CyberLegend aka Jure Sah
jure.sah at guest.arnes.si
Sun Oct 12 09:54:25 EST 2003
Tom Anderson wrote:
> On Thu, 2 Oct 2003, CyberLegend aka Jure Sah wrote:
> > I have heard such that the organels have evolved seperately and were
> > eventualy 'absorbed' into the cells and continued to live there.
> This theory is known as 'serial endosymbiosis', and it only applies to the
> mitochondrion and the chloroplast; some people suggest that eukaryotic
> cilia and flagella (aka undulipodia) are also derived from bacteria, but
> that is much less widely believed.
> - http://www.wikipedia.org/wiki/Endosymbiotic_hypothesis
> - http://www.geocities.com/jjmohn/endosymbiosis.htm
> - http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Endosymbiosis.html
Thank you very much.
> > I wonder how many hypotesys' are there that support the claim that the
> > organels have evolved in the cells themselves?
> That's an interesting question. I don't think there are any current
> hypotheses which explain the origin of the mitochondrion or chloroplast
> without reference to endosymbiosis. The killer evidence is that those
> organelles have their own genomes, which are more similar to bacterial
> than eukaryotic genomes; it's hard to see how such genomes could have
> developed inside a eukaryotic cell.
Yes indeed I did notice the genome inside of those as well, but it is
equaly hard to explain why a standalone cell (a standalone mitochondrion
for example) would have the function it has. Also given that the outer
membrane of the mitochondrion is of the cell that absorbed them, it
would be hard to imagine a natural environment loaded with H+ ions for
the standalone mitochondrion to use.
My idea of it is that eukaryotic cells had, like procaryonts,
free-floating circular DNA strands (procaryontic plasmids) that in their
time took care of the synthesys of ATP around the cell, which had
eventualy evolved into mitochondrion.
I guess the test would be to take a mitochondrion out of a cell and see
if it can survive and replicate.
I'm also very interested how does the endosymbiosis theory explain the
existantce other (non chloroplast) plastids.
Observer aka DustWolf aka CyberLegend aka Jure Sah
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