How did diversity of life on our planet form? How does it maintain itself? Species concept is most certainly a very convenient construct for biologists who are trying to understand life. Rightly so, Charles R. Darwin titled his masterpiece as On the Origin of Species for the concept was crucial in developing a theory that is central to biology. The species argument is quite parallel to that of transitional fossils. Both terms are plastic and represent data points along a continuum. By many, the term transitional fossil is used to define landmark fossils that help us anchor nodes of the evolutionary tree. However, to be exact, EVERY fossil on earth represents a transitional fossil!
Filmed by Christina Choate, the faculty of Montana State University entomologist Michael Ivie, ecologist Steven Kalinowski, geneticist Norm Weeden, paleontologist David Varricchio, microbiologist Dave Ward, mycologist Cathy Cripps, anthropologist Mike Neeley, ornithologist David Willey, discuss the concept. They describe difficulties on how to define species in their scientific fields. Later they explain possible methods (DNA sequencing, morphology) to resolve the species problem.
This documentary is a 2011 project for masters degree program in the School of Film and Photography of Montana State University-Bozeman.
Additionally, you can watch this very friendly lecture from the Khan Academy explaining the species concept as a part of the free biology curriculum: