The simple common definition lacks the required precision for a meaningful discussion because the definitions of species as well as sub-species are not always unambiguous. Sort of like using a Lufkin tape rule to measure the molecular distance between the hydrogen and oxygen atom in water. Can't be done.
The common definition of species fails miserably when asexual reproduction is involved. Think virus and bacteria.
Also,consider the following. According to the definition of species that you are basing your tenuous position on, it follows that the common Mallard and the Black duck that are divergent phenotypically and genotypically but can interbreed and produce hybrid viable progeny shared a common ancestor but that a teal and a mallard that do not interbreed are two different ducks that were created simultaneously during genesis and did not arise out of a common ancestor.
So evolution is going on with the Mallard and Black duck but it is not with the teal? A bit confusing.....no?
So when a definition fails to accurately describe what it is supposed to, the definition needs to be modified so that knowledge can be extended.
Where to turn for the required precision? How about applying the everyday tools of molecular genetics? If we can agree that genotype determines phenotype (pretty basic and should not be controversial) we can proceed to define species by something measurable. Chromosomal structure, nucleotide content, stuff like that. With very similar but different organisms, the difference can be at the level gene nucleotide content.
The artificial constructs of micro and macro gets very murky when looked at with a little precision.
If you cannot scientifically support a clear, unambiguous difference between micro and macro in all cases, then in all likelihood, it does not really exist.
Addendum: The points put forth here were pretty much covered by Notropis' earlier posts.
Last edited by carbon12; 11/24/09. Reason: addendum
