This homework is due tomorrow!!!!!! Please help me!!!!

Hi there. I don't know if this is too late for you now - but resistance came about through what is called artificial selection. When we treat bacteria with an antibiotic we kill all those bacteria that are not resistant to it. That means that if a few bacteria have mutated a resistance to it (through a mutation in their DNA) they only will survive being treated with that antibiotic - so this is artificial selection. That is why many bacteria are resistant to penicillin - the longer the antibiotic is used the more chance there is that resistance will evolve - as I have explained. Hope that helps - Jon