August Weismann
August Friedrich Leopold Weismann (17 January 18345 November 1914) was a German evolutionary biologist. Fellow German Ernst Mayr ranked him as the second most notable evolutionary theorist of the 19th century, after Charles Darwin. Weismann became the Director of the Zoological Institute and the first Professor of Zoology at Freiburg.His main contribution involved germ plasm theory, at one time also known as Weismannism, according to which inheritance (in a multicellular animal) only takes place by means of the germ cells—the gametes such as egg cells and sperm cells. Other cells of the body—somatic cells—do not function as agents of heredity. The effect is one-way: germ cells produce somatic cells and are not affected by anything the somatic cells learn or therefore any ability an individual acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. Biologists refer to this concept as the Weismann barrier. This idea, if true, rules out the inheritance of acquired characteristics as proposed by Jean-Baptiste Lamarck. However, a careful reading of Weismann's work over the span of his entire career shows that he had more nuanced views, insisting, like Darwin, that a variable environment was necessary to cause variation in the hereditary material.
The idea of the Weismann barrier is central to the modern synthesis of the early 20th century, though scholars do not express it today in the same terms. In Weismann's opinion the largely random process of mutation, which must occur in the gametes (or stem cells that make them) is the only source of change for natural selection to work on. Weismann became one of the first biologists to deny Lamarckism entirely. Weismann's ideas preceded the rediscovery of Gregor Mendel's work, and though Weismann was cagey about accepting Mendelism, younger workers soon made the connection.
Weismann is much admired today. Ernst Mayr judged him to be the most important evolutionary thinker between Darwin and the evolutionary synthesis around 1930–1940, and "one of the great biologists of all time". Provided by Wikipedia
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Aufsätze über Vererbung und verwandte biologische Fragen / by Weismann, August 1834-1914, Weismann, August 1834-1914
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<<Das>> Keimplasma eine Theorie der Vererbung by Weismann, August 1834-1914
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<<Die>> Bedeutung der sexuellen Fortpflanzung für die Selektions-Theorie by Weismann, August 1834-1914
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Aufsätze über Vererbung und verwandte biologische Fragen by Weismann, August 1834-1914
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Aeussere Einflüsse als Entwicklungsreize by Weismann, August 1834-1914
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<<Die>> Allmacht der Naturzüchtung eine Erwiderung an Herbert Spencer by Weismann, August 1834-1914
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Über die Berechtigung der Darwin'schen Theorie ein akademischer Vortrag gehalten am 8. Juli 1868 in der Aula der Universität zu Freiburg im Breisgau by Weismann, August 1834-1914
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<<Die>> Continuität des Keimplasma's als Grundlage einer Theorie der Vererbung by Weismann, August 1834-1914
Published 1885Call Number: Loading…Fulltext
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Ueber die Dauer des Lebens ein Vortrag by Weismann, August 1834-1914
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Ueber den Einfluss der Isolirung auf die Artbildung by Weismann, August 1834-1914
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Studien zur Descendenz-Theorie by Weismann, August 1834-1914
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Ueber die Zahl der Richtungskörper und über ihre Bedeutung für die Vererbung by Weismann, August 1834-1914
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Ueber das Wandern der Vögel by Weismann, August 1834-1914
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Über Germinal-Selection eine Quelle bestimmt gerichteter Variation by Weismann, August, 1834-1914
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Ueber das Wandern der Vögel by Weismann, August, 1834-1914
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Über die Entstehung des vollendeten Insekts in Larve und Puppe ein Beitrag zur Metamorphose der Insekten by Weismann, August, 1834-1914
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Ueber die Dauer des Lebens ein Vortrag by Weismann, August, 1834-1914
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18
Äußere Einflüsse als Entwicklungsreize by Weismann, August, 1834-1914
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Die Allmacht der Naturzüchtung eine Erwiderung an Herbert Spencer by Weismann, August, 1834-1914
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Ueber den Einfluß der Isolirung auf die Artbildung by Weismann, August, 1834-1914
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