Division (biology)

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Division is a taxonomic rank in biological classification that is used differently in zoology and in botany.

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In botany and mycology, division refers to a rank equivalent to phylum. The use of either term is allowed under the International Code of Botanical Nomenclature, [1] and both are commonly used in scientific literature.

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 ecosystems, comprising 80% of vascular plant species. [2]

In zoology, the term division is applied to an optional rank subordinate to the infraclass and superordinate to the cohort. A widely used classification (e.g. Carroll 1988 [3] ) recognises teleost fishes as a Division Teleostei within Class Actinopterygii (the ray-finned fishes). Less commonly (as in Milner 1988 [4] ), living tetrapods are ranked as Divisions Amphibia and Amniota within the clade 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 eukaryotes, where heterotrophic organisms were classified under zoological nomenclature (using "phylum") while autotrophic organisms fell under botanical nomenclature (using "division"). Their proposal to standardise the terminology aimed to reflect the growing scientific appreciation for the unity of all organisms. 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. [5]

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. [6]

Taxonomic developments

The traditional term "division" in botanical and mycological taxonomy has been increasingly challenged by modern classification systems. 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 familiar ranks, notably using "phylum" rather than "division" at this level. This change aligns virus taxonomy more closely with zoological nomenclature and reflects a growing recognition that maintaining different terms (phylum vs. division) for equivalent ranks creates unnecessary complexity, particularly when classifying organisms like unicellular eukaryotes that may be treated under different codes depending on their nutritional mode. Under this system, the first viral realm established was Riboviria , encompassing all RNA viruses that encode an RNA-directed RNA polymerase. [7]

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 valid 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". [8]

Related Research Articles

<span class="mw-page-title-main">Linnaean taxonomy</span> Rank based classification system for organisms

Linnaean taxonomy can mean either of two related concepts:

  1. The particular form of biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his Systema Naturae (1735) and subsequent works. In the taxonomy of Linnaeus there are three kingdoms, divided into classes, and the classes divided into lower ranks in a hierarchical order.
  2. A term for rank-based classification of organisms, in general. That is, taxonomy in the traditional sense of the word: rank-based scientific classification. This term is especially used as opposed to cladistic systematics, which groups organisms into clades. It is attributed to Linnaeus, although he neither invented the concept of ranked classification nor gave it its present form. In fact, it does not have an exact present form, as "Linnaean taxonomy" as such does not really exist: it is a collective (abstracting) term for what actually are several separate fields, which use similar approaches.

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 and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a more inclusive group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum, class, order, family, genus, and species. The Swedish botanist Carl Linnaeus is regarded as the founder of the current system of taxonomy, as he developed a ranked system known as Linnaean taxonomy for categorizing organisms and binomial nomenclature for naming organisms.

<span class="mw-page-title-main">Genus</span> Taxonomic rank directly above species and directly below family

Genus is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

<span class="mw-page-title-main">Kingdom (biology)</span> Taxonomic rank

In biology, a kingdom is the second highest taxonomic rank, just below domain. Kingdoms are divided into smaller groups called phyla.

<span class="mw-page-title-main">Family (biology)</span> Taxonomic rank between genus and order

Family is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between order and genus. A family may be divided into subfamilies, which are intermediate ranks between the ranks of family and genus. The official family names are Latin in origin; however, popular names are often used: for example, walnut trees and hickory trees belong to the family Juglandaceae, but that family is commonly referred to as the "walnut family".

<span class="mw-page-title-main">Order (biology)</span> Taxonomic rank between class and family

Order is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. An immediately higher rank, superorder, is sometimes added directly above order, with suborder directly beneath order. An order can also be defined as a group of related families.

Virus classification is the process of naming viruses and placing them into a taxonomic system similar to the classification systems used for cellular organisms.

<span class="mw-page-title-main">Taxon</span> Grouping of biological populations

In biology, a taxon is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and given a particular ranking, especially if and when it is accepted or becomes established. It is very common, however, for taxonomists to remain at odds over what belongs to a taxon and the criteria used for inclusion, especially in the context of rank-based ("Linnaean") nomenclature. If a taxon is given a formal scientific name, its use is then governed by one of the nomenclature codes specifying which scientific name is correct for a particular grouping.

<span class="mw-page-title-main">Thermoproteota</span> Phylum of archaea

The Thermoproteota are prokaryotes that have been classified as a phylum of the domain Archaea. Initially, the Thermoproteota were thought to be sulfur-dependent extremophiles but recent studies have identified characteristic Thermoproteota environmental rRNA indicating the organisms may be the most abundant archaea in the marine environment. Originally, they were separated from the other archaea based on rRNA sequences; other physiological features, such as lack of histones, have supported this division, although some crenarchaea were found to have histones. Until 2005 all cultured Thermoproteota had been thermophilic or hyperthermophilic organisms, some of which have the ability to grow at up to 113 °C. These organisms stain Gram negative and are morphologically diverse, having rod, cocci, filamentous and oddly-shaped cells. Recent evidence shows that some members of the Thermoproteota are methanogens.

<span class="mw-page-title-main">Korarchaeota</span> Proposed phylum within the Archaea

The Korarchaeota is a proposed phylum within the Archaea. The name is derived from the Greek noun koros or kore, meaning young man or young woman, and the Greek adjective archaios which means ancient. They are also known as Xenarchaeota. The name is equivalent to Candidatus Korarchaeota, and they go by the name Xenarchaeota or Xenarchaea as well.

Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin mollis, and cutis. Individuals are very small, typically only 0.2–0.3 μm in size and have a very small genome size. They vary in form, although most have sterols that make the cell membrane somewhat more rigid. Many are able to move about through gliding, but members of the genus Spiroplasma are helical and move by twisting. The best-known genus in the Mollicutes is Mycoplasma. Colonies show the typical "fried-egg" appearance.

Nomenclature codes or codes of nomenclature are the various rulebooks that govern the naming of living organisms. Standardizing the scientific names of biological organisms allows researchers to discuss findings.

Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy.

<span class="mw-page-title-main">Taxonomic rank</span> Level in a taxonomic hierarchy

In biology, taxonomic rank is the relative or absolute level of a group of organisms in a hierarchy that reflects evolutionary relationships. Thus, the most inclusive clades have the highest ranks, whereas the least inclusive ones have the lowest ranks. Ranks can be either relative and be denoted by an indented taxonomy in which the level of indentation reflects the rank, or absolute, in which various terms, such as species, genus, family, order, class, phylum, kingdom, and domain designate rank. This page emphasizes absolute ranks and the rank-based codes require them. However, absolute ranks are not required in all nomenclatural systems for taxonomists; for instance, the PhyloCode, the code of phylogenetic nomenclature, does not require absolute ranks.

<span class="mw-page-title-main">Monera</span> Biological kingdom that contains unicellular organisms with a prokaryotic cell organization

Monera is historically a biological kingdom that is made up of prokaryotes. As such, it is composed of single-celled organisms that lack a nucleus.

<span class="mw-page-title-main">Phylum</span> High level taxonomic rank for organisms sharing a similar body plan

In biology, a phylum is a level of classification or taxonomic rank below kingdom and above class. Traditionally, in botany the term division has been used instead of phylum, although the International Code of Nomenclature for algae, fungi, and plants accepts the terms as equivalent. Depending on definitions, the animal kingdom Animalia contains about 31 phyla, the plant kingdom Plantae contains about 14 phyla, and the fungus kingdom Fungi contains about 8 phyla. Current research in phylogenetics is uncovering the relationships among phyla within larger clades like Ecdysozoa and Embryophyta.

<span class="mw-page-title-main">Bacterial phyla</span> Phyla or divisions of the domain Bacteria

Bacterial phyla constitute the major lineages of the domain Bacteria. While the exact definition of a bacterial phylum is debated, a popular definition is that a bacterial phylum is a monophyletic lineage of bacteria whose 16S rRNA genes share a pairwise sequence identity of ~75% or less with those of the members of other bacterial phyla.

<span class="mw-page-title-main">Bacterial taxonomy</span> Rank based classification of bacteria

Bacterial taxonomy is subfield of taxonomy devoted to the classification of bacteria specimens into taxonomic ranks.

There are several models of the Branching order of bacterial phyla, one of these was proposed in 1987 paper by Carl Woese.

<span class="mw-page-title-main">Glossary of scientific naming</span>

This is a list of terms and symbols used in scientific names for organisms, and in describing the names. For proper parts of the names themselves, see List of Latin and Greek words commonly used in systematic names. Note that many of the abbreviations are used with or without a stop.

References

  1. McNeill, J.; et al., eds. (2012). International Code of Nomenclature for algae, fungi, and plants (Melbourne Code), Adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011 (electronic ed.). International Association for Plant Taxonomy. Retrieved 2017-05-14.
  2. Judd, Walter S.; Campbell, Christopher S.; Kellogg, Elizabeth A.; Stevens, Peter F.; Donoghue, Michael J. (2002). Plant systematics, a phylogenetic approach (2nd ed.). Sunderland MA, USA: Sinauer Associates Inc. ISBN   0-87893-403-0.
  3. ( Carroll 1988 )
  4. ( Milner 1988 )
  5. Bold, H.C.; Cronquist, A.; Jeffey, C.; Johnson, L.A.S.; Marguilis, L.; Merximiller, H.; Takhtajan, A.L. (1978). "Proposa (10) to substitute the term phylum for division for groups treated as plants" (PDF). Taxon. 27 (1): 121–122.
  6. Woese, C.R.; Stackebrandt, E.; Macke, T.J.; Fox, G.E. (1985). "A phylogenetic definition of the major eubacterial taxa". Systematic and Applied Microbiology. 6 (2): 143–151. doi:10.1016/S0723-2020(85)80047-3.
  7. International Committee on Taxonomy of Viruses Executive Committee; Gorbalenya, Alexander E.; Krupovic, Mart; Mushegian, Arcady; Kropinski, Andrew M.; Siddell, Stuart G.; Varsani, Arvind; Adams, Michael J.; Davison, Andrew J.; Dutilh, Bas E.; Harrach, Balázs; Harrison, Robert L.; Junglen, Sandra; King, Andrew M. Q.; Knowles, Nick J.; Lefkowitz, Elliot J.; Nibert, Max L.; Rubino, Luisa; Sabanadzovic, Sead; Sanfaçon, Hélène; Simmonds, Peter; Walker, Peter J.; Zerbini, F. Murilo; Kuhn, Jens H. (2020). "The new scope of virus taxonomy: partitioning the virosphere into 15 hierarchical ranks". Nature Microbiology. 5 (5): 668–674. doi: 10.1038/s41564-020-0709-x . PMC   7186216 . PMID   32341570.
  8. Pallen, Mark J. (2024). "The dynamic history of prokaryotic phyla: discovery, diversity and division". International Journal of Systematic and Evolutionary Microbiology. 74 (9): e006508. doi:10.1099/ijsem.0.006508. PMC   11382960 . PMID   39250184.

Works cited