Prokaryotes are primitive cells which lack a cell nucleus and membrane bound organelles. Archaea and bacteria are the two domains of pokaryotes. The genomes of prokaryotes are held within an irregular DNA/protein complex in the cytosol called the nucleoid. They reproduce by binary division or budding. One way of saying they make copies of themselves. This is an important distinction because reproduction via these methods does not allow for variation.
Eukaryotes are sophisticated cells with a nucleus and membrane bound organelles which have specialized functions. Nuclear material is held in the inner membrane of the cell nucleus. That material in turn produces complex proteins. Cell division is characteristic of complex process called nuclear division in which daughter cells receive a one copy of each chromosome. They also reproduce by sexual reproduction in which there are diploid generation in which two chromosomes are present, occurring through nuclear fusion and meiosis. The implication is eukaryote organisms can produce genetic variations which are healthy enough to both survive and possess the characteristics necessary to produce even more organisms – all of which vary slightly – but retain the same basic fundamental physical plan of the parent cells – they’re the same but different. The zen of evolution if you will. This advance in chromosome transfer and genetic variation allows for organisms to evolve. How did the mechanism for change occur if prokayrotic cells were the precursors of eukaryotic cells. As much as I’d like to avoid using the term – where is the missing link between these two types of cells. By no means the last word on the subject but biologists from Germany and Ireland may have found the mechanism by which eukaryote cells came about -
Thus, eukaryotes may be a mosaicism, combining features (including genes) inherited from a bacterial ancestor with those developed by an archaeal-eukaryotic ancestor before the split between eukaryotes and archaea. The hypotheses and debates about ancient cellular evolution continue as our knowledge of molecular and cellular mechanisms in all three domains of life expands (5). One intriguing curiosity is a “superphylum” of bacteria whose members display features of archaea and eukaryotes. What might these unusual organisms suggest in terms of evolution? It may be that their ancestor served as a “cauldron” for the evolution of eukaryotic and archaeal features, and that the superphylum is indicative of a path of intermediate steps between such an ancestor and an archaeal-eukaryotic ancestor (before the eventual split of the two domains).
Previously we had the “fusion hypotheses” in which two prokaryotes with enough difference in cell organization some how fused to leave a new organism with some of the attributes of a membrane bound cell with some kind of specialize if primitive components. These scientists have found a cell which lives in sewage treatment plants and acidic bogs with some qualities possessed by both prokaryotes and eukaryotes. These cells may be as old as prokaryotic cells. I do not think these disproves fusion theory so much as compliments it. These sewerage-bog organisms – PVC [Planctomycetes, Verrucomicrobiae, Chlamydiae] bacteria may have just been a dead end of many fusion incidents over billions of years.