one or more antibiotic resistance genes in the bacteria becomes an adaptive trait in the presence of antibiotics in the surroundings. These bacteria have higher chances of survival and reproduce more to produce more progeny as compared to the bacteria that lack any antibiotic resistance gene. Therefore, the frequency of antibiotic-resistant genes in the population increases over the generations. Here, the increased fitness of bacteria having antibiotic resistance gene/s in the presence of antibiotics represents a natural selection.