> > Jim Shields wrote: " the DNA sequence of the organism IS the organism, so > the DNA sequence perforce defines the species. " > Jim, this is so true. I work with DNA or organisms that are not often seen by the naked eyes and there are countless number of species that are only known by their DNA. We know nothing about the organism except for where the DNA was collected (which is often in a core of soil). Your comment is especially true these days when information about organisms are connected through the web and if we can find DNA for it on a public database like GenBank, we know that it exists. DNA is the only universal identifier of an organism that does not require expertise in a taxonomic group. If I want to know what species of snail eats my bulbs, I can just sequence it without needing to contact a snail expert. I'm simplifying things here. There is still a lot we need to work out. We've only been applying DNA to identify organisms for about 20 years. We've got a long way to go to make things good enough for everyone to be able to use. Jim Mc: > "DNA sequences do not define species; rather, they are a consequence of > the existence of species" > You can switch it around by saying "species are a consequence of DNA" and it would still be valid. > Isn't that another way of saying that taxonomy is good at recognizing > entities which have practical purposes? > Apart of the inherent inclination of humans to organize the natural word, taxonomy produces products (=names) that we all can use to exchange information. There is nothing wrong with viewing taxonomy as a practical tool for the end user. > That some forms of life do not seem to fit into the biological species > concept is not a shortcoming of the concept, it simply indicates that not > all forms of life exist as species. > I see it differently. If a concept does not apply to all living organisms equally, it certainly IS a shortcoming. And it is true that perhaps not all forms of life exist as a species, but as a gradient that goes from one point to the next. Nhu