A person will change, but that's not evolution in the sense we're using here.
A dog will produce a dog- that's true. Nobody thinks that a dog will ever give birth to an ear of corn, a goat, or a weasel. That's not what the theory of evolution says.
What it does say is that a dog will give birth to dogs that are not exactly the same as the parents, and not exactly the same as each other. Every new dog is slightly different from its parents and its siblings. Rover is not the same as his father, he's even more different from his grandfather, and he's very different from his great-great-great-great-great-great-grandfather. All these little differences keep adding up- this is how, in a couple of hundred years, we can get very different breeds of dogs from the same stock. If we were to continue breeding dogs separately for another thousand years- say we take a large collection of little dogs (poodles, chihuahuas, etc) and bred them somewhere where they couldn't interbreed with larger canines, and did the same thing with a group of larger dogs (mastiffs, rottweilers, St Bernards, etc), those little changes would continue to add up over the generations. The little dogs would find a different niche and experience different selection pressures than the big ones, so those differences would add up in different ways. You'd wind up with two different breeds that would no longer be able to mate. They'd be different species.
And, yes, I can hear you say "But they're still of the dog kind!" Fine, they're still canines, just like wolves, foxes, and coyotes are. Exactly like wolves, foxes and coyotes, which all descend from dog-like ancestors but experienced different mutations and selection pressures so that they are no longer the same species. Micro-evolution, you call it, over a hundred thousand or million years.
But these creatures have been breeding for more than a mere hundred thousand years. Go back from your dogs and foxes to their ancestor ten million years ago, take away all those hundreds of millions of little microchanges, and you get a rather dog-like ancestor. Go back another thirty million, and take away millions of microchanges, and you get something that was the ancestors of dogs, cats, and weasels. One set of populations came up with differences that add up to "cat", another came up with differences that add up to "weasel". At NO POINT in this development did any dog give birth to a weasel. All the creatures had parents that were very similar (but not identical) to itself, and offspring that were very similar (but not identical) to itself.
