How does the development of antibiotic resistance in bacteria provide evidence for evolution?

A population of bacteria will have lots of variation in characteristics due to mutations in the DNA that each bacteria contains. Some of those mutations may allow a bacteria to be resistant to an antibiotic such as penicillin. If the bacteria are exposed to penicillin, then the bacteria which have the resistance mutations will be more likely to survive and reproduce than those without them, and will pass on their resistance to their offspring. This change in the resistance of the population to antibiotics is an example of evolution.Because bacteria reproduce at such a high rate, we can observe and track the evolution of resistance to antibiotics over really short time scales, much shorter than tracking the evolution of characteristics like size in larger species like humans. Furthermore, we can show that antiobiotic resistance evolves as we would expect from Darwin's theory of evolution by natural selection.