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Line 16: − − == History == − − The endosymbiotic theory was first articulated by famed [[Russian]] botanist Konstantin Mereschkowski in 1905<ref>Mereschkowski C (1905). "Über Natur und Ursprung der Chromatophoren im Pflanzenreiche". Biol Centralbl 25: 593–604.</ref>. Mereschkowski based his theory in part on work done by botanist Andreas Schimper, who had observed in 1883 that the division of chloroplasts in green [[plants]] closely resembled that of cyanobacteria. Schimper had himself tentatively proposed (in a footnote) that green plants could have arisen from the symbiosis of two simpler organisms.<ref>Schimper AFW (1883). "Über die Entwicklung der Chlorophyllkörner und Farbkörper". Bot. Zeitung 41: 105–14, 121–31, 137–46, 153–62.</ref> In the 1920s, Irvin Wallin, a [[professor]] at the University of Colorado Medical School, extended the idea of an endosymbiotic origin to the mitochondria.<ref>Wallin IE (1923). "The Mitochondria Problem". The American Naturalist 57 (650): 255–61. doi:10.1086/279919. − </ref> These theories were initially dismissed (or ignored) by the scientific community. More detailed electron microscopic comparisons between cyanobacteria and chloroplasts (for example, studies by Hans Ris<ref>Ris H, Singh RN (January 1961). "Electron microscope studies on blue-green algae". J Biophys Biochem Cytol 9 (1): 63–80. doi:10.1083/jcb.9.1.63. PMC 2224983. PMID 13741827.</ref>) combined with the discovery that plastids and mitochondria contain their own [[DNA]]<ref>Stocking C and Gifford E (1959). "Incorporation of thymidine into chloroplasts of Spirogyra". Biochem. Biophys. Res. Comm. 1 (3): 159–64. doi:10.1016/0006-291X(59)90010-5. − </ref> (which had recently been identified as the hereditary material of organisms) led to a resurrection of the idea in the 1960s. − − The endosymbiotic theory was advanced and substantiated with [[microbiology|microbiological]] evidence in 1967 by [[American]] biologist Lynn Margulis. A young faculty member at [[Boston University]], Margulis authored a theoretical paper entitled ''The Origin of Mitosing Eukaryotic Cells''<ref>Lynn Sagan (1967). "On the origin of mitosing cells". J Theor Bio. 14 (3): 255–274. doi:10.1016/0022-5193(67)90079-3. PMID 11541392.</ref>. The paper, however, was "rejected by about fifteen scientific journals," Margulis recalled<ref>John Brockman, The Third Culture, New York: Touchstone, 1995, 135.</ref>(see [[Best of the Public]]). It was finally accepted by ''The Journal of Theoretical Biology'' and is considered today a landmark in modern endosymbiotic theory. Drawing heavily from the ideas of Mereschkowski and Wallin, Margulis's endosymbiotic theory formulation is the first to rely on direct microbiological observations as opposed to [[paleontology|paleontological]] or [[zoology|zoological]] observations, which were previously the norm for new works in [[evolutionary biology]]. − − The possibility that peroxisomes may have an endosymbiotic origin has also been considered, although they lack DNA. Christian de Duve proposed that they may have been the first endosymbionts, allowing cells to withstand growing amounts of free molecular [[oxygen]] in the [[Earth|Earth's]] atmosphere. However, it now appears that they may be formed ''de novo'', contradicting the idea that they have a symbiotic origin<ref>Gabaldón T, Snel B, van Zimmeren F, Hemrika W, Tabak H, Huynen MA (2006). "Origin and evolution of the peroxisomal proteome". Biol. Direct 1 (1): 8. doi:10.1186/1745-6150-1-8. PMC 1472686. PMID 16556314. (Provides evidence that contradicts an endosymbiotic origin of peroxisomes. Instead it is suggested that they evolutionarily originate from the Endoplasmic Reticulum)</ref>. It is believed that over millennia these endosymbionts transferred some of their own DNA to the host cell's nucleus during the evolutionary transition from a symbiotic community to an instituted eukaryotic cell (called "serial endosymbiosis"). This hypothesis is thought to be possible because it is known today from scientific observation that transfer of DNA occurs between [[bacteria]] species, even if they are not closely related. Bacteria can take up DNA from their surroundings and have a limited ability to incorporate it into their own [[genome]].
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The endosymbiont theory implies that there should be considerable autonomy for mitochondria. This is not the case. Mitochondria are far from self-sufficient even in their DNA, which is their most autonomous feature. Mitochondria actually have most of their proteins coded by nuclear genes, including their DNA synthesis enzymes.<ref>http://creation.com/mitochondria-created-to-energize-us</ref>}}
The endosymbiont theory implies that there should be considerable autonomy for mitochondria. This is not the case. Mitochondria are far from self-sufficient even in their DNA, which is their most autonomous feature. Mitochondria actually have most of their proteins coded by nuclear genes, including their DNA synthesis enzymes.<ref>http://creation.com/mitochondria-created-to-energize-us</ref>}}
== Problems ==
== Problems ==