| bimmylee said: Endosymbiotic theory is far from foolproof. There is no way for Mitochondria to live outside of the cell. There is also no way to prove that they ever did. Stating similarities proves nothing. The burden of proof is on the one making the claim; in this case, it is you with the claim that Mitochondria were once their own cells. It is impossible to prove this, because there is no record of it ever happening; if you actually tried to test it, you would lose every time. If you have to make yourself feel better with cowardly attacks on one's level of education, of which you know nothing, then so be it. How big of you. |
A talking donkey told me it doesnt in a 2000+ year old book.
VS
Evidence that mitochondria and plastids arose from ancient endosymbiosis of bacteria is as follows.
- New mitochondria and plastids are formed only through a process similar to binary fission. In some algae, such as Euglena, the plastids can be destroyed by certain chemicals or prolonged absence of light without otherwise affecting the cell. In such a case, the plastids will not regenerate.
- They are surrounded by two or more membranes, and the innermost of these shows differences in composition from the other membranes of the cell. The composition is like that of a prokaryotic cell membrane.
- Both mitochondria and plastids contain DNA that is different from that of the cell nucleus and that is similar to that of bacteria (in being circular in shape and in its size).
- DNA sequence analysis and phylogenetic estimates suggests that nuclear DNA contains genes that probably came from plastids.
- These organelles' ribosomes are like those found in bacteria (70s).
- Proteins of organelle origin, like those of bacteria, use N-formylmethionine as the initiating amino acid.
- Much of the internal structure and biochemistry of plastids, for instance the presence of thylakoids and particular chlorophylls, is very similar to that of cyanobacteria. Phylogenetic estimates constructed with bacteria, plastids, and eukaryotic genomes also suggest that plastids are most closely related to cyanobacteria.
- Mitochondria have several enzymes and transport systems similar to those of prokaryotes.
- Some proteins encoded in the nucleus are transported to the organelle, and both mitochondria and plastids have small genomes compared to bacteria. This is consistent with an increased dependence on the eukaryotic host after forming an endosymbiosis. Most genes on the organellar genomes have been lost or moved to the nucleus. Most genes needed for mitochondrial and plastid function are located in the nucleus. Many originate from the bacterial endosymbiont.
- Plastids are present in very different groups of protists, some of which are closely related to forms lacking plastids. This suggests that if chloroplasts originated de novo, they did so multiple times, in which case their close similarity to each other is difficult to explain.
- Many of these protists contain "secondary" plastids that have been acquired from other plastid-containing eukaryotes, not from cyanobacteria directly.
- Among the eukaryotes that acquired their plastids directly from bacteria (known as Primoplantae), the glaucophyte algae have chloroplasts that strongly resemble cyanobacteria. In particular, they have a peptidoglycan cell wall between their two membranes.
- Mitochondria and plastids are just about the same size as bacteria.
http://en.wikipedia.org/wiki/Endosymbiotic_theory
