Scientific classification

Scientific classification or biological classification is 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.

Examples

The usual classifications of five species follow: the fruit fly so familiar in genetics laboratories (Drosophila melanogaster), humans (Homo sapiens), the peas used by Gregor Mendel in his discovery of genetics (Pisum sativum), the fly agaric mushroom Amanita muscaria, and the bacterium Escherichia coli. The eight major ranks are given in bold; a selection of minor ranks are given as well.

Related Topics:
Fruit fly - Human - Pea - Gregor Mendel - Genetics - Fly agaric - Amanita muscaria - Escherichia coli

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Notes:

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• Botanists and mycologists use systematic naming conventions for higher taxa, using the Latin stem of the type genus for that taxon, plus a standard ending. (See below for a table of standard endings.) For example, the pea family Fabaceae is named after the stem "Fab-" of the type genus Faba plus the standard ending "-aceae" for a family (though to confuse matters, all plants in the genus Faba are now classified in Vicia, and the old name for the pea family, Leguminosae, is still widely used).
• Zoologists use similar conventions for higher taxa, but only up to the rank of superfamily.
• Higher taxa and especially intermediate taxa are prone to revision as new information about relationships is discovered. For example, the traditional classification of primates (class Mammalia ? subclass Theria ? infraclass Eutheria ? order Primates) is challenged by new classifications such as McKenna and Bell (class Mammalia ? subclass Theriformes ? infraclass Holotheria ? order Primates). See mammal classification for a discussion. These differences arise because there are only a small number of ranks available and a large number of branching points in the fossil record.
• Species may be further classified. Animals may be classified into subspecies (for example, Homo sapiens sapiens, modern humans). Plants may be classified into subspecies (for example, Pisum sativum subsp. sativum, the garden pea) or varieties (for example, Pisum sativum subsp. sativum var. macrocarpon, snow pea), with commercial "races" being called cultivars (for example, Pisum sativum sativum var. macrocarpon 'Snowbird', the common snow pea cultivar 'Snowbird'). Bacteria may be classified by strains (for example , a strain that can cause food poisoning).