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The '''Endosymbiotic hypothesis''' is a [[hypothesis]] used by evolutionists to explain the origin of certain cellular [[organelle]]s, specifically [[mitochondrion|mitochondria]] and [[chloroplasts]].

The '''Endosymbiotic hypothesis''' is a [[hypothesis]] used by evolutionists to explain the origin of certain [[eukaryote|eukaryotic]] [[organelle]]s, specifically [[mitochondrion|mitochondria]] and [[chloroplasts]].

Evolutionists believe that early in the course of terrestrial life, all cells were [[prokayrote]]s.

Evolutionists believe that early in the course of terrestrial life, all cells were [[prokaryote]]s.

It is hypothesized that at some point, [[endophagocytosis]] occurred whereby one bacteria "hijacked" the energy producing potential of another by engulfing a respiring or photosynthesizing bacteria. Mitochondria and chloroplasts are the only organelles to contain their own [[DNA]] (other than the nucleus, which contains the DNA for the entire cell) and their DNA is well-conserved enough that they appear to be nearly separate organisms. DNA and [[RNA]] analyses have borne out much of this hypothesis. Further evidence supporting mitochondria and chloroplasts being endosymbionts lies in the fact that both organelles have [[plasma]] membrane bound spaces inside of their outer membranes, something no other organelle possesses.  

It is hypothesized that at some point, [[endophagocytosis]] occurred whereby one bacteria "hijacked" the energy producing potential of another by engulfing a respiring or photosynthesizing bacteria.

 

Mitochondria and chloroplasts are the only organelles to contain their own [[DNA]] (other than the nucleus, which contains the DNA for the entire cell) and their DNA is well-conserved enough that they appear to be nearly separate organisms. DNA and [[RNA]] analyses have borne out much of this hypothesis; in particular, chloroplasts have a high amount of similarity with cyanobacteria (blue-green algae), and mitochondria strongly resemble proteobacteria. Some evolutionists argue that the [[nucleus]] is also the result of the endophagocytosis of an [[archaea]]. Further evidence supporting mitochondria and chloroplasts being endosymbionts lies in the fact that both organelles have [[plasma]] membrane bound spaces inside of their outer membranes, something no other organelle possesses. Many other eukaryotes have organelles which appear to have several layers of plasma membrane; evolutionists interpret this to mean that these are the result of a series of endosymbiosis events.

 

One problem with the endosymbiotic hypothesis is that endophagocytosis is not observed among existing prokaryotes.

Alternate hypotheses are that eukaryotic and prokaryotic cells were simply [[intelligent design|design]]ed as they are. This is, of course, like the endosymbiotic hypothesis, neither [[theory|testable]] nor [[falsifiable]].

Alternate hypotheses are that eukaryotic and prokaryotic cells were simply [[intelligent design|design]]ed as they are. This is, of course, like the endosymbiotic hypothesis, neither [[theory|testable]] nor [[falsifiable]].

[[Category:biology]]

[[Category:biology]]