To many, prokaryotes may seem as uninteresting, insignificant organisms, but to biologists, prokaryotes have the greatest success story in the history of life.
Prokaryotes have been around for at least 3.5 billion years, considering that the earth is over 4.5 billion years old. They are the earliest known organisms to ever inhabit the earth. Still small and insignificant they may seem, they have been able to endure and evolve on their own for over 2 billion years. They have produced a substantial impact on all life as we know on earth, and they have been able to go on to survive and adapt to an ...view middle of the document...
American biologist, Ivan Emmanuel Wallin, also contributed to the endosymbiotic theory by being the first to suggest that a eukaryotic cell is composed of microorganisms. His idea was outstanding to the endosymbiotic theory. He was likewise able to explain that bacteria could be the main cause of the parentage of the species, thus implying that the organization of a species can occur through endosymbiosis.
Ivan Wallin in collaboration with Konstantin Mereschkowsky, formed the idea of symbiogenesis with their publication, “Symbiogenesis and the beginning of the species”. Their theories were rejected as it was believed that mitochondria and chloroplasts do not contain any of their own DNA. All the same, the theory was then conveyed back to life in the 1960s when Hans Ris was able to turn out that mitochondria and chloroplasts do in fact contain DNA.
The publication of her work, “Symbiosis in cell evolution” led Dr. Lynn Margulis to become the guiding name behind the endosymbiotic theory. Her work on mitochondria was able to supply evidence that mitochondria were originally separate organisms that went into a symbiotic relationship with an ancestral host cell.
Granting to the endosymbiotic theory, the organelles of eukaryotic cells, i.e. Mitochondria and chloroplasts, were originally free-living prokaryotic organisms that now share an endosymbiotic relationship with their legions. The theory speculates that mitochondria evolved from aerobic bacteria, most likely Proteobacteria. It also speculates that chloroplasts probably evolved from cyanobacteria, which are autotrophic prokaryotes. In both these cases it is assumed that these free-living prokaryotic organisms were ingested by large anaerobic bacteria which could not exist in an aerobic environment.
This hypothesis has been broadly accepted as there is compelling evidence for this theory, as the similarities between prokaryotes, eukaryotes and organelles is astounding. Prokaryotes together with mitochondria and chloroplasts have one single circular chromosome as opposed to a eukaryotic cell that holds a nucleus with more than one chromosome. Binary fission, a procedure of cell division, is present not only in prokaryotes, but also in mitochondria and chloroplasts. A eukaryotic cell, however, would divide by mitosis or meiosis. The ribosomes present in prokaryotes as well as mitochondria and chloroplasts are that of “70 S”, whereas eukaryotic cells contain “80 S” ribosomes. The electron transport chain, found in the plasma membrane around the cell, is only present in mitochondria, chloroplasts and prokaryotes. ...