Newsgroups: sci.environment

/ hpindda:sci.environment / gil@Gilsys.DIALix.oz.au (Gil Hardwick) / 12:21 am  Nov 14, 1992 /

I wrote:

>> My "abstract model" of ecosystem functions is just the idea of a hierarchy
>> of levels of biological organization, each level of which has emergent 
>> properties but is *constituitively* reducible to the level below it. There 
>> is little doubt that removing population-level functions very often degrades 
>> ecosystem level functions. E.g. removing species from a decomposer chain 
>> is likely to slow the rate at which nutrients are cycled, and also likely 
>> to increase nutrient losses from the system: those nutrients are liberated 
>> from detritus by the growth of *populations* of decomposer organisms. 
>> Likewise, the behavior of a population arises from the properties of the
>> organisms that make it up -- their individual tolerances and their chance 
>> encounters with varying conditions that are the day-to-day working of
>> natural selection.

Gil wrote:

>Offering an example has assisted considerably with communicating the
>idea you wish to impart, and I can follow most of what you have said
>here. Your "hierarchy of levels of biological organisation" is rather
>difficult to swallow since I have never experienced nature to be very
>well organised at all, much less hierarchical. Maybe you are simply
>borrowing the model from your own campus structure, or a bureaucracy
>somewhere which does indeed serve *functions* (albeit not without
>criticism) and imposing it as a convenience *you* deploy to organise
>your data.

"Hierarchy of levels of organization":

			biosphere
			ecosystems
			populations
			organisms
			organs
			tissues
			cells
			organelles
			molecules
			atoms
			quarks and leptons
			superstrings ???
Clearer?

>And I am having great difficulty with your *constituitively*. Where did
>you dig that one up, and what on earth does it mean?

I mean that each level is made out of the stuff of the level below it:
it is *constituted* of the stuff of that level. That is not necessarily
the same thing as *explanatory* reducibility, which would hold if every
*property* at level n could be explained entirely in terms of properties
at level n-1. This fails to hold in the biological levels at least because
some of the properties are "emergent" properties -- products of history 
which are *allowed* by, but in no way *required* by, the lower levels. 
[Physical scientists: think of boundary conditions.]

I.e., giraffes are certainly made up of quarks and leptons and obey all
the laws of physics but there is nothing in physics or chemistry which 
requires there to be giraffes: giraffes are productions of history. The
same thing is true of ecosystems and the processes which sustain them 
("functions").

>I have managed to discern to some extent who and what John McCarthy
>is, but still have no idea even who you are, or what you do. Perhaps
>"Alan McGowan" would like to introduce himself to the rest of the
>world, yes?

You mean you can't tell what to think of what I write unless you know "who 
I am"? Welcome to American-style democracy: I'm just another citizen with 
a mouth. That's the only requirement to post here. Don't forget that this
network is a tax-subsidized public forum in the U.S. I help to pay for it, 
and I damn well intend to use it -- and have my say in what it should be
used *for*.  When I first began posting in sci.environment, it seemed that
the only subject which was being discussed was nuclear power. There were 
almost no posts with any biological content. I wrote one wondering where
all the frogs are going and why more people weren't concerned about it. I
got e-mail saying, in effect, "well, that's just gee-whiz stuff, nuclear 
power (or chemical fertilizers, etc.) is where the Big Issues are at, so 
naturally that's what we discuss here." Right then I realized I had an 
ecocitizenly duty and some moderately grungy work to do. I'm still doing it. 

After all, *somebody* here has to stick up for frogs -- and as nobody
else appears able and willing, evidently it has to be me. My duty calls 
me in a resounding "ribbet, ribbet!"

>I keep wondering what there is about the environment which would prompt
>American biologists to refer to anything about it as central at all. Or
>are you referring only to American views of the world as being either
>"anthropocentric" or "ecocentric", perhaps derived from your cultural
>heritage, or your perception of your own country as being of central
>importance in world affairs, or something else?

The "central" in "ecocentric" and "anthropocentric" refers to position 
in a *value* system: some values are more "central" -- more deeply held
and defended -- than others. I believe the social psychologists have a
lot to say about this sort of thing. Cognitive dissonance theory or some 
such stuff. I strongly suspect that deeply held values arise at least 
in part from heritable traits of the limbic system, and are not exclusively
aqcuired characters, but that is another subject. 

>The definition of "healthy" you give here [ability to maintain adaptedness
--A.McG.]just about wipes out all the
>species adapted to very specific micro-climates, which cannot tolerate
>even small, transient environmental changes much less maintain their
>adaptiveness in the face of continuous environmental changes. 

Their metapopulations can maintain adaptedness if there are enough local
populations. Local extinctions are balanced on average by the formation 
of new populations -- otherwise the species would become extinct. 
Specific microenvironments occur in more than one place and can be colonized
or recolonized as conditions permit -- the species one finds in short-lived 
habitats are typically expert dispersers. Of course there are also species 
endemic to just one cave, etc.  Those *places* must have been pretty stable, 
or else those species wouldn't still exist.  

>I trust
>you are aware also that the vast majority of mutations are very much
>maladaptive, leaving risks associated with unplanned human intervention
>lacking expert consultation extremely high indeed.

The vast majority of mutations are silent or selectively neutral. Those that
are neither are usually deleterious and are rapidly removed from the
population. I'm not sure what "human interventions" Gil has in mind as
potentially increasing the mutation rate. Toxins, radioactive waste and
ozone depletion come to mind, and I can't imagine what "expert consultants"
one would consult about their proper use to increase mutation rates 
deliberately. Former EPA director Anne Gorsuch? Former Interior Secretary 
James Watt? Do they offer such consulting services?

Increasing the mutation rate is not quite what I have in mind when I talk 
about restoring diversity; the mutation rate is fine the way it is: we 
don't need more *production* of alleles, we need more *selection* for 
adaptive alleles, principly biotic selection, which takes habitat area 
and diversity on the ecosystem scale.

Incidently, mutations are far more common that most people realize -- 
on average each of us has about 11 random codon substitutions in our
nuclear DNA which were not present in our parents. Most of these 
substitutions are in non-coding passages or in non-critical parts of 
genes, or are silent because of the redundancy of the genetic code.

New alleles are in fact quite readily produced by populations. *Useful* 
new alleles -- that's another matter entirely. Those are products of 
natural selection, and natural selection results from opportunity, and
opportunity arises from numbers (habitat area) and diversity of other
life forms (biotic selection). 

The kind of natural selection that maintains adaptation is called "shaping
selection" for those who like to use the right terms. Maintaining adapation
is an ongoing affair, since there are forces which work to erode it. The
idea that adaptation is an equilibrium between shaping selection and the
erosive forces is known is the Red Queen Hypothesis (you have to run very
hard just to stay in the same place). Shaping selection takes arises from
habitat area and diversity, and when these are reduced too much, a species
can start to lose the Red Queen's race.

----------
Alan McGowen