EVOLUCION ENDOSIMBIOTICA PDF

I t is believed that all organisms have evolved from a cell type that appeared about x10 6 years ago, known as LUCA Last Universal Common Ancestor. This cell must have been simple and supposedly similar to the current prokaryotes. However, the complexity of some of these early cells increased with time and led to eukaryotic cells. Current eukaryotic cells have internal membrane-bound compartments such as nucleus, organelles like endoplasmic reticulum, Golgi apparatus, endosomes, mitochondria, chloroplasts, as well as cytoskeleton.

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Lynn Margulis born Lynn Petra Alexander ; [2] [3] March 5, — November 22, [4] was an American evolutionary theorist, biologist, science author, educator, and science popularizer, and was the primary modern proponent for the significance of symbiosis in evolution. Historian Jan Sapp has said that "Lynn Margulis's name is as synonymous with symbiosis as Charles Darwin 's is with evolution.

Margulis was also the co-developer of the Gaia hypothesis with the British chemist James Lovelock , proposing that the Earth functions as a single self-regulating system, and was the principal defender and promulgator of the five kingdom classification of Robert Whittaker. Called "Science's Unruly Earth Mother", [8] a "vindicated heretic", [9] or a scientific "rebel", [10] Margulis was a strong critic of neo-Darwinism. Williams , and John Maynard Smith.

Many of her major works, particularly those intended for a general readership, were collaboratively written with her son Dorion Sagan. Lynn Margulis was born in Chicago , to a Jewish , Zionist family.

She was the eldest of four daughters. Her father was an attorney who also ran a company that made road paints. Her mother operated a travel agency. A precocious child, she was accepted at the University of Chicago Laboratory Schools [17] at the age of fifteen. She joined the University of Wisconsin to study biology under Hans Ris and Walter Plaut, her supervisor, and graduated in with an MS in genetics and zoology.

Her first publication was with Plaut, on the genetics of Euglena , published in in the Journal of Protozoology. Before she could complete her dissertation, she was offered research associateship and then lectureship at Brandeis University in Massachusetts in It was while working there that she obtained her PhD from the University of California, Berkeley in She was promoted to Associate Professor in , to full Professor in , and to University Professor in She was Distinguished Professor of Biology in In she transferred to the Department of Geosciences at Amherst to become Distinguished Professor of Geosciences "with great delight", [23] the post which she held until her death.

Margulis married astronomer Carl Sagan in soon after she got her bachelor's degree. Sagan was then a graduate student in physics at the University of Chicago.

Their marriage ended in , just before she completed her PhD. They had two sons, Dorion Sagan , who later became a popular science writer and her collaborator, and Jeremy Sagan, software developer and founder of Sagan Technology. In , she married Thomas N. Margulis, a crystallographer. No one can do it — something has to go. She was a religious agnostic , [16] and a staunch evolutionist. But she rejected the modern evolutionary synthesis , [11] and said: "I remember waking up one day with an epiphanous revelation: I am not a neo-Darwinist!

I recalled an earlier experience, when I realized that I wasn't a humanistic Jew. Although I greatly admire Darwin's contributions and agree with most of his theoretical analysis and I am a Darwinist, I am not a neo-Darwinist. Margulis died on 22 November at home in Amherst , Massachusetts , five days after suffering a hemorrhagic stroke. Weathering constant criticism of her ideas for decades, Margulis was famous for her tenacity in pushing her theory forward, despite the opposition she faced at the time.

In , English evolutionary biologist Richard Dawkins had this to say about Lynn Margulis and her work:. I greatly admire Lynn Margulis's sheer courage and stamina in sticking by the endosymbiosis theory, and carrying it through from being an unorthodoxy to an orthodoxy. I'm referring to the theory that the eukaryotic cell is a symbiotic union of primitive prokaryotic cells. This is one of the great achievements of twentieth-century evolutionary biology, and I greatly admire her for it.

