Everything about Wilhelm Johannsen totally explained
Wilhelm Johannsen (
February 3,
1857 -
November 11,
1927) was a
Danish botanist, plant physiologist and
geneticist. He was born in Copenhagen. Very young, he was apprenticed to a
pharmacist in 1872 and worked in
Denmark and
Germany, passing his pharmacist's exam in 1879. In 1881, he became assistant in the chemistry department at the
Carlsberg Laboratory under the chemist
Johan Kjeldahl. Johannsen studied the
metabolism of
dormancy and
germination in
seeds,
tubers and
buds. He showed that
dormancy could be broken by various
anesthetic compounds, such as
diethyl ether and
chloroform.
In 1892, he was appointed lecturer at
Royal Veterinary and Agricultural University and later became professor of
botany and
plant physiology. He taught plant physiology. His most well-known research concerned so-called
pure lines of the self-fertile
common bean. He was able to show that even in
populations
homozygous for all traits, for example without genetic variation, seed size followed a
normal distribution. This was attributable to resource provision to the mother plant and to the position of seeds in
pods and of pods on the plant. This led him to coin the terms
phenotype and
genotype. His findings led him to oppose contemporary
Darwinists, most notably
Francis Galton and
Karl Pearson, who held the occurrence of
normal distributed trait variation in
populations as proof of gradual genetic variation on which selection could act. Only with the
modern evolutionary synthesis, it was established that variation need tobe
heritable to act as the raw material for
selection.
The terms
phenotype and
genotype were created by Wilhelm Johannsen and first used in his paper
Om arvelighed i samfund og i rene linier and in his book
Arvelighedslærens Elementer. This book was rewritten, enlarged and translated to German as
Elemente der exakten Erblichkeitslehre. It was in this book Johannsen introduced the term
gene. This term was coined in opposition to the then common
pangene that stemmed from
Darwin's theory of
pangenesis. The book became one of the founding texts of genetics.
Also in 1905, Johannsen was appointed professor of
plant physiology at the
University of Copenhagen , becoming vicechancelor in 1917. In December 1910, Johannsen was invited to give an address before the
American Society of Naturalists. This talk was printed in the
American Naturalist. In 1911, he was invited to give a series of four lectures at
Columbia University
Miscellaneous
Corresponding member of the
Academy of Natural Sciences of Philadelphia (elected 1915).
Further Information
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