Scientific classification Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. Modern classification has its roots in the system of Carolus Linnaeus, who grouped species according to shared physical characteristics. These groupings have been revised since Linnaeus to improve consistency with the Darwinian principle of common descent. Molecular systematics, which uses genomic DNA analysis has driven many recent revisions and is likely to continue to do so. Scientific classification belongs to the science of taxonomy or biological systematics. Early systems The earliest known system of classifying forms of life comes from the Greek philosopher Aristotle, who classified animals based on their means of transportation (air, land, or water). In 1172 Ibn Rushd (Averroes) who was a judge (Qaadi) in Seville translated and abridged Aristotle's book "de Anima" (Animals). This book was translated into Latin by Mitchell the Scott. The next major advance in developing scientific classification was by the Swiss professor, Conrad Gessner (1516 - 1565). Gessner's work was a critical compilation of life known at the time. The exploration of parts of the New World next brought to hand descriptions and specimens of many novel forms of animal life. In the latter part of the 16th century and the beginning of the 17th careful study of animals commenced, which, directed first to familiar kinds, was gradually extended until it formed a sufficient body of knowledge to serve as an anatomical basis for classification. Advances in using this knowledge to classify living beings bears a debt to the research of medical anatomists, such as Fabricius (1537 - 1619), Petrus Severinus (1580 - 1656), William Harvey (1578 - 1657), and Tyson (1649 - 1708). Advances in classification due to the work of entomologists and the first microscopists is due to the research of people like Marcello Malpighi (1628 - 1694), Jan Swammerdam (1637 - 1680), and Robert Hooke (1635 - 1702). John Ray (1627 - 1705) was an English naturalist who published important works on plants, animals, and natural theology. His classification of plants in his Historia Plantarum was an important step towards modern taxonomy. Ray rejected the system of dichotomous division by which species were classified according to a pre-conceived, either/or type system, and instead classified plants according to similarities and differences that emerged from observation. Linnaean taxonomy Two years after John Ray's death Carolus Linnaeus (1707 - 1778) was born. His great work, the Systema Naturae, ran through twelve editions during his lifetime (1st ed. 1735). He is best known for his introduction of a method of modern classification; he created systematic zoology and botany in their present form. Linnaeus adopted Ray's conception of species, but he made the concept a practical reality by insisting that every species must have a unique Latin binomen, that is, a double name — the first half to be the name of the genus, common to several species, and the second half to be a single word, which is called the specific epithet. This convention is now referred to as binomial nomenclature, and the name 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 scientifically complete, an author label and publication details have to be added. Before Linnaeus, long many-worded names had been used, sometimes with one additional adjective, sometimes with another, so that no true names were fixed and accepted. Linnaeus' system made it easy to identify unambiguously any given species of plant or animal. He proceeded further to introduce into his system a series of groups: genus, order, class. The Linnaeus System works by placing each organism into a layered hierarchy of groups. Each group at a given layer is composed of a set of groups from the layer directly below. Simply knowing the two-part scientific name makes it possible to determine the other six layers. The groupings (taxa) of taxonomy from most general to most specific are: Kingdom Phylum (animals) or Division (plants) Class Order Family Genus Species Several acronym mnemonics have been made for these, for instance King Phillip came over for good soup, or Kings Play Chess On Funny Green Squares. Intermediate ranks may be created by adding prefixes, for instance: Superorder Order Suborder Infraorder Microorder Nanoorder etc. In addition, species are often subdivided into subspecies and other infraspecific categories (see subspecies, variety, subvariety and form). In certain circumstances prefixes beyond sub- need be used, normally micro-, nano-, etc., may be used. 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 genus and species. Modern developments The general approach Linnaeus took to classifying species and many of his taxonomic groups have remained standard in biology for at least two centuries. It is now generally accepted that classification should reflect the Darwinian principle of common descent, so that taxa include a single section of the evolutionary tree. Such groups are called monophyletic or paraphyletic. Since the 1960s a trend called cladistic taxonomy or cladism has emerged as a rival to more traditional phylogenetic classification. In this approach taxa are identified with clades, i.e. they can only be monophyletic. In these approaches, the ranking system in Linnaean taxonomy may be abandoned, and a new formal code of nomenclature, the Phylocode, is currently under development. Cladistic taxonomy remains controversial. Examples The usual classifications of three species follow: the Fruit Fly so familiar in genetics laboratories (Drosophila melanogaster), Humans, and the Sweetbay Magnolia. Fruit Fly (Drosophila melanogaster) 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 Related topics Binomial nomenclature Trinomial nomenclature Taxonomy International Code of Botanical Nomenclature International Code of Zoological Nomenclature List of biological orders List of Latin and Greek words commonly used in systematic names Phylogenetic tree Virus classification External links Phylocode - replacing older system with Cladistic system Classification of all living things, with many of pictures FAVORITE ARTICLES: History of the World    History of the United States    History of Europe    Ancient History    History    Military History    World War I    Bombing of Dresden    California    US Constitution    Frank Sinatra    Boston    Marbury v. 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