Endosymbiotic theory
The underlying theme of endosymbiotic theory, as formulated in 1966, was interdependence and cooperative existence of multiple prokaryotic organisms; one organism engulfed another, yet both survived and eventually evolved over millions of years into eukaryotic cells. Her 1970 book, Origin of Eukaryotic Cells, discusses her early work pertaining to this organelle genesis theory in detail. Currently, her endosymbiotic theory is recognized as the key method by which some organelles have arisen (see endosymbiotic theory for a discussion) and is widely accepted by mainstream scientists. The endosymbiotic theory of organogenesis gained strong support in the 1980s, when the genetic material of mitochondria and chloroplasts was found to be different from that of the symbiont's nuclear DNA.[4]
In 1995, prominent Neo-Darwinist, 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.[5] ”
[edit] Theory of symbiotic relationships driving evolution
She later formulated a theory to explain how symbiotic relationships between organisms of often different phyla or kingdoms are the driving force of evolution. Genetic variation is proposed to occur mainly as a result of transfer of nuclear information between bacterial cells or viruses and eukaryotic cells. While her organelle genesis ideas are widely accepted, symbiotic relationships as a current method of introducing genetic variation is something of a fringe idea. However, examination of the results from the Human Genome Project lends some credence to an endosymbiotic theory of evolution—or at the very least Margulis's endosymbiotic theory is the catalyst for current ideas about the composition of the human genome. Significant portions of the human genome are either bacterial or viral in origin—some clearly ancient insertions, while others are more recent in origin. This strongly supports the idea of symbiotic—and more likely parasitic—relationships being a driving force for genetic change in humans, and likely all organisms. It should be noted that while the endosymbiotic theory has historically been juxtaposed to Neo-Darwinism as a competitor, the two theories are not irreconcilable. An emerging synthesis holds that natural selection works on many levels (genetic up to the ecosystem) and variation is introduced both at the genetic and the cellular level.
She does, however, hold a negative view of certain interpretations of Neo-Darwinism, excessively focused on inter-organismic competition, as she believes that history will ultimately judge them as comprising "a minor twentieth-century religious sect within the sprawling religious persuasion of Anglo-Saxon Biology."[6] She also believes that proponents of the standard theory "wallow in their zoological, capitalistic, competitive, cost-benefit interpretation of Darwin - having mistaken him... Neo-Darwinism, which insists on (the slow accrual of mutations by gene-level natural selection), is a complete funk."[7]
She opposes such competition-centric views of evolution, stressing the importance of symbiotic or cooperative relationships between species.
Margulis, Lynn and Dorion Sagan, 2007, Dazzle Gradually: Reflections on the Nature of Nature, Sciencewriters Books, ISBN 978-1-933392-31-8
Margulis, Lynn and Eduardo Punset, eds., 2007 Mind, Life and Universe: Conversations with Great Scientists of Our Time, Sciencewriters Books, ISBN 978-1-933392-61-5
Margulis, Lynn, 2007, Luminous Fish: Tales of Science and Love, Sciencewriters Books, ISBN 978-1-933392-33-2
Margulis, Lynn and Dorion Sagan, 2002, Acquiring Genomes: A Theory of the Origins of Species, Perseus Books Group, ISBN 0-465-04391-7
Margulis, Lynn, et al., 2002, The Ice Chronicles: The Quest to Understand Global Climate Change, University of New Hampshire, ISBN 1-58465-062-1
Margulis, Lynn, 1998, Symbiotic Planet : A New Look at Evolution, Basic Books, ISBN 0-465-07271-2
Margulis, Lynn and Karlene V. Schwartz, 1997, Five Kingdoms: An Illustrated Guide to the Phyla of Life on Earth, W.H. Freeman & Company, ISBN 0-613-92338-3
Margulis, Lynn and Dorian Sagan, 1997, What Is Sex?, Simon and Shuster, ISBN 0-684-82691-7
Margulis, Lynn and Dorion Sagan, 1997, Slanted Truths: Essays on Gaia, Symbiosis, and Evolution, Copernicus Books, ISBN 0-387-94927-5
Sagan, Dorion and Lynn Margulis, 1993, The Garden of Microbial Delights: A Practical Guide to the Subvisible World, Kendall/Hunt, ISBN 0840385293
Margulis, Lynn, 1992, Symbiosis in Cell Evolution: Microbial Communities in the Archean and Proterozoic Eons, W.H. Freeman, ISBN 0-7167-7028-8
Margulis, Lynn, ed, 1991, Symbiosis as a Source of Evolutionary Innovation: Speciation and Morphogenesis, The MIT Press, ISBN 0-262-13269-9
Margulis, Lynn and Dorion Sagan, 1991, Mystery Dance: On the Evolution of Human Sexuality, Summit Books, ISBN 0-671-63341-4
Margulis, Lynn and Dorion Sagan, 1987, Microcosmos: Four Billion Years of Evolution from Our Microbial Ancestors, HarperCollins, ISBN 0-04-570015-X
Margulis, Lynn and Dorion Sagan, 1986, Origins of Sex : Three Billion Years of Genetic Recombination, Yale University Press, ISBN 0-300-03340-0
Margulis, Lynn, 1982, Early Life, Science Books International, ISBN 0-86720-005-7
Margulis, Lynn, 1970, Origin of Eukaryotic Cells, Yale University Press, ISBN 0-300-01353-1
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cuando una rafaga del pensamiento nos pasa al lado se puede sentir que valio la pena haber vivido, y cuando ese pensamiento se convierte en sueńo no paramos de sońar hasta realizarlo
Edited by cactu (05/09/08 05:05 PM)
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