Can different breeds of dogs be considered different species?

You cannot consider different breeds of dogs to be representatives of different species. There are several criteria by which one or another representative can be attributed to different types.

So, if we rely on the morphological criterion, then all breeds of dogs have a similar structure, both internal and external, by individual signs we can easily distinguish a dog, for example, from a cat.

According to the biochemical criterion, it can be determined that the intracellular composition of hormones, enzymes and other biologically active substances in dogs is the same.

And the most convincing proof is that representatives of all breeds of dogs have the same chromosome composition and, when crossed, can produce fertile offspring.