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Symbiogenesis was first formulated by K. S. Mereschkovsky (1855-1921) in his 1926 book "Symbiogenesis and the Origin of Species" and by Ivan Wallin , in "Symbionticism and the Origins of Species". Ivan Wallin proposed in 1927 that bacteria might represent the fundamental cause of the origin of species, and that the creation of a species may occur via endosymbiosis.
In the late 20th century, Lynn Margulis claimed that microorganismA micro-organism or microbe is an organism that is so small that it is invisible to the naked eye. The term is synonymous by usage to single- celled organism and unicellular organism even though some unicellular protists are visible to the naked eye, ands are one of the major evolutionary forces in the origin of species, endosymbiosis of bacteria being responsible for the creation of complex forms of lifeAlternate uses: see Life (disambiguation) and Living (disambiguation Life is a multi-faceted concept with no simple definition; this article is confined to the primary meanings in biology; articles on life in other senses are included in the article life.
Margulis emphasizes that bacteria and other microorganisms actively participated in shaping the EarthEarth also known as the Earth or Terra is the planet on which we live, the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harbouring life. The pla, and helped create conditions suitable for life (e.g., almost all eukaryoteEukaryotes are organisms with complex cells, in which the genetic material is organized into membrane-bound nuclei. They include the animals, plants, and fungi, which are mostly multicellular, as well as various other groups called protists, many of whichs require oxygenOxygen is the chemical element in the periodic table that has the symbol O and atomic number 8. The element is very common, found not only on Earth but throughout the universe. Molecular oxygen (O, often called free oxygen on Earth is thermodynamically un, and only developed after cyanobacteriaCyanobacteria are a phylum of aquatic bacteria that obtain their energy through photosynthesis. They are often referred to as blue-green algae even though it is now known that they are not related to any of the other algal groups, which are all eukaryotes have produced enough atmosphericEarth's atmosphere is the layer of gases surrounding the planet Earth and retained by the Earth's gravity. It consists of nitrogen (78. 1% by volume) and oxygen (20. 9%), with small amounts of argon (0. 9%), carbon dioxide (variable, but around 0. 035%), oxygen). She also argues that these microorganisms still maintain current conditions and that they constitute a major component in Earth biomassBiomass is the organic non- fossil material of biological origin, collectively. For example, plants (including trees) and animals are biomass, as are the materials they produce, such as animal droppings and wood. The most successful animal of the earth, i.
She showed that free-living bacteria and other microorganisms tend to merge with larger life forms, seasonally and occasionally, or permanently, perhaps under stress conditions. In the now generally accepted endosymbiotic theory, Margulis demonstrated that current plant cells resulted from the merging of separate ancestors, the chloroplast evolving from endosymbiotic cyanobacteria (autotrophic prokaryotes). A more recent additional hypothesis for the origin of some algal and plant cells is the fusion of Thermoplasma ( sulfur reduction , fermentation), Spirochaeta ( motility ), alpha-proteobacteria ( oxygen respiration) and Synechococcus cyanobacteria ( photosynthesis).
Margulis claims that most of the DNA found in the cytoplasm of animal, plant, fungal and protoctist cells originated as genes of bacteria that became organelles, rather than from genetic drift or mutation.
Along these lines Margulis has argued that bacteria have the ability to exchange genes very easily and quickly, even between different species, by conjugation or through plasmids. For these reasons, the genetic material of bacteria is much more versatile than that of the eukaryote (see Primary nutritional groups for more on the extent of bacterial ability in terms of nutrition). Margulis claims that versatility is the process which enabled life to evolve so quickly, as bacteria were able to adapt to initial conditions of environment and to new changes by other bacteria.