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Tuesday, October 2, 2012

Carl Linnaeus

 

The Swedish naturalist Carl Linnaeus (1707-1778) established the binomial system of biological nomenclature, formalized biological classification, and gave the first organization to ecology.
Carl Linnaeus was born on May 23, 1707, in Råshult, the eldest of five children. Two years after his birth his father became the Lutheran minister at Stenbrohult. There young Carl had his own garden, which, he later remarked, "inflamed my soul with an unquenchable love of plants."
In 1716 Linnaeus went to the grammar school in nearby Växjö. He studied Latin, religion, mathematics, and science, but his interest in plants tended to interfere with his studies. A favorite book was Aristotle's Historia animalium, which his father had given him. His mother hoped he would enter the ministry, but he showed no interest in that career. Johan Rothman, a master at the high school, encouraged Linnaeus's interests in science and suggested that he study medicine. The father reluctantly agreed, and Rothman tutored Linnaeus in physiology and botany for a year.
In 1727 Linnaeus entered the University of Lund. The science and medical instruction was very weak, and after a year he transferred to Uppsala University, where he found that the two medical professors were old and seldom lectured. Fortunately, he soon attracted the interest of Olof Celsius, a theology professor who was interested in the plants of Sweden. Celsius gave him free room and board and became his mentor.
The most important contemporary development in botany was the study of the sexuality of plants. Linnaeus had learned of this discovery while at Växjö, but it was not generally known in Sweden. He wrote an essay on the subject, which Celsius showed to one of the professors of medicine, Olof Rudbeck. Rudbeck was so impressed with Linnaeus that he appointed him lecturer in botany and tutor of his sons.
His Travels
In 1732 Linnaeus received a grant from the Uppsala Scientific Society for a trip to Lapland. In 5 months he gained valuable knowledge of the Lapps and the natural resources of the country. The success of this trip led to invitations from the government at various times to make other trips to survey the resources of Sweden. On one of his journeys, through the province of Dalarna in 1734, he met Sara Lisa Moraea, to whom he became engaged.
Linnaeus needed a medical degree to become professionally established. At some European universities it could be earned by satisfactorily completing examinations and defending a thesis. In 1735 Linnaeus traveled to Holland, and after a week at the University of Harderwijk he took the examinations, defended his thesis on the cause of intermittent fever, and received his degree. He remained away from Sweden for 3 years, spending most of his time in Holland but also traveling in Germany, France, and England, meeting leading scientists as he went. He had brought with him a number of botanical manuscripts, and these won the admiration of the leading naturalists and the wealthy banker George Clifford.
These men provided Linnaeus with work and assisted in the publication of his manuscripts. The years in Holland were the most productive of his life: he published his Systema naturae, Bibliotheca botanica, Fundamenta botanica, Critica botanica, Flora Lapponica, Methodus sexualis, Genera plantarum, Classes plantarum, Hortus Cliffortianus, and lesser works. With understandable pride he concluded that in 3 years he had "written more, discovered more, and made a greater reform in botany than anybody before had done in an entire lifetime."
The Professor
Linnaeus returned to practice medicine in Stockholm. He was appointed physician to the Admiralty and soon had the best medical practice in Stockholm. In 1739 he married Sara Moraea; they had two sons and four daughters. Linnaeus became professor of botany at Uppsala University in 1741.
As a professor, Linnaeus was immensely successful. He had a genius for organization which he applied to both science and science education. His popularity with students was also based upon his attractive personality and his concern for their success. He taught botany, zoology, natural history, pharmacy, dietetics, and mineralogy. There were 186 students who defended these under his supervision. It was the custom for the adviser to write much, if not all, of the dissertation, and those which his students defended contained some of his important ideas in ecology and natural history. These theses were published separately and then collected into a periodical entitled Amoenitates academicae (1749-1790).
Linnaeus was not without detractors, some sincere, but many merely jealous. However, the love of his students and the value of his work ensured both his widespread influence and the receipt of many honors. He was appointed chief royal physician in 1747 and was knighted in 1758; he then took the name Carl von Linné. He retired in 1776 and was permitted to appoint as his successor his son Carl. Linnaeus died in Uppsala on Jan. 10, 1778.
Binomial Nomenclature and Classification
Linnaeus is most widely known for having introduced efficient procedures for naming and classifying plants and animals at a time when new species were being rapidly discovered by explorers. Before the insights of evolutionary theory provided a rationale for classification and nomenclature, the criteria used were arbitrarily chosen according to similarities in morphology, habitat, and man's uses of the species. In Linnaeus's day the problems of classification were most acutely felt in relation to flowering plants. Naturalists agreed that morphology was the most natural criterion, but in practice it was difficult to know which groups were most similar.
Linnaeus realized that new plants were being discovered faster than their morphological relationships could be established, and he decided to abandon for a while the attempt to achieve a natural classification. He devised a simple numerical classification based upon the number of floral parts. This system was so useful that it remained popular into the 19th century.
Gradually Linnaeus also developed a consistent system of names, in which each species of plant and animal had a genus name followed by a specific name: for example, Plantago virginica and Plantago lanceolata were the names of two species of plantain. Because he was the first to achieve a consistent and efficient system of nomenclature, botanists agreed in 1905 to accept his Species plantarum (2 vols., 1753) and zoologists agreed to accept the tenth edition of his Systema naturae (1758) as the official starting points for scientific names of plants and animals.
Ecology as the Economy of Nature
The subject of ecology as a distinct area of investigation was first outlined by Linnaeus in a thesis entitled Specimen academicum de oeconomia naturae, which was defended by one of his students in 1749. Linnaeus organized ecology around the balance of nature concept, which he named the "economy of nature." He emphasized the interrelationships in nature and was one of the first naturalists to describe food chains. He also studied plant succession, the diversity of habitat requirements among species, and the selective feeding habits of insects and hoofed animals. He was strongly interested in the distribution of species and studied their different means of dispersal. He urged the application of biological knowledge not only in medicine but also in agriculture, for he believed that the effective combating of agricultural pests must be based upon a thorough knowledge of their life histories.


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