Scientific classification

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'''Scientific classification''' refers to how biologistsgroup and categorize extinct and living species of organisms.Modern classification has its roots in the system of CarolusLinnaeus, who grouped species according to shared physicalcharacteristics. These groupings have been revised since Linnaeus toimprove consistency with the Darwinian principle ofcommon descent. Molecular systematics, which usesgenomic DNA analysis has driven manyrecent revisions and is likely to continue to do so. Scientificclassification belongs to the science of taxonomy orbiological systematics.== Early systems ==The earliest known system of classifying forms of life comes from theGreek philosopher Aristotle, who classified animals based on theirmeans of transportation (air, land, or water).In 1172 Ibn Rushd (Averroes) who was a judge (Qaadi) in Sevilletranslated and abridged Aristotle's book "de Anima" (Animals). Thisbook was translated into Latin by Mitchell the Scott.The next major advance in developing scientific classification was bythe Swiss professor, Conrad Gessner (1516 - 1565). Gessner's workwas a critical compilation of life known at the time.The exploration of parts of the New World next brought to handdescriptions and specimens of many novel forms of animal life. In thelatter part of the 16th century and the beginning of the 17th carefulstudy of animals commenced, which, directed first to familiar kinds,was gradually extended until it formed a sufficient body of knowledgeto serve as an anatomical basis for classification. Advances in usingthis knowledge to classify living beings bears a debt to the researchof medical anatomists, such as Fabricius (1537- 1619), Petrus Severinus (1580 - 1656), William Harvey (1578 -1657), and Tyson (1649 - 1708). Advances in classification due to thework of entomologists and the first microscopists is due to theresearch of people like Marcello Malpighi (1628 - 1694), JanSwammerdam (1637 - 1680), and Robert Hooke (1635 - 1702). JohnRay (1627 - 1705) was an English naturalist who published importantworks on plants, animals, and natural theology. His classification ofplants in his Historia Plantarum was an important step towardsmodern taxonomy. Ray rejected the system of dichotomous division bywhich species were classified according to a pre-conceived, either/ortype system, and instead classified plants according to similaritiesand differences that emerged from observation.== Linnaean taxonomy ==Two years after John Ray's death Carolus Linnaeus (1707 - 1778) wasborn. His great work, the ''Systema Naturae'', ran through twelveeditions during his lifetime (1st ed. 1735). He is best known for hisintroduction of a method of modern classification; he createdsystematic zoology and botany in their present form.Linnaeus adopted Ray's conception of species, but he made the concept apractical reality by insisting that every species must have a uniqueLatin binomen, that is, a double name — the first half to be thename of the genus, common to several species, and the second half to bea single word, which is called the ''specific epithet''. Thisconvention is now referred to as binomial nomenclature, and thename formed from the two parts is known as the scientific name or"systematic name" of a species. When a species is further subdivided,the trinomial nomenclature is used. For a name to be scientificallycomplete, an author label and publication details have to be added.Before Linnaeus, long many-worded names had been used, sometimes withone additional adjective, sometimes with another, so that no true nameswere fixed and accepted. Linnaeus' system made it easy to identifyunambiguously any given species of plant or animal. He proceededfurther to introduce into his system a series of groups: genus, order,class.The Linnaeus System works by placing eachorganism into a layered hierarchy of groups. Each group at a givenlayer is composed of a set of groups from the layer directly below.Simply knowing the two-part scientific name makes it possible todetermine the other six layers.The groupings (taxa) of taxonomy from most general to mostspecific are:*Kingdom*Phylum (animals) or Division (plants)*Class*Order*Family*Genus*SpeciesSeveral acronym mnemonics have been made for these, for instance'''K'''ing '''P'''hillip '''c'''ame '''o'''ver '''f'''or '''g'''ood'''s'''oup, or '''K'''ings '''P'''lay '''C'''hess '''O'''n '''F'''unny'''G'''reen '''S'''quares.Intermediate ranks may be created by adding prefixes, for instance:*''Super''order*Order*''Sub''order*''Infra''order*''Micro''order*''Nano''order*etc.In addition, species are often subdivided into subspecies and otherinfraspecific categories (see subspecies,variety, subvariety and form). In certain circumstances prefixes beyond''sub''- need be used, normally ''micro''-, ''nano''-, etc., may beused. Some other ranks are also sometimes added. For instance, domains or empires may be given above the level of kingdom,tribes between the levels of family and genus, and sections and series between the genusand species.

== Modern developments ==

The general approach Linnaeus took toclassifying species and many ofhistaxonomic groups have remainedstandard in biology for at leasttwocenturies. It is now generallyaccepted that classificationshouldreflect the Darwinian principle ofcommon descent, so thattaxainclude a single section of theevolutionary tree. Such groupsarecalled monophyletic orparaphyletic.Since the 1960s a trendcalled cladistic taxonomyor cladism hasemerged as a rival to moretraditional phylogeneticclassification. Inthis approach taxa areidentified with clades, i.e.they can only bemonophyletic. In theseapproaches, the ranking systemin Linnaeantaxonomy may be abandoned, anda new formal code ofnomenclature, thePhylocode, is currently underdevelopment.Cladistic taxonomyremains controversial.== Examples ==Theusualclassifications of three species follow: the Fruit Fly sofamiliaringenetics laboratories (''Drosophila melanogaster''),Humans, andtheSweetbay Magnolia.

=== Fruit Fly (''Drosophilamelanogaster'')===

'''Kingdom'''	Animalia
'''Phylum'''	Arthropoda
'''Class'''	Insecta
'''Order'''	Diptera
'''Family'''	Drosophilidae
'''Genus'''	''Drosophila''
'''Species'''	''melanogaster''

=== Human (''Homo sapiens'') ===

'''Kingdom'''	Animalia
'''Phylum'''	Chordata
'''Subphylum'''	Vertebrata
'''Class'''	Mammalia
'''Subclass'''	Eutheria
'''Order'''	Primates
'''Suborder'''	Haplorhini
'''Family'''	Hominidae
'''Genus'''	''Homo''
'''Species'''	''sapiens''

=== Sweetbay Magnolia (''Magnolia virginiana'') ===

'''Kingdom'''	Plantae
'''Division'''	Magnoliophyta
'''Class'''	Magnoliopsida
'''Order'''	Magnoliales
'''Family'''	Magnoliaceae
'''Genus'''	''Magnolia''
'''Species'''	''virginiana''

Note in this last example, that most of the taxa are named after the type genus, ''Magnolia''. Sweetbay magnolia is the first species of the genus named, and is the type species of the genus ''Magnolia'', and thus also of all flowering plants. == Group suffixes == Taxa above the genus level are often given names derived from the type genus. The suffixes used to form these names depend on the kingdom, and sometimes the phylum and class, as follows:

Taxon	Plants	Algae	Fungi	Animals
Division/Phylum	-phyta	-phyta	-mycota
Subdivision/Subphylum	-phytina	-phytina	-mycotina
Class	-opsida	-phyceae	-mycetes
Subclass	-idae	-phycidae	-mycetidae
Order	-ales	-ales	-ales
Suborder	-ineae	-ineae	-ineae
Superfamily	-acea	-acea	-acea	-oidea
Family	-aceae	-aceae	-aceae	-idae
Subfamily	-oideae	-oideae	-oideae	-inae
Tribe	-eae	-eae	-eae	-ini
Subtribe	-inae	-inae	-inae	-ina