Margulis opposed competition-oriented views of evolution, stressing the importance of symbiotic or cooperative relationships between species. She later formulated a theory that proposed symbiotic relationships between organisms of different phyla or kingdoms as the driving force of evolution , and explained genetic variation as occurring mainly through transfer of nuclear information between bacterial cells or viruses and eukaryotic cells. Margulis also held a negative view of certain interpretations of Neo-Darwinism that she felt were excessively focused on competition between organisms, as she believed that history will ultimately judge them as comprising "a minor twentieth-century religious sect within the sprawling religious persuasion of Anglo-Saxon Biology.

Neo-Darwinism, which insists on [the slow accrual of mutations by gene-level natural selection], is in a complete funk. Margulis initially sought out the advice of Lovelock for her own research: she explained that, "In the early seventies, I was trying to align bacteria by their metabolic pathways.

I noticed that all kinds of bacteria produced gases. Oxygen, hydrogen sulfide, carbon dioxide, nitrogen, ammonia—more than thirty different gases are given off by the bacteria whose evolutionary history I was keen to reconstruct. Why did every scientist I asked believe that atmospheric oxygen was a biological product but the other atmospheric gases—nitrogen, methane, sulfur, and so on—were not? Lovelock believed that the gases in the atmosphere were biological.

Margulis met with Lovelock, who explained his Gaia hypothesis to her, and very soon they began an intense collaborative effort on the concept. Like other early presentations of Lovelock's idea, the Lovelock-Margulis paper seemed to give living organisms complete agency in creating planetary self-regulation, whereas later, as the idea matured, this planetary-scale self-regulation was recognized as an emergent property of the Earth system , life and its physical environment taken together.

In her book Symbiotic Planet , Margulis explored the relationship between Gaia and her work on symbiosis. Since , life on earth was classified into five kingdoms , as introduced by Robert Whittaker.

She rejected the three-domain system introduced by Carl Woese in , which gained wide acceptance. She introduced a modified classification by which all life forms, including the newly discovered, could be integrated into the classical five kingdoms. According to her the main problem, archaea, falls under the kingdom Prokaryotae alongside bacteria in contrast to the three-domain system, which treats archaea as a higher taxon than kingdom, or the six-kingdom system, which holds that it is a separate kingdom.

The following describes three of these controversies. In , via a then-standard publication-process known as "communicated submission" which bypassed traditional peer review , she was instrumental in getting the Proceedings of the National Academy of Sciences PNAS to publish a paper by Donald I. Williamson rejecting "the Darwinian assumption that larvae and their adults evolved from a single common ancestor.

What it may do is broaden the discussion on how metamorphosis works and PNAS stated that the decision had nothing to do with the Williamson controversy. In a Discover Magazine interview which was published less than six months before her death, Margulis explained to writer Dick Teresi her reason for interest in the topic of "AIDS" paper: "I'm interested in spirochetes only because of our ancestry.

However, in the Discover Magazine interview Margulis said that "the set of symptoms, or syndrome, presented by syphilitics overlaps completely with another syndrome: AIDS," and also noted that Kary Mullis [a] said that "he went looking for a reference substantiating that HIV causes AIDS and discovered, 'There is no such document.

Margulis argued that the September 11 attacks were a "false-flag operation, which has been used to justify the wars in Afghanistan and Iraq as well as unprecedented assaults on From Wikipedia, the free encyclopedia.

American evolutionary biologist. Chicago , Illinois , U. Amherst, Massachusetts , U. Carl Sagan m. Thomas Margulis m. Main article: Symbiogenesis. Main article: Symbiosis. See also: Horizontal gene transfer. Further information: Gaia hypothesis.

The standard author abbreviation Margulis is used to indicate this individual as the author when citing a zoological name. The Endosymbiotic Hypothesis: A biological experience. Charles A. Ferguson, University of Colorado Denver. Retrieved September 16, The New York Times. Retrieved 25 July Bibcode : Natur. Bibcode : Sci White River Junction: Chelsea Green. What Evolution Is.

The Register. Retrieved 19 December Discover Magazine. Discover Interview. April Retrieved 22 July The Quarterly Review of Biology. Retrieved 1 May Jason G. Retrieved 14 September Encyclopedia of World Scientists Revised ed. New York: Facts on File. Soylent Communications. Retrieved 18 December University of Chicago Magazine. Archived from the original on 23 July Encyclopedia of World Biography. Series 5. BBC Radio 4.

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