There are only population groups which change over time and may also split up. So a population group is always the same species... and in fact, like Para said, Species is a just an arbitrary classification we use when looking back over time at various population groups.
The problem with this whole idea is that whenever you split a population group, each new group, while developing new forms, loses some genetic potentials, so the idea that there can be continuous open-ended change is an illusion. Over time the processes that split populations {ABE: and produce new phenotypes} also reduce genetic diversity, which ultimately reaches a point where no further change is possible. It sounds good but it doesn't work. I believe this natural limit to change is the definition of a Kind. Yes, supposedly mutation counteracts this effect, but I think that's mostly a matter of blind faith too.
This message has been edited by Faith, 12-30-2005 01:07 PM