In biological classification, the order is
a taxonomic rank used in the classification of organisms and
recognized by the nomenclature codes. Other well-known ranks are life, domain,
kingdom, phylum, class, family, genus, and species, with order fitting in
between class and family. An immediately higher rank, superorder, may be added
directly above order, while suborder would be a lower rank.
a taxonomic unit, a taxon, in that rank. In that case the plural is orders.
Example: The Juglans and Hickory trees belong to the family Juglandaceae, which
is placed in the order Fagales. What does and does not belong to each
order is determined by a taxonomist. Similarly for the question if a
particular order should be recognized at all. Often there is no exact agreement,
with different taxonomists each taking a different position. There are no hard
rules that a taxonomist needs to follow in describing or recognizing an order.
Some taxa are accepted almost universally, while others are recognised
only rarely. For some groups of organisms, consistent
suffixes are used to denote that the rank is an order. The Latin suffix
-(i)formes meaning "having the form of" is used for the scientific name of
orders of birds and fishes, but not for those of mammals and invertebrates. The
suffix -ales is for the name of orders of vascular plants.
Hierarchy of ranks For some clades covered by the
International Code of Zoological Nomenclature, a number of additional
classifications are sometimes used, although not all of these are officially
recognised. In their 1997 classification of mammals,
McKenna and Bell used two extra levels between Superorder and Order:
"Grandorder" and "Mirorder". Michael Novacek inserted them at the same
position. Michael Benton inserted them between superorder and magnorder
instead. This position was adopted by Systema Naturae 2000 and others.
In botany, the ranks of subclass and suborder are secondary ranks pre-defined
as respectively above and below the rank of order. Any number of further ranks
can be used as long as they are clearly defined.
History of the concept The order as a distinct rank of
biological classification having its own distinctive name) was first introduced
by the German botanist Augustus Quirinus Rivinus in his classification of plants
that appeared in a series of treatises in the 1690s. Carolus Linnaeus was the
first to apply it consistently to the division of all three kingdoms of nature
in his Systema Naturae. = Botany =
For plants, Linnaeus' orders in the Systema Naturae and the Species
Plantarum were strictly artificial, introduced to subdivide the artificial
classes into more comprehensible smaller groups. When the word ordo was first
consistently used for natural units of plants, in 19th century works such as
the Prodromus of de Candolle and the Genera Plantarum of Bentham & Hooker, it
indicated taxa that are now given the rank of family.
In French botanical publications, from Michel Adanson's Familles naturelles des
plantes and until the end of the 19th century, the word famille was used as a
French equivalent for this Latin ordo. This equivalence was explicitly stated
in the Alphonse De Candolle's Lois de la nomenclature botanique, the precursor of
the currently used International Code of Nomenclature for algae, fungi, and
plants. In the first international Rules of
botanical nomenclature from the International Botanical Congress of
1905, the word family was assigned to the rank indicated by the French
"famille", while order was reserved for a higher rank, for what in the 19th
century had often been named a cohors. Some of the plant families still retain
the names of Linnaean "natural orders" or even the names of pre-Linnaean
natural groups recognised by Linnaeus as orders in his natural classification.
Such names are known as descriptive family names.
= Zoology = In zoology, the Linnaean orders were
used more consistently. That is, the orders in the zoology part of the
Systema Naturae refer to natural groups. Some of his ordinal names are still in
use. See also
Biological classification Cladistics
Phylogenetics Rank
Rank Systematics
Taxonomy Virus classification
References