In the 1960’s, Lynn Margulis was able to greatly advance the work that constitute this theory of the origins of mitochondria in animals and chloroplasts in plants. Although like several other theories in biology, hers was not accepted immediately at first, scientists now see and appreciate what she discovered. Put into simpler terms, the endosymbiotic theory states the origins of eukaryotic cells such as the ones stated previously. Among the many different organelles found in eukaryotic cells, mitochondria is one of them. Proteobacteria is where mitochondria is considered to have originated due to endosymbiosis. Endosymbiosis is simply when one organism lives inside another and they mutually benefit each other. Chloroplasts was also able to originate due to endosymbiosis, however since it’s found in plants it would be from cyanobacteria (Fossil Museum, N.d.).
Both these organelles were once free-living prokaryotic cells. However because of endosymbiosis, through one way or another, they ended up inside another cell. Instead of one cell dying, they thrived by living together and now they can’t survive without one another because they both provide needed benefits (Warring, 2018). Now, why is it believed that that these organelles were once free-living organisms? Well, that is supported for several reasons. To begin with, the genes found in organelles are very similar to those of modern day prokaryotes. Also, both divide and replicate in similar ways and have similar membranes as well (Editors, 2018).
Although the exact time when this occurred is debated a lot, the fact that it happened holds true due to all the evidence that proves the theory. It can get complicated though because this process isn’t a one time thing. It can happen several times and to trace that seems nearly impossible. Which is why, trying to do so does not get exact results therefore making it a challenging topic to fully understand. Something that is also debated a lot when referring to this topic is from what eukaryotic domain these prokaryotes originated from (Fossil Museum, 2018). Whatever the case, the endosymbiotic theory is important in biology to further understand how it is that life originated and evolved.
Editors. (2018). Endosymbiotic Theory Definition. Retrieved from https://biologydictionary.net/endosymbiotic-theory/
Fossil Museum. (N.d.). Endosymbiosis – The Appearence of the Eukaryotes. Retrieved from http://www.fossilmuseum.net/Evolution/Endosymbiosis.htm
Warring, S. (2018). Endosymbiotic Theory. Retrieved from https://askabiologist.asu.edu/explore/cells-living-in-cells
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