John M,
I have a few, interspersed, comments. But,
first...I'm not sure what wording you are referring to
here:
John M. wrote: beware of wording, "All" their genes come
together from both parents, who, again came from 2 parents each, so not
counting crpssfertilization in 10 generations 1022 donors would be invlved -
not ONE commoner. Tis is a joke, but true.
The model 'ecosystem' is
cut to practicality. Stan Salthen replied to my rambling that "there is no
reproduction, because NONE of the involved TWO makes a perfect replica (unless
cloned)" that
it is not the individual, that replicates, but the
species.
In my research on mitochondrial DNA, I found several papers that
dealt with the fact that a cloned animal isn't really an exact replica because
the nucleus is the only part removed from the "host" egg cell, and is also the
only part transplanted from the cell of the animal to be cloned. So the
nuclear DNA is an exact replica, but the mitochondria are not. There is some
curiosity as to whether this is what is causing the problems (health related
and otherwise) in many cloned organisms.
I was fascinated by the statement that "it is not the individual
that replicates, but the species." I tend to disagree, because it is
individual changes that drive evolution, individual reproduction that
"creates" a species.
John M. wrote: Here I ask: "what is the species"? we have to establish a
pattern with allowances, like "a dog" either a chihuahua or a Dane, so a
species is also a limited, agreed-upon, cut model.
Unimaginably subtle are
the ways of reductionism!
A "species" is, ultimately, an
artificial label placing organisms in categories for the benefit of human
beings (be they scientists, farmers, Noah...). I think it is just human
nature to deal with the world via categories. Our brains seem to be pattern
seekers. Any difference we perceive in the pattern of some
category requires the creation of a new category. I agree that it's a
reductionist way of approaching the world but it works extremely well in many
situations.
Here's a few questions for the list: How do you suppose the first
living systems reproduced? What is the "most primitive" mode of reproduction?
At what point did "sexual reproduction" evolve-- i.e. do any species of single
celled organisms exchange genetic material during reproduction? What is the
possibility that the behavior of viruses became involved somehow in the
genesis of sexual reproduction in early organisms?
Judith
----- Original Message -----
From: Judith Rosen
To: ***
Sent: Tuesday, April 13, 2004 10:59
AM
Subject: Re: life as other than cellular/organismic
This has
been sitting in my drafts folder, awaiting some spare time:
> Dan
Fiscus posted:
> '"The naive picture that a group of organisms got all
their
> genes from a simple last common ancestor is breaking
down,"
> says microbiologist Gary Olsen of the University of Illinois
at
> Urbana-Champaign. In its place, the image of a
sophisticated,
> global community is emerging, he says. "In the past two
years,
> it feels like it's fallen together into a coherent picture."
Rather
> than a last common ancestor, LUCA may have been a last
>
common community.'
Ecosystems are slippery to define. For example; what
are the similarities and the differences between the concepts of "context",
"environment", "ecosystem", and "biosphere"? Secondly, when studying
biological systems, one must necessarily employ a reductionist technique, even
if only in the language with which to refer to ideas. Thus, a single organism
may be one that has only a single cell or it may be one that has billions of
cells. Let's say we want to study the single celled organism. If its
evolutionary context was the interior of a multicellular organism's body, then
that defines as the "ecosystem" something which would, under another context
of study, also be definable a single living system. It is well known
that multicellular organisms have served as the "ecosystems" for a whole mini
universe of organisms, some of them are parasitic, some are incidental, and
some are "beneficial", even necessary-- which makes them a
symbiotic/mutualistic organism. How does that happen...
It seems that
there are several ways to look at this. One, perhaps, would be to say that as
living systems evolved more complex organizations the notion of an ecosystem
was "internalized"-- within the organization-- every bit as much as the other
aspects of its context (as per the "anticipatory predictive model). On the
other hand, perhaps it is the nature of complexity to create relationships
within/inside and without/outside the organization of the complexity of a
multicellular organism, itself. Those relationships resemble one another in
certain ways. It's like those optical illusions where a drawing looks concave
one minute, then seems to change and looks convex... It's really both at the
same time, and neither.
The question I have is whether, before
organisms existed, there was any way for non-living systems to interact
in an "ecosystem"-- in the biological sense of that word. My definition
of ecosystem is such that the very "first" living system, by virtue of being a
living system, created the first ecosystem. It seems a near-certainty, to me,
that there were several "first living systems" popping up independently, all
at once. From each system's "perspective", all around it was "ecosystem" and
each living system exploited every functional opportunity that presented
itself.
It has been postulated that mitochondria were initially a
distinct living system, because they have their own genetic heritage, separate
from the nuclear genetic heritage of each cell. The functional benefits to
each "organism" made possible by co-existence conferred such advantages that
it continued. If that's how it happened, perhaps that was the moment the first
multicellular organism, in a sense, was
created.
Judith