August Weismann facts for kids
Quick facts for kids
August Weismann
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| Born | 17 January 1834 Frankfurt am Main, Germany
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| Died | 5 November 1914 (aged 80) Freiburg, Germany
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| Known for | germ plasm theory |
| Awards | Darwin–Wallace Medal (Silver, 1908) |
August Friedrich Leopold Weismann (born January 17, 1834 – died November 5, 1914) was an important German biologist. Many people, like fellow German Ernst Mayr, consider him one of the most important thinkers in evolution after Charles Darwin. Weismann became the head of the Zoological Institute and the first Professor of Zoology at the University of Freiburg.
His most famous idea is the germ plasm theory. This theory says that in animals, only the special cells that create new life (called germ cells) pass on traits. Other body cells (called somatic cells) do not pass on information. This means that what an animal learns or changes during its life cannot be passed to its children. Biologists call this idea the Weismann barrier. This idea showed that the inheritance of acquired characteristics, proposed by Jean-Baptiste Lamarck, was likely not true.
The Weismann barrier idea is very important in modern biology. It helps us understand how evolution works. Weismann believed that new changes in living things come from random changes (mutations) in the germ cells. These changes then allow natural selection to happen. Weismann was one of the first biologists to completely disagree with Lamarck's ideas. His ideas came before people rediscovered Gregor Mendel's work on genetics.
Today, Weismann is highly respected. Ernst Mayr called him the most important evolutionary thinker between Darwin and the "modern evolutionary synthesis" of the 1930s and 1940s. He is seen as one of the greatest biologists ever.
Contents
Life
Early Life and Education
August Weismann was born in Frankfurt am Main, Germany, on January 17, 1834. His father, Johann Konrad Weismann, was a high school teacher. His mother, Elise, was the daughter of a mayor.
August had a typical education for his time. He learned music from age four and took drawing and painting lessons from age 14. His piano teacher was a keen butterfly collector. This teacher introduced August to collecting butterflies and caterpillars.
Studying natural sciences was too expensive and didn't offer many job chances. A family friend, chemist Friedrich Wöhler, suggested he study medicine. Thanks to money from his mother's family, August studied in Göttingen. In 1856, he finished his studies. His final paper was about how the human body makes hippuric acid.
Professional Career
After university, Weismann became an assistant at a city clinic in Rostock. He won two awards for his writings. One was about hippuric acid in plant-eating animals. The other was about the salt in the Baltic Sea. The salt paper made him decide not to become a chemist. He felt he wasn't precise enough for that field.
He traveled to Vienna, Italy (1859), and Paris (1860) to study. From 1861 to 1863, he worked as a personal doctor for Archduke Stephen of Austria. During a war in 1859, he became a Chief Medical Officer in the army. He also worked with Rudolf Leuckart at the University of Gießen. In 1868, he became a doctor with his own practice in Frankfurt.
In 1863, he started teaching comparative anatomy and zoology. By 1873, he became a full professor. He was the first person to hold the chair in zoology and direct the zoological institute at the Albert Ludwig University of Freiburg. He retired in 1912.
At first, he studied animals closely, like the development of flies. But his eyesight got worse, making it hard to use a microscope. So, he started focusing on bigger questions in biology.
Family
In 1867, August Weismann married Mary Dorothea Gruber.
Their son, Julius Weismann (1879–1950), became a composer.
Ideas on Evolution
Weismann first thought about evolution by comparing it to the idea of creationism. In his book On the justification of the Darwinian theory, he looked at both ideas. He found that many facts about living things fit well with evolution. But they were confusing if you thought they were created.
After this, Weismann accepted evolution as a fact, much like how people accepted that the Earth goes around the Sun. Weismann's ideas about how traits are passed on and how they affect evolution changed over time.
Discoveries about Cells
Weismann's ideas about germ cells and body cells make more sense when you know what other scientists were discovering. In the late 1800s, many German biologists were learning how cells divide. Scientists like Eduard Strasburger and Walther Flemming found out how cell nuclei divide. They also discovered chromosomes, which carry genetic information.
Oscar Hertwig first described meiosis in sea urchin eggs in 1876. Meiosis is a special cell division that makes germ cells. Edouard Van Beneden also described it in 1883. Weismann was the first to explain why meiosis was important for reproduction and inheritance in 1890. He realized that two cell divisions were needed to keep the number of chromosomes right. All these discoveries happened before people rediscovered Gregor Mendel's work on genetics.
Early Thoughts (1868–1881)
Like many scientists, including Charles Darwin, Weismann first thought that differences between individuals came from traits that were passed on. He believed that changes in species were directly caused by the environment. He also thought that evolution couldn't happen without changes in the environment. Weismann even used the idea of "use and disuse" of body parts, which was a Lamarckian idea.
Changing Views (1882–1895)
Weismann first rejected the idea of inheritance of acquired traits in a lecture in 1883. He tried to explain examples using both theories. For example, he noted that ant colonies have workers and soldiers that don't reproduce. Their traits can't be passed on by acquired characteristics. But the germ plasm theory explained this easily. Weismann used his theory to explain why domesticated waterfowl might have smaller wings and stronger feet.
Later Ideas (1896–1910)
Weismann studied the development of sea urchin eggs. He saw different ways cells divide, which he called equatorial division and reductional division.
His germ plasm theory says that living things have germ cells (which pass on traits) and somatic cells (which do the body's work). The germ cells are not changed by what an organism learns or by changes to its body during its life. This information is lost in each generation. This idea was called Weismannism in his time. This concept became clearer when Gregor Mendel's work on genetics was rediscovered in the early 1900s.
Awards
He received the Linnean Society of London's Darwin–Wallace Medal in 1908.
Selected publications by Weismann
- 1868. On the Justification of Darwin's Theory.
- 1872. On the Influence of Isolation on Species Formation.
- 1875. Studies on the Theory of Descent. I. On the Seasonal Dimorphism of Butterflies.
- 1876. Studies on the Theory of Descent: II. On the Ultimate Causes of Transmutations.
- 1885. The Continuity of the Germ-Plasm as the Basis of a Theory of Heredity.
- 1887. On the Question of the Inheritance of Acquired Characteristics.
- 1887. On the Number of Polar Bodies and Their Significance for Heredity.
- 1889. Essays upon Heredity.
- 1892. The Germ-Plasm: A Theory of Heredity.
- 1892. Essays on Heredity and Related Biological Questions.
- 1893. The All-Sufficiency of Natural Selection: A Reply to Herbert Spencer.
- 1902. Lectures on the Theory of Descent.
Images for kids
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August Weismann
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Essays on Heredity and Related Biological Questions, 1892
See also
In Spanish: August Weismann para niños
