Taxonomy question: Are cows and bison separate species?

[Shake]

This isn't a biological question, it's a linguistic one.

Technical terms, such as 'species' exist to help us to understand reality. If they are not serving that purpose in a given context, then we should use other, more useful, words instead.

The words are useful only insofar as they help our understanding. They are not, and should not be allowed to become, a straitjacket on our thought processes. Words do NOT have power, outside the fields of religion and politics (both of which are the inferior, for allowing words to control men, rather than the other way about).

You make a fair point, but there is a biological concept behind the term "species". Because this concept is, by its very nature, 'fuzzy around the edges', it does not lend itself to precise definition. Very broadly a species is a relatively homogeneous group of organisms that is distinct from other such groups, but of course this begs the questions "how homogeneous?" and "how distinct?"

Peez

Absolutely. It's a very useful concept (or perhaps 'set of closely related concepts') that certainly deserves its own word. But at the edge cases, the word can become more of a hindrance than a benefit, and questions such as that in the OP, which simply reflect the limits of the concept, may be misinterpreted as reflecting a nonexistent limit of human knowledge.

This is particularly problematic when religionists are determined to misunderstand the concept of species to suit their own agenda.

It's still a far better word to use than 'kind', as the creationists like to use.