Division is a

taxonomic rank In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of or ...

biological classification In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are give ...

that is used differently in zoology and in botany. In

botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

and mycology, ''division'' is the traditional name for a rank now considered equivalent to phylum. The use of either term is allowed under the International Code of Botanical Nomenclature. The main Divisions of land plants are the Marchantiophyta (liverworts), Anthocerotophyta (hornworts), Bryophyta (mosses), Filicophyta (ferns), Sphenophyta (horsetails), Cycadophyta (cycads), Ginkgophyta (ginkgo)s, Pinophyta (conifers), Gnetophyta (gnetophytes), and the Magnoliophyta (Angiosperms, flowering plants). The Magnoliophyta now dominate terrestrial

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

s, comprising 80% of vascular plant species. In

zoology Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...

, the term ''division'' is applied to an optional rank subordinate to the infraclass and superordinate to the legion and cohort. A widely used classification (e.g. Carroll 1988) recognises teleost fishes as a Division Teleostei within Class

Actinopterygii Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class (biology), class of Osteichthyes, bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built ...

(the ray-finned fishes). Less commonly (as in Milner 1988), living tetrapods are ranked as Divisions Amphibia and Amniota within the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

of vertebrates with fleshy limbs ( Sarcopterygii).

Proposals for standardisation

In 1978, a group of botanists including Harold Charles Bold, Arthur Cronquist and Lynn Margulis proposed replacing the term "division" with "phylum" in botanical nomenclature, arguing that maintaining different terms for the same taxonomic rank across biological kingdoms created unnecessary confusion. This was particularly problematic for unicellular

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s, where heterotrophic organisms were classified under zoological nomenclature (using "phylum") while autotrophic organisms fell under botanical nomenclature (using "division"). They proposed updating the International Code of Botanical Nomenclature to use "phylum" and "subphylum" throughout, while maintaining that names originally published as divisions would be treated as if they had been published as phyla.

Molecular phylogenetic classification

The use of molecular methods, particularly 16S ribosomal RNA analysis, helped establish major bacterial divisions in the 1980s. In 1985, Carl Woese and colleagues identified ten major groups of eubacteria through oligonucleotide signature analysis, noting that these groupings were "appropriately termed eubacterial Phyla or Divisions." This work provided early molecular evidence for the equivalence of bacterial divisions with phyla and helped establish a phylogenetic basis for high-level bacterial classification.

Viruses and prokaryotes

In 2020, the International Committee on Taxonomy of Viruses (ICTV) formalised a 15-rank hierarchical classification system, ranging from the highest rank " realm" (rather than domain) down through the lower ranks, notably using "phylum" rather than "division". Under this system, the first viral realm established was '' Riboviria'', encompassing all

RNA virus An RNA virus is a virus characterized by a ribonucleic acid (RNA) based genome. The genome can be single-stranded RNA (ssRNA) or double-stranded (Double-stranded RNA, dsRNA). Notable human diseases caused by RNA viruses include influenza, SARS, ...

es that encode an RNA-directed RNA polymerase. In 2021, the International Code of Nomenclature of Prokaryotes (ICNP) formally included the rank of phylum for the first time, adopting the suffix "-ota" for phylum names. This led to the publication of names for 46 prokaryotic phyla with cultured representatives, replacing some established names with neologisms – for example, " Proteobacteria" became " Pseudomonadota" and " Firmicutes" became "

Bacillota The Bacillota (synonym Firmicutes) are a phylum of bacteria, most of which have Gram-positive cell wall structure. They have round cells, called cocci (singular coccus), or rod-like forms (bacillus). A few Bacillota, such as '' Megasphaera'', ...

References

Works cited

* * {{Taxonomic ranks Scientific classification Botanical nomenclature