1. Bacteria reproduce by binary fission which produces clones. Offspring are genetically identical to their parent cells so if a parent is resistant and there are no random mutations occurring, the offspring will inherit the resistance and will pass it to all of their offspring. If there is a selection pressure for the resistance, those that already have it will survive and continue to pass it on. Bacteria are also able to exchange genetic material through a sex pilus in a process called conjugation. If this occurs, bacteria might gain resistance without inheriting it but would then pass it to any offspring clones it produces. It is also possible that bacteria could gain resistance by random mutation if the mutation occurs in the location of the bacteria that the antibiotic is targeting. If this occurs, the mutation would again be passed on to any offspring.

2. Bacteria reproduce by binary fission, which is an extreme form of inbreeding because all offspring are clones of their parental cells. If a colony of bacteria is treated with antibiotics, all of the bacteria will die unless there happens to be a few that are previously resistant. Once the non-resistant bacteria have been killed, only the resistant ones are left. If they are able to reproduce, then the entire colony, once it has been re-built, will then be resistant to that drug. In this situation, resistance has been passed on to all the given bacteria very quickly.