Symbiogenesis

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Under symbiogenesis means the fusion of two or more different organisms in a single new organism . The theory of symbiogenesis was founded by the German botanist Andreas Franz Wilhelm Schimper in 1883 and the Russian biologist Konstantin Mereschkowsky in 1905. It was taken up in 1922 by the American biologist Ivan Wallin and around 1970 by Lynn Margulis . The theory of symbiogenesis is a supplement to the theory of evolution in that the emergence of new cell organelles, organs or species is traced back to the symbiotic relationship and the union between individual species. Accordingly, symbiogenesis gives rise to the possibility that family trees can not only branch, but also network again.

  • A well-known example of symbiogenesis are the lichens as associations between fungi and green algae or cyanobacteria .
  • The endosymbiotic theory includes another scientifically recognized example of symbiogenesis. According to this, the origin of certain organelles ( mitochondria and plastids ) of the eukaryotic cell lies in the fact that single cells without a nucleus were incorporated into pre- eukaryotic primordial cells through endocytosis . Endosymbiosis leads to an increase in morphological complexity and enables those cells that take up or fuse with others to be enriched with genetic material and thus an increase in the genetic information available within a species.
  • In symbioses, especially with prokaryotes , horizontal gene transfer (or more precisely endosymbiotic gene transfer, EGT) can also occur. This is a further possibility of enrichment with genetic material, which was recognized by Carl Woese as an additional driving force, especially in early evolution .
  • In addition, Lynn Margulis and other proponents of the theory also assume that flagella and cilia of eukaryotes could have developed from endosymbiotic spirochetes . This hypothesis is controversial among evolutionary biologists , since there is apparently no independent DNA in the organelles . An originally alleged find could never be reproduced.
  • As the example of Epixenosomen (to the Verrucomicrobia bacteria belonging) of the eyelashes animalcule Euplotidium shows such intimate are Ektosymbiosen in microbial area but possible in principle.
  • As the DNA-less plastids of the non-photosynthetically active green alga Polytomella ( Chlamydomonadales , syn. Volvocales), most hydrogenosomes and all mitosomes (both from the mitochondrial relationship) show, the total loss of DNA is possible. An alleged DNA find could also be refuted in the case of the mitosomes. In these cases, however, the decisive factor is the detection of (previously) transferred to the cell nucleus DNA of the organelle, which is homologous to that of similar organelles ( with their own DNA) in other species (see biosignature : chemical fossils).

According to Lynn Margulis and Dorion Sagan, life did not take over the globe by combat, but by networking , rather than through struggle .

Individual evidence

  1. ↑ Andreas Franz Wilhelm Schimper : About the development of the chlorophyll grains and color bodies . In: Bot. Newspaper . 41, 1883, pp. 105-114, 121-131, 137-146, 153-162. (via WebArchive)
  2. ↑ Constantin S. Mereschkowsky: About the nature and origin of the chromatophores in the plant kingdom . In: Biologosches Centralblatt . 25, September 15, 1905, pp. 593-604. (via WebArchive)
  3. ↑ Sapp J, Carrapiço F, Zolotonosov M: Symbiogenesis: the hidden face of Constantin Merezhkowsky . In: History and philosophy of the life sciences . 24, No. 3-4, 2002, pp. 413-440. PMID 15045832 .
  4. ↑ Ivan E. Wallin: On the nature of mitochondria. I. Observations on mitochondria staining methods applied to bacteria. II. Reactions of bacteria to chemical treatment . In: American Journal of Anatomy . 30, No. 2, 1922, pp. 203-229. doi : 10.1002 / aja.1000300203 .
  5. ↑ Ivan E. Wallin: On the nature of mitochondria. III. The demonstration of mitochondria by bacteriological methods. IV. A comparative study of the morphogenesis of root-nodule bacteria and chloroplasts . In: American Journal of Anatomy . 30, No. 4, 1922, pp. 451-471. doi : 10.1002 / aja.1000300404 .
  6. ↑ See the model of the Macroevolution Synade in Ulrich Kutschera : "Symbiogenesis, natural selection, and the dynamic Earth", "Theory in Biosciences", vol. 128, no. 3 / August 2009, doi : 10.1007 / s12064-009-0065 -0 , pp. 191-203.
  7. ↑ Peter Sitte: "Being, becoming and growing of the lifeworld", in: Hans Gebhardt, Helmuth Kiesel (ed.), Weltbilder , Springer, 2004, p. 92.
  8. ↑ English Epixenosomes
  9. ↑ Giovanna Rosati, Giulio Petroni, Silvia Quochi, Letizia Modeo, Franco Verni: Epixenosomes: Peculiar Epibionts of the Hypotrich Ciliate Euplotidium Itoi Defend Their Host Against Predators . In: Journal of Eukaryotic Microbiology . 46, No. 3, May 1, 1999, ISSN  1550-7408 , pp. 278-282. doi : 10.1111 / j.1550-7408.1999.tb05125.x .
  10. ↑ David Roy Smith, Robert W. Lee: A Plastid without a Genome: Evidence from the Nonphotosynthetic Green Algal Genus Polytomella . In: Plant Physiology . 164, No. 4, April 1, 2014, pp. 1812-1819. doi : 10.1104 / pp.113.233718 . PMID 24563281 . PMC 3982744 (free full text).
  11. ^ Margulis and Sagan: Microcosmos, New York 1986, p. 15.