I've been looking for this example I knew about and found it on a BBC educational page. IMO it's an excellent example of how evolution works:

Evidence for evolution - rapid changes

"Rapid changes in species have been observed. These support the theory of evolution.
Peppered moths
Before the industrial revolution in Britain, most peppered moths were of the pale variety. This meant that they were camouflaged against the pale birch trees that they rest on. Moths with a mutant black colouring were easily spotted and eaten by birds. This gave the white variety an advantage, and they were more likely to survive to reproduce.
Airborne pollution in industrial areas blackened the birch tree bark with soot. This meant that the mutant black moths were now camouflaged, while the white variety became more vulnerable to predators. This gave the black variety an advantage, and they were more likely to survive and reproduce. Over time, the black peppered moths became far more numerous in urban areas than the pale variety."

I think it's a wonderful example of how evolution works. Absolutely convincing.

That is true and even near relatives such as horses and donkeys always produce sterile offspring if they mate successfully.