This Wiki was written by Dillon Riebel, Austin Fogle, Filiberto Morales, and Kevin Huang in order to answer the question: What is the Endosymbiotic Hypothesis?  This site will be separated into sections on the History, Evidence, Criticism/Other Theories, and Further Applications of the Hypothesis, as well as the difference between Primary and Secondary Endosymbiosis.

But first, a short overview of what the Endosymbiotic Hypothesis actually states:

The goal of the Endosymbiotic Hypothesis is to explain the origins of eukaryotic cells and their organelles, particularly chloroplasts and mitochondria.  First proposed by Russian botanist Konstantin Mereschkowski in 1905 and further expanded on by Lynn Margulis in 1967, the hypothesis states that the organelles of eukaryotic cells came to be via symbiosis between separate microorganisms.  This means that chloroplasts and mitochondria originally lived as separate bacterial organisms that were absorbed by other cells.  These organelles then continued to live inside (endo) the larger cell as units called endosymbionts.  The fact that each component benefited the other (symbiosis) allowed the new eukaroytic cell to grow and reproduce, passing on these newely aquired organelles to the next generation.


The Endosymbiotic Hypothesis has been debated and challenged over the last half century since it was originally conceived, with convincing evidence both for and against the idea being constantly presented.  Still, the Hypothesis has garnered more support than criticism, leading many to consider it worthy of the title of “Theory”.

Regardless of whether or not the Endosymbiotic Hypothesis is fully supported, it provides compelling explanations for how eukaryotes came to be, as well as the origins of organized life on our planet.

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