The endosymbiotic theory of eukaryotic evolution.

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The endosymbiotic theory was put forth for the first time by a Russian botanist Konstantin Mereschkowsky in 1905. The endosymbiotic theory of eukaryotic evolution was first postulated by former Boston University Biologist Lynn Margulis in 1967. The theory refers to the origin of Mitochondria and Plastids (Chloroplasts) which are basically the organelles of eukaryotic cells. The theory states that these organelles to start with originated as separate prokaryotic organisms but were taken into the cell as endosymbionts. Mitochondria developed from Proteobacteria (Rickettsiales) while chloroplasts developed from Cyanobacteria. According to Lynn Margulis, the eukaryotic cells originated as communities of interacting entities and included endosymbiotic spirochaetes that later developed into eukaryotic flagella and cilia. But this idea has not be accepted as flagella lack DNA and do not resemble the prokaryotes regarding their ultrastructure. According to Margulis, life evolved on earth through the process of networking or co-operation. However, some evolutionists have not accepted the endosymbiotic theory. The theory proposes that peroxisomes might have originated endosymbiotically, even though they lack DNA, but it seems that they have been formed afresh which is in contrast with the idea of symbiotic origin according to recent studies by Gabaldon et al., during 2006.

The evidences to prove that mitochondria and chloroplasts originated from the ancient endosymbiois of bacteria are as follows:
Both the organelles contain DNA which is different from that of the nucleus present in the cell but they are similar to that present in ...