Quick semantic question...
Due to evolution in a macro sense does the word "species" have any real meaning? I was thinking about the recent studies showing that modern humans have Neanderthal DNA but I've always been given the definition of species that two different species are incapable of interbreeding. Or does that mean we are in fact two breeds of the same species?
Reference: Biology, 6th Ed. (Campbell & Reece)
Modes of Speciation:
a) Allopatric speciation: a population forms a new species while geographically isolated from its parent population. Example: A group of trees is separated in time by a river, and speciation occurs due to (perhaps) exogenous environmental factors.
b) Sympatric speciation: a small population becomes a new species without geographic separation from its parent population. Example: A group of trees is left in tact, but speciation occurs due to (perhaps) endogenous and exogenous factors.
Hope this helps with your question.