Endosymbiotic Theory of Evolution of Eukaryotic Cells. Diagram of a chloroplast. Diagram of a mitochondrion. THE THEORY: The mitochondria and chloroplasts of Eukaryotic cells arose from the symbiotic incorporation of prokaryotic cells by a proto-eukaryotic cell.ukaryotic cells originated more than 0.6 billion years ago. The mitochondria (and plastids) of extant eukaryotic cells are remarkably similar suggesting aerobic bacteria (or cyanobacteria) were incorporated on only one occasion each.