[Amezarak]

Darwin himself noted in the Origin of Species that there is not really any such thing as a "species." It is a poor abstraction we use to describe a group of closely related organisms, but the classifications are necessarily arbitrary and the lines are fuzzy. To visualize this more clearly, imagine that we resurrected every organism that ever lived. It would be easy to say that, say, your cat is felis catus, and so was his father, but scanning back through say, 2^32 ancestors, it would be impossible to point to any ancestor n, compare it with ancestor n + 1, and say this is one species, and that another. Of course, hybridization events make the picture even more complicated. This problem was of course already known at the time, and nothing has changed since, because of the nature of the underlying biological reality.

Thus, there is no distinction at all between "microevolution" and "macroevolution".

[utkarsh858]

https://dictionary.cambridge.org/dictionary/english/species

"set of animals or plants in which the members have similar characteristics to each other and can breed with each other"

Breeding is a criteria for differentiating species and also there is a lot of difference between theory and practice.

[Amezarak]

Do you think lions and tigers are the same species, then? Wolves and coyotes? Horses and donkeys? Camels and llamas?

“Can interbreed” is a fuzzy line too, the probability decreases as genetic distance increases but it doesn’t just suddenly stop. Sometimes very different species can interbreed, and sometimes a small change is enough to make it stop working. Of course, often breeding can be accomplished with human intervention, but never in nature, for simple mechanical or behavioral reasons.