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Linnaeus, Carl

plants species system based

[li nay uhs], from 1762 Carl von Linné (1707–78) Swedish botanist: the great classifier of plants; popularized binomial nomenclature.

Linnaeus began his training in medicine at the University of Lund in 1727 but his father, a pastor and enthusiastic gardener, was unable to maintain his education. Linnaeus became interested in plants, and moved to the university at Uppsala with the help of a benefactor. Here he investigated the newly proposed theory that plants exhibit sexuality. O Rudbeck (1630–1702) (of Rudbeckia ) arranged that Linnaeus should take over his unwanted lectures on botany, and attendance rose from 80 to 400. He began to form a taxonomic system based on the plant sex organs, stamens and pistils. In 1732, Linnaeus undertook a visit to Lapland and in 1733–5 to mainland Europe, in order to examine its flora and animal life.

Deciding to earn his living as a physician (out of necessity), he went to Holland to qualify (1735). While there he published Systema naturae , in which he divided flowering plants into classes depending on their stamens and subdivided them into orders according to the number of their pistils. This system, though useful for ordering of the many new species being discovered, only partly showed the relationship between plants.

Linnaeus returned to Sweden as a practising physician in 1738, gaining patients in court circles. In 1741 he was appointed professor of medicine and botany at Uppsala and was able to extend his teaching, and his collection and investigation of plants. Linnaeus’s passion for classification led him to list the species and gather them into related groups (genera).

Linnaeus’s lasting service to taxonomy was his introduction in 1749 of binomial nomenclature; he gave each plant a latinesque generic noun followed by a specific adjective. This became the basis for modern nomenclature. Until that time plants had been given a name and short Latin description of their distinguishing features, unsatisfactory both as a name and description and leading to a tangled overgrowth, strangling further development. The Linnaean system helped pave the way towards notions of evolution, an idea Linnaeus rejected emphatically; he insisted no new species had been formed since Creation and that none had become extinct.

Linnaeus was an excellent teacher and his students travelled widely, imbued with his enthusiasm, in search of new forms of life; it is estimated that one in three died in the search.

Linnaeus had a complex, self-conscious personality. He had a tidy mind and absolute belief in the value of his system. He was skilful in getting others to accept his system, even though that meant setting aside much of their own work. He cleared the way for development in biology without taking part in it. The Linnaean system based on plant sexual organs was completely artificial, but convenient. By his success he stifled some aspects of botanical development for a century. After Linnaeus’s death his collection was bought by Sir James Smith (1759–1828). The London-based Linnean Society, founded by Smith in 1788, purchased the books and herbarium specimens in 1828.

Modern classification of living organisms has the species at the lowest level with (in order of increasing generality) the genus, family, order, class, phylum (for animals) division (for plants) and kingdom. Some of these categories may be further subdivided.

Thus modern man ( Homo sapiens sapiens ) belongs to the species Homo sapiens and subspecies sapiens ; his genus is Homo ; family Hominidae; order Primates; class Mammalia; phylum Chordata; kingdom Animalia.

Each category has its own definition: eg Primates, which includes gorillas, chimpanzees and humans, has defining features that include upright posture, opposable thumbs, large brain and similar blood plasma proteins. The family Hominidae includes modern man and fossil man species from the Pleistocene onwards.

After work on evolution it was natural to try and link classification with evolution. By the end of the 20th-c, classification could be based not only on morphology (i.e. form and structure) but also on genetic comparisons. These point to descent for all animals from an ancestor living over 600 million years ago; the fossil record begins 540 million years ago. From the common ancestor three lines of descent began the tree whose branches now include nearly all existing animal species.

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