Class (biology)
In
History
The class as a distinct rank of biological classification having its own distinctive name (and not just called a top-level genus (genus summum)) was first introduced by the
Insofar as a general definition of a class is available, it has historically been conceived as embracing taxa that combine a distinct grade of organization—i.e. a 'level of complexity', measured in terms of how differentiated their organ systems are into distinct regions or sub-organs—with a distinct type of construction, which is to say a particular layout of organ systems.
In the first edition of his Systema Naturae (1735),[3] Carl Linnaeus divided all three of his kingdoms of nature (minerals, plants, and animals) into classes. Only in the animal kingdom are Linnaeus's classes similar to the classes used today; his classes and orders of plants were never intended to represent natural groups, but rather to provide a convenient "artificial key" according to his Systema Sexuale, largely based on the arrangement of flowers. In botany, classes are now rarely discussed. Since the first publication of the APG system in 1998, which proposed a taxonomy of the flowering plants up to the level of orders, many sources have preferred to treat ranks higher than orders as informal clades. Where formal ranks have been assigned, the ranks have been reduced to a very much lower level, e.g. class Equisitopsida for the land plants, with the major divisions within the class assigned to subclasses and superorders.[4]
The class was considered the highest level of the taxonomic hierarchy until
were introduced in the early nineteenth century.Subdivisions
As with the other principal ranks, classes can be grouped and subdivided.[b]
Name | Meaning of prefix | Example 1 | Example 2 | Example 3[6] | Example 4 |
---|---|---|---|---|---|
Superclass | super: above | Tetrapoda |
|||
Class | Mammalia |
Maxillopoda |
Sauropsida | Diplopoda
| |
Subclass | sub: under | Theria | Thecostraca | Avialae | Chilognatha |
Infraclass | infra: below | Cirripedia |
Aves | Helminthomorpha
| |
Subterclass | subter: below, underneath | Colobognatha | |||
Parvclass | parvus: small, unimportant | Neornithes |
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|
See also
Explanatory notes
References
- ^ "Class". Biology Articles, Tutorials & Dictionary Online. 23 July 2021.
- .
- ISBN 0-674-36446-5
- ^ Collins, A.G., Valentine, J.W. (2001). "Defining phyla: evolutionary pathways to metazoan body plans" Archived 2020-04-27 at the Wayback Machine. Evol. Dev. 3: 432–442.
- ^ Classification according to Systema Naturae 2000, which conflicts with Wikipedia's classification. "The Taxonomicon: Neornithes". Retrieved 3 December 2010.