Re: Most Important Unsolved Problems?


<dougwedel@xxxxxxxxxxxxx> wrote in message news:dtmear$ckj$1@xxxxxxxxxxxxxxxxxxxxxx

"Perplexed in Peoria" <jimmenegay@xxxxxxxxxxxxx> wrote

Is there a larger question here of what drives life forms together into
larger more complex organizations? Think of the billions of separate
free-living organisms within your own body.

Well, I'm not sure that I see much commonality between symbiotic union
events (which probably occurred in the origin of the eukaryotes) and
the origin of multicellularity. One involves reciprocity, the other
involves 'kin selection'. As to 'what drives the cells together?' in
my body, I think that it is equally to the point to ask 'what drives
the cells apart?' in a culture of Paramecia.


I was talking not about the cells of your body but about the billions of
organisms from many different _species_ of microflora which live within your
body -- very similar to the idea of different species of free-living
bacteria joining forces to make the eukaryotic organism, is it not?

Ah yes. Sorry for misinterpreting.

Yes, all forms of mutualism have a lot in common. But there are some
important differences regarding the degree of integration between the
two organisms. The most important is whether the reproduction of the
small organism is only possible through the reproduction of the host.
Not the case for the E coli of my digestive system, nor the cellulose
digesting micro-organisms in the termite gut. These organisms can
be (and must be) transmitted 'horizontally' - from one termite to another.

Mitochondria and chloroplasts, by contrast, can only succeed if their
host succeeds, since the only way they can get to a new host is
through the host's eggs. That is a much deeper kind of union. And,
in the case of these organelles, the crucial step of an integrated
life cycle has been followed by even deeper integration - the partial
transfer of genomes. Most mitochondrial proteins (and many chloroplast
ones) are now encoded in the host nucleus.


.

Relevant Pages

  • Re: Most Important Unsolved Problems?
    ... free-living organisms within your own body. ... I'm not sure that I see much commonality between symbiotic union ... small organism is only possible through the reproduction of the host. ...
    (sci.bio.evolution)
  • Re: Intriguing new concept regarding human origins
    ... Other organisms move into those destroyed environments and live ... AFAIK, most if not all cases of organisms damaging ... It doesn't matter so long as the host species is numerous and able to replace the lost "resources". ...
    (talk.origins)
  • Re: Intriguing new concept regarding human origins
    ... Other organisms move into those destroyed environments and live ... It doesn't matter so long as the host species is numerous and able to replace the lost "resources". ...
    (talk.origins)
  • Re: Intriguing new concept regarding human origins
    ... Other organisms move into those destroyed environments and live ... It doesn't matter so long as the host species is numerous and able to replace ... Guns don't kill people; automobiles kill people. ...
    (talk.origins)
  • Re: Intriguing new concept regarding human origins
    ... Other organisms move into those destroyed environments and live ... It doesn't matter so long as the host species is numerous and able to replace the lost "resources". ... Because most lineages don't die out in a great extinction event, ...
    (talk.origins)