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Lynn Margulis: Biography, Theory & Discovery

Instructor: Bridgett Payseur

Bridgett has a PhD in microbiology and immunology and teaches college biology.

Lynn Margulis helped champion the evolutionary concept of endosymbiosis, describing how parts of the cell came to exist. Read on to learn about the life and ideas of this brilliant trailblazer.

The Life of Lynn Margulis

While Lynn Margulis may not be a household name, she led a life devoted to science. She developed endosymbiotic theory, which helped clarify complex evolutionary concepts and challenged long-held ideas.

Lynn Margulis was born Lynn Petra Alexander on March 5, 1938, in Chicago, Illinois. She attended the University of Chicago Laboratory Schools and graduated with her bachelor's degree at 18. One of her favorite courses was on genetics and heredity, which she took with James Watson, who later discovered the structure of DNA.

She met a physics student named Carl Sagan in Chicago and married him at age 19. They attended the University of Wisconsin-Madison, where Margulis got her Master's degree in zoology and genetics. They next attended the University of California-Berkeley, where Margulis began her PhD in genetics.

She completed her PhD in 1965 and began working at Boston University. She stayed at Boston University for 22 years before moving to the University of Massachusetts, Amherst. Her marriage to Sagan ended in 1963. She married Thomas Margulis in 1967, and they divorced in 1980.

Margulis received many honors for her work. She was a recipient of the 1999 National Medal of Science. She was also a member of the US National Academy of Sciences and received the Darwin-Wallace Medal of the Linnean Society of London. Lynn Margulis died of a stroke on November 22, 2011.

Endosymbiotic Theory

Margulis was an evolutionary biologist. She was most interested in the effect of symbiosis on evolution. 'Sym' means together, and 'biosis', of course, means living. So, symbiosis describes how two organisms live together. She was particularly interested in a part of the cell called the mitochondria, which helps make energy for the cell. Upon seeing a mitochondrion, she noted that it looked like a bacterium.

Margulis hypothesized that a free-living bacterium had 'moved in' with an ancestral eukaryote, and eventually became a part of it. The bacteria took over the job of energy production. In plant cells, bacteria also moved in and became chloroplasts, the organelle that performs photosynthesis. She published these ideas in her 1970 book Origin of Eukaryotic Cells.

This process was called endosymbiosis, which means one organism lives inside another. In this case, a free-living bacterium was living inside a larger eukaryotic cell. At first, this hypothesis was ridiculed by others. The long-standing ideas of scientists at the time thought that evolution only happened slowly, by random chance mutations. However, new genetic tools allowed scientists to compare the DNA found in mitochondria and in bacteria. They found a very close relationship, indicating that Margulis was probably correct. The concept of endosymbiosis is now widely accepted among evolutionary scientists.

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