Antibiotics don't create resistance; they kill vulnerable microbes and leave resistant ones to multiply. Every dose is a selection event. Raise the antibiotic pressure and watch how it shifts the population toward resistant strains.
Raise the antibiotic pressure. Watch which cells are left to divide.
Vertical gene transfer is the inheritance of resistance from parent to offspring during cell division. Once a bacterium survives antibiotic exposure, it passes resistance genes to all descendants. This is classic Darwinian selection: resistant microbes reproduce, susceptible ones die. Over successive generations, the resistant lineage dominates the population. Vertical transfer alone can shift a community toward resistance in days under sustained antibiotic pressure.
Resistance is selected for, not created — antibiotics don't cause mutations; they kill off vulnerable microbes and let the naturally resistant survivors take over the population — which is why cutting unnecessary antibiotic use slows the spread of resistance.