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NICHE541 · Guest

On Oct 1, 11:59=A0pm, "Entertained by my own EIMC Internetional Ptd.
Lty." <fell_spamtrap...@iinet.net.au> wrote:
[quote]"Tom Hendricks" <tom-hendri...@att.net> wrote in message

news:gb78m6$27uf$1@darwin.ediacara.org...

Blue green bacteria, cyanobacteria of today are almost identical to
billion year old fossils. "Approximately 90 species of fossilized
blue-green bacteria have contemporary look-alikes."
So why haven>t they changed.

"Tropical forests produce the largest number of species and rank first
worldwide in species diversity..." But what>s second? "... more plant
species are found in areas with big seasonal temperature fluctuations t=
han
in areas with more even climates... The plant survey suggests that the
tropics are biologically rich despite their even climates, not because =
of
them." So why have they diversified?*...... (Quotes from S. B. McGrayne=
)

I suggest my model of selection pressure explains both cases.

The greater the selection presssure , directional or diversifying
selection, the greater the speed of evolution.
AND
The lower the selection pressure, stabilizing selection, the lower the
speed of evolution.

In the case of bacteria the author says, "With this much success why
bother evolving". Thus low selection pressure leads to lower speed of
evolution.

In the case of the tropics and the areas with big seasonal temperatures=
,
both have high selection pressure on the species that live there -
tropics have high selection pressure from the vast numbers of competing
species,

You seem to be saying that: "As if life started to become diverse by bein=
g
thrown in to a bio-friendly locality where there were already vast number=
s
of competing species". :-\

and the big seasonal temperature fluctuations have high selection press=
ure
because of the demands of the temperature fluctuations.

Different temperature ranges offer different degrees of intrinsic and
extrinsic opportunities for life to form and flourish. ["Extrinsic
opportunites".~=3D different locality-dependent sets of environmental fac=
tors
affecting the fitness of "reproductive units".]

You are again trying to 'nail-down' how species arouse with 'a candle'. ;=
)- Hide quoted text -

- Show quoted text -
[/quote]

I really think you need some courses in Organic Chemistry I & II ,
Biochemistry and Comparative Physiology
John Hubbard

Tom Hendricks · Guest

On Oct 1, 11:59=A0pm, "Entertained by my own EIMC Internetional Ptd.
Lty." <fell_spamtrap...@iinet.net.au> wrote:
[quote]"Tom Hendricks" <tom-hendri...@att.net> wrote in message

news:gb78m6$27uf$1@darwin.ediacara.org...

Blue green bacteria, cyanobacteria of today are almost identical to
billion year old fossils. "Approximately 90 species of fossilized
blue-green bacteria have contemporary look-alikes."
So why haven>t they changed.

"Tropical forests produce the largest number of species and rank first
worldwide in species diversity..." But what>s second? "... more plant
species are found in areas with big seasonal temperature fluctuations t=
han
in areas with more even climates... The plant survey suggests that the
tropics are biologically rich despite their even climates, not because =
of
them." So why have they diversified?*...... (Quotes from S. B. McGrayne=
)

I suggest my model of selection pressure explains both cases.

The greater the selection presssure , directional or diversifying
selection, the greater the speed of evolution.
AND
The lower the selection pressure, stabilizing selection, the lower the
speed of evolution.

In the case of bacteria the author says, "With this much success why
bother evolving". Thus low selection pressure leads to lower speed of
evolution.

In the case of the tropics and the areas with big seasonal temperatures=
,
both have high selection pressure on the species that live there -
tropics have high selection pressure from the vast numbers of competing
species,

You seem to be saying that: "As if life started to become diverse by bein=
g
thrown in to a bio-friendly locality where there were already vast number=
s
of competing species". :-\
[/quote]
Nope didn>t mean to. There would not be the pressure that causes the
change.
I think it is the stress of competing species that speeds up the
evolution,
not the bio-friendly locality. That>s what the initial study said.
[quote]
and the big seasonal temperature fluctuations have high selection press=
ure
because of the demands of the temperature fluctuations.

Different temperature ranges offer different degrees of intrinsic and
extrinsic opportunities for life to form and flourish. ["Extrinsic
opportunites".~=3D different locality-dependent sets of environmental fac=
tors
affecting the fitness of "reproductive units".]

You are again trying to 'nail-down' how species arouse with 'a candle'. ;=
)[/quote]

Perplexed in Peoria · Guest

"Tim Tyler" <