Approaches to Taxonomic Classification (Excerpts from pgs. 1-2)
Classification in Zoology:
a An ending recommended but not mandatory
according to the International Code of Zoological
b An ending customary but not cited in the
No phylum is totally immune to an occasional reshuffling of species, renaming of constituent taxa, and recalculation of total species richness (number of species). This dynamic feature of the discipline is, in part, a necessary response to the acquisition of new knowledge, but it also results from the ubiquitous and almost inherant disagreements that usually typify groups of two or more scientists. Taxonomists are frequently labeled "splitters" or "lumpers" according to whether, respectively, they tend to acknowledge more or fewer species within an assemblage. Classifications they produce based on diverse scientific approaches, such as cladistics and numerical (=phenetics) taxonomy, can produce dramatically different views of relationships among taxa. Moreover, molecular systematics has sometimes shaken the traditional taxonomic schemes based on classical phenotype characters.
Although arguments at the species level are especially rampant, debates occasionally break out regarding the categorization of higher tiers, including classes and phyla.
Species are named today using a system of binominal nomenclature (= names composed of two parts) based on the 18th century proposal of the brilliant Swedish naturalist Carl von Linné (or Carolus Linnaeus, the latinized form he preferred to use). This is the "genus and species" designation familiar to most biology students (e.g., Homo Sapiens for the human species.) You will occasionally see a species designated with three names (a trinomen), which is permissible under guidelines of the International Code of Zoological Nomenclature. For example, Bosmina (Sinobosmina) freyi is the genus, subgenus, and species name of a water flea, or cladoceran, common in rivers (it is one of a species complex formerly called Bosmina longirostris). In contrast, Pheidole xerophila tucsonica is the genus, species, and subspecies name of a harvester ant living in the desert near Tucson, Arizona. Scientific names are either in Latin or in a form that has been latinized (e.g., B.(S.) freyi was formed by latinizing the last name of Dr. David G. Frey, to honor this now-deceased co-author of Chapter 21).
The final arbiter for naming taxa according to this system is the International Commission on Zoological Nomenclature, a judicial body elected periodically by the International Congress of Zoology to evaluate taxonomic names proposed by scientists.
Source: Ecology and Classification of North American Freshwater Invertebrates, Excerpts from Introduction, Pages 1-3
Thorp and Covich, Academic Press, 2001