Can you tell me how antibiotic resistance of bacteria demonstrate various principles of evolution?

Evolution: Evolution has to do with a species evolving a way to help it survive better. If a bacteria faces something that either kills it or prevents it from reproducing, it has to come up with a mechanism to overcome that obstacle.It devises a protection, develops a key to unlock a "door" on the cell it's trying to invade - all kinds of different mechanisms to keep it alive and reproducing. It's evolving!