Phylum

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The term root has been used in biological systematics at two different levels. On the one hand called trunk or phylum a hierarchical rank, ie a taxonomic unit, near the root of the system, the exact classification varies depending on the subject area. On the other hand, various lineages within a species of bacteria, archaea and also in viruses are referred to as strains. in the latter case it is not a taxonomic rank.

Eukaryotes

In the domain of eukaryotes ( Eukarya ) it lies between rich and class. Every organism described to be associated with a strain, ie the strain belongs to the categorical ranks. It is sometimes further divided into sub- tribes ( Subphyla, singular: subphylum ). Several strains are summarized in some cases to an over strain ( Superphylum or home group ). Homo sapiens as an example is part of the tribe of chordates, where the subphylum of vertebrates.

Botany

In botany and mycology addition to the parent and the department synonym ( divisio ) is allowed. The name suffix is standardized in botany and mycology, the names end in botany on - phytase, in mycology on - mycota. Traditionally, nine strains of algae, eight of the higher plants ( Embryophyta ) and four fungi are differentiated, this classification is outdated according to recent findings to a large extent, but is used often on.

Zoology

The founder of modern taxonomy, Carl Linnaeus, divided the animal kingdom ( regnum Animalia ) in class ( classis ), orders ( ordo ), genera ( genus) and species ( species). The French anatomist and naturalist Georges Cuvier named the top-ranked departments that correspond to about Linnaeus " classes ", " embranchements " (with him four: Vertebres, Mollusks, articulés, zoophytes ), including follow only the "classes ". The term "tribe" ( phylum ) as the basic units and its name was first introduced by the German zoologist Ernst Haeckel. Haeckel called 5 strains: coelenterates, echinoderms, Articulaten, molluscs, vertebrates ( the sponges, " Spongiae " were known by him, but not the animal kingdom, but the protists attributed ). For Haeckel tribes were fundamentally different organization types that can each be traced back to a common ancestral stock them. Due to the advances in knowledge in zoology are currently about thirty tribes distinguished (cf. Nomenclature of multicellular animals ), the number depending on the scientific opinion but something different. More difficult is the classification of " single-celled " or " protists ". Traditionally regarded as a single trunk, it strains are currently divided into a number. For example, different Thomas Cavalier- Smith 18 tribes.

In science are currently side by side two classification schemes in use. In addition to the classical, going back to Linnaeus systematic, organized hierarchically, is founded by Willi Hennig phylogenetic systematics or " cladistics " resigned. In the phylogenetic system, all units should be based on community of descent, and all descendants of a common ancestral species include ( " holophyletic " units). Through the successive splittings results in a tree structure. Groupings that also go back to a common ancestral species (ie " monophyletic " are ), but do not include all their descendants are called by him " paraphyletic ". Paraphyletic units are in classical systematics, but not allowed in the phylogenetic systematics. Through this reform, the issue of joint shape and organization, which was based on the classic concept of a phylum, receded into the background. Most of the morphologically justified strains proved true as holophyletisch. But: The common plan is for this system for the systematic classification not more fundamentally, appropriately defined units must be abandoned if they are not holophyletisch, even if the so combined taxa were easily recognizable as belonging together by their common plan.

In general, the classical animal strains in the phylogenetic system as organizational units usually operated but they no longer, as in the classical system a specific, defined rank, so do not even necessarily have to be equal. If it can be demonstrated that a group of species, which has hitherto been regarded as a tribe, a subgroup of another -conceived as the root taxon forms, but is usually ceased to refer to them as a tribe. A more recent example, the beard worms (formerly ordinary Pogonophora now: family Siboglinidae the root Annelida, or segmented worms ).

Strain as a taxonomic unit in prokaryotes

In the domains Bacteria ( Bacteria) and Archaea ( Archaea) is the rank of master ( Phylum ) directly under the domain, these two domains are divided into tribes so ( phyla ). The number of stems is controversial in the river and within science; in recent years, their number has considerably increased. Currently, it is assumed that at least 35 strains of bacteria and 18 strains of archaea.

As a regular or phylum is currently usually a group of organisms grouped with similar shapes and similar " blueprint", if this so dissimilar to that of members of other tribes is that they can not both be merged on a common basic pattern them. The present-day tribes can be traced back to the Cambrian, with few exceptions based on fossil finds.

Taxa in the rank of a tribe (or any other above the superfamily ) are not subject to the rules of the ICZN. This means that the principles set out in the Code rules, in particular those concerning the validity ( availability) of names and the principle of priority ( which states that if multiple names for the same Grupe are available, each of which first proposed / oldest name to be used ) to the names of the strains do not have to be applied. Names of strains are therefore more or less codified by the consensus of the professionals involved that use a specific name - or not. In practice, most scientists are well aware also among the tribes, the priority and use the traditional names even if they redefine the taxa involved in something, such as broken out taxa from them or add others. Deviations occur mainly at supporters of the PhyloCode. This newly proposed rules but is ignored by most scientists.

Strains within a prokaryotic species and in viruses

No taxonomic rank are as tribes (English: strains ) designated lineages of bacteria, archaea and viruses. This culture strains ( pure culture ) are used among other things as nomenclatural type for definition of species and subspecies as well as in biotechnology. A tribe in this sense consists of a clone, since it is a produced by asexual population.