Perhaps in the case I describe above simply comes under the umbrella of adaption, not evolution. As the theory of evolution encompasses the gradual increase of complexity of life itself, as opposed to witnessing gradual changes of variants > speciation in animals. But I fail to see the difference, in all honesty.

I suppose we can’t observe a dinosaur evolving into a bird, so I guess that’s the difference.

I am curious though, what would we call the fact of adaption along with the observable differences and incompatibilities between species who can’t reproduce with their former relatives? How else would you describe that as fact without utilising evolutionary terminology?