Class (biology)

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For other uses, see Class (disambiguation). Class (biology)_sentence_0

This page is about the taxonomic grouping of related organisms; it should not be confused with the ecological grouping of unrelated plant taxa in phytosociology. Class (biology)_sentence_1

In biological classification, class (Latin: classis) is a “taxonomic rank”, as well as a taxonomic unit, a taxon, in that rank. Class (biology)_sentence_2

Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order. Class (biology)_sentence_3

Definition Class (biology)_section_0

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 French botanist Joseph Pitton de Tournefort in his classification of plants that appeared in his Eléments de botanique, 1694. Class (biology)_sentence_4

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. Class (biology)_sentence_5

This said, the composition of each class is ultimately determined by the subjective judgement of taxonomists. Class (biology)_sentence_6

Often there is no exact agreement, with different taxonomists taking different positions. Class (biology)_sentence_7

There are no objective rules for describing a class, but for well-known animals there is likely to be consensus. Class (biology)_sentence_8

In the first edition of his Systema Naturae (1735). Class (biology)_sentence_9

Carl Linnaeus divided all three of his kingdoms of Nature (minerals, plants, and animals) into classes. Class (biology)_sentence_10

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. Class (biology)_sentence_11

In botany, classes are now rarely discussed. Class (biology)_sentence_12

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. Class (biology)_sentence_13

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. Class (biology)_sentence_14

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 the early nineteenth century. Class (biology)_sentence_15

Hierarchy of ranks below and above the level of class Class (biology)_section_1

As with the other principal ranks, Classes can be grouped and subdivided. Class (biology)_sentence_16

Here are some examples. Class (biology)_sentence_17

Class (biology)_table_general_0

NameClass (biology)_header_cell_0_0_0 Meaning of prefixClass (biology)_header_cell_0_0_1 Example 1Class (biology)_header_cell_0_0_2 Example 2Class (biology)_header_cell_0_0_3 Example 3Class (biology)_header_cell_0_0_4 Example 4Class (biology)_header_cell_0_0_5
SuperclassClass (biology)_cell_0_1_0 : aboveClass (biology)_cell_0_1_1 TetrapodaClass (biology)_cell_0_1_2 Class (biology)_cell_0_1_3 TetrapodaClass (biology)_cell_0_1_4 Class (biology)_cell_0_1_5
ClassClass (biology)_cell_0_2_0 Class (biology)_cell_0_2_1 MammaliaClass (biology)_cell_0_2_2 MaxillopodaClass (biology)_cell_0_2_3 AvesClass (biology)_cell_0_2_4 DiplopodaClass (biology)_cell_0_2_5
SubclassClass (biology)_cell_0_3_0 : underClass (biology)_cell_0_3_1 TheriaClass (biology)_cell_0_3_2 ThecostracaClass (biology)_cell_0_3_3 Class (biology)_cell_0_3_4 ChilognathaClass (biology)_cell_0_3_5
InfraclassClass (biology)_cell_0_4_0 : belowClass (biology)_cell_0_4_1 Class (biology)_cell_0_4_2 CirripediaClass (biology)_cell_0_4_3 NeognathaeClass (biology)_cell_0_4_4 HelminthomorphaClass (biology)_cell_0_4_5
SubterclassClass (biology)_cell_0_5_0 : below, underneathClass (biology)_cell_0_5_1 Class (biology)_cell_0_5_2 Class (biology)_cell_0_5_3 Class (biology)_cell_0_5_4 ColobognathaClass (biology)_cell_0_5_5
ParvclassClass (biology)_cell_0_6_0 : small, unimportantClass (biology)_cell_0_6_1 Class (biology)_cell_0_6_2 Class (biology)_cell_0_6_3 NeornithesClass (biology)_cell_0_6_4 -Class (biology)_cell_0_6_5

See also Class (biology)_section_2

Class (biology)_unordered_list_0

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: (biology).