Re: Life's complexity: self-organization, evolution or both?

John Harshman wrote:

Bill Morse wrote:

r norman wrote:


On Mon, 17 Sep 2007 03:03:43 GMT, Bill Morse
<wdNOSPAmorse@xxxxxxxxxxxxxxxx> wrote:


Perplexed in Peoria wrote:



(snip)


That may well be true, but organism complexity and ecosystem
complexity are completely different animals. NS (i.e. reproduction
and genetic inheritance) is central in explaining organism complexity.
But NS isn't much involved in explaining ecosystem complexity.

Arguable. One doesn't ordinarily think of ecosystems as having excess
reproduction. But they might be considered to have heritable fitness. I
don't think one should completely dismiss the idea of ecosystems
competing.


Ecosystems are MUCH simpler than organisms, and their evolution is
something even a physicist can understand.

This seems extraordinarily unlikely on the face of it. Ecosystems are
composed of a large number of organisms. All our experience with other
systems tells us that aggregations of large numbers of subunits results
in greater complexity than that exhibited by any of the subunits.

It depends on how you count "number of subunits". Also, the patterns
of interaction between units within an organism are quite intense
whereas those between units within an ecosystem are rather weaker.
Yes, if somebody catches and eats you, that might be considered
intense from your point of view. But you have to look at the
population and the probability of being eaten. The nervous and
hormonal control systems, not to mention the genetic regulatory
control systems, within an organism and within a cell are much more
deterministic.


While I grant that there is a difference in intensity of interaction, the
definition is not all that clear. How does one treat endosymbionts? Are
they part of the larger organism or are they and the larger organism part
of a mini-ecosystem? And how does one treat eusocial insects, remembering
that ants comprise a huge fraction of the organisms in many terrestrial
ecosystems?

My initial thought in support of Pip's idea that ecosystems might be
simpler than organisms was that organisms in ecosystems might behave
statistically - I think this is in line with your argument that
interactions between units within an ecosystem are relatively weak. But
in reflecting on real ecosystems, I just don't see that statistical
methods capture much of what goes on. For instance,I'm unaware of any
statistical treatment that captures the importance of capstone species.



But without trying to measure complexity to see which one "wins", you
must consider that organisms must contribute to the success of the
ecosystem in which they live if they are to survive and reproduce. So
yes, indeed, ecosystems are strongly affected by evolution and change
with evolution. So why not just say that they evolve, even though the
mechanism is rather different from evolution of populations and
species.


I can agree with that. But I am interested in the question of whether
ecosystems also evolve by a mechanism that is similar to natural
selection. Do ecosystems compete? In the classic view of the 1960's that
I was taught, there was for instance a natural succession of ecosystems
following a disturbance. I doubt this is the current thinking. It seems
to me instead that succession as well as such phenomena as change in
vegetation mix with altitude on a given mountain can best be explained by
a model of competition between ecosystems.

That made no sense to me unless your last word was intended to be
"individuals" instead of "ecosystems". All succession would be is the
ability of different organisms to outcompete others in particular
environments over particular time scales, remembering that individuals
help create each others' environments. Succession is the statistical
result of all manner of individual interactions among species adapted to
different environmental features.

I am working on a hopefully more thoughtful response to your and Richards
comments. But in the meantime, exactly which "different organism" are you
referring to in the above. You, or your endosymbionts? Are you saying that
you (the individual) outcompete others but that your endosymbionts don't?
--
Yours, Bill Morse

.

Relevant Pages

  • Re: Lifes complexity: self-organization, evolution or both?
    ... and genetic inheritance) is central in explaining organism complexity. ... One doesn't ordinarily think of ecosystems as having excess ...
    (talk.origins)
  • Re: Lifes complexity: self-organization, evolution or both?
    ... complexity are completely different animals. ... I don't think one should completely dismiss the idea of ecosystems ... of interaction between units within an organism are quite intense ... It seems to me instead that succession as well as such ...
    (talk.origins)
  • Re: Lifes complexity: self-organization, evolution or both?
    ... complexity are completely different animals. ... I don't think one should completely dismiss the idea of ecosystems ... of interaction between units within an organism are quite intense ... there was for instance a natural succession of ecosystems ...
    (talk.origins)
  • Re: Lifes complexity: self-organization, evolution or both?
    ... and genetic inheritance) is central in explaining organism complexity. ... But NS isn't much involved in explaining ecosystem complexity. ... One doesn't ordinarily think of ecosystems as having excess ...
    (talk.origins)
  • Re: Lifes complexity: self-organization, evolution or both?
    ... I don't think one should completely dismiss the idea of ecosystems ... of interaction between units within an organism are quite intense ... statistical treatment that captures the importance of capstone species. ... there was for instance a natural succession of ecosystems ...
    (talk.origins)