Actually there is more to it than that.
http://dictionary.reference.com/search?q=species Beyond that all you have to ask yourself is: "How do new secies form?"
Do not chimps and humans supposedly have a common ancestor? Could it have been that at some point our ancestors could have been called different sub-species?
The point is that there is no such thing as any of these terms if you dont want to accept them; because you can pick them apart, just like you can pick many human scientific and social concepts apart. Even chemical bonding theories, the definitions of acids and bases and other concepts and categorzations are not immune. But it does not mean these concepts and categorys have no utility or truth to them.