Taxonomic system types
Taxonomic systems employed in the past or at the present can be classified as artificial systems and natural systems. In creating artificial systems, systematists attempted to classify organisms for practical and didactic purposes. As long as only a few species were known, systematists tried basically to create, not a generally valid system, in which it would be possible to also classify newly discovered organisms, but rather a determination scheme that would make it possible to differentiate the members of the individual known species. Only with an increasing number of discovery voyages and the recognition of the enormous biodiversity in newly discovered countries did it become apparent that there are fundamental differences between the determination scheme and the taxonomic system.
Some artificial systems classified organisms on the basis of various combinations of a small number of, where possible, universally occurring traits, while others used a great many traits for classification, where the groups of these traits could differ from one taxon to another. An artificial system based primarily on the basic cell shape and affinity for certain dyes was used until recently for classification of bacteria. Even today, artificial systems remain a basis for the creation of determination keys (determination schemes) for the individual groups of organisms. Their closed nature is a great disadvantage. An artificial system only allows classification of organisms that were known at the time of creation of the particular system. As soon as a new species appears, its proper assignment need not be possible in the majority of cases. An originally unknown species would either be classified under some other species or a suitable category would be lacking in the system. Another great disadvantage of artificial systems lies in their subjectivity. A single group of organisms can be classified on the basis of other traits into a completely different system of taxa, where the selection of traits is a matter of the subjective decision of the systematist.
Natural systems attempt, not only to meaningfully classify organisms for practical and didactic purposes, but also, in creation of the individual taxa, to reveal and especially respect the natural, objectively existing relationships amongst the created taxa. The natural system has three basic advantages. Primarily, the natural system is open, which permits it to be used to also classify species that were not yet known at the time when the system was created. The second advantage lies in the fact that, if there is actually, objectively a natural system of organisms, then its discovery should not be dependent on the subjective selection of traits and procedures of systematists. Systems created by individual systematists using various methods and employing various traits should gradually approach one another as knowledge is steadily accumulated and skills acquired. The third advantage of the natural system is its predictive potential. While an artificial system allows only description of the distribution of the traits on the basis of which the particular system was created, a natural system should also enable prediction of the distribution of those traits that were not used for classification of the organisms or that were not known at the time of creation of the system.