In biological classification , class ( Latin : classis ) is a taxonomic rank , as well as a taxonomic unit, a taxon , in that rank. It is a group of related taxonomic orders. Other well-known ranks in descending order of size are life , domain , kingdom , phylum , order , family , genus , and species , with class ranking between phylum and order.
5-420: Ranunculidae is a subclass of plants used in some taxonomic systems and not others. By necessity it includes the order Ranunculales , but otherwise it differs between taxonomic systems. This Ranunculales article is a stub . You can help Misplaced Pages by expanding it . Class (biology) The class as a distinct rank of biological classification having its own distinctive name – and not just called
10-495: A top-level genus (genus summum) – was first introduced by French botanist Joseph Pitton de Tournefort in the classification of plants that appeared in his Eléments de botanique of 1694. 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
15-434: A distinct type of construction, which is to say a particular layout of organ systems. This said, the composition of each class is ultimately determined by the subjective judgment of taxonomists . In the first edition of his Systema Naturae (1735), 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
20-450: 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
25-503: 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. The class was considered the highest level of the taxonomic hierarchy until George Cuvier 's embranchements , first called Phyla by Ernst Haeckel , were introduced in
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