That’s a very simple truth, but it will never stop people from telling you that insects are “evolving” resistance to insecticides or bacteria are “evolving” resistance to antibiotics. The mutation that confers resistance to such things also results in a weaker organism under normal circumstances. Only when they are given an unusual advantage (such as the introduction of pesticides and antibiotics) are they able to reproduce.
Not sure I follow you but that is textbook evolution. Also, mutations don’t always result in a weaker organism that can’t reproduce other than under those circumstances. Mutations are simply changes, some are weaker, some aren’t.
Um...that IS the very definition of “evolution”.
A random change occurs, it proves beneficial under the circumstances, those with it breed profusely while those that don’t have it die off, leaving one population to replace the other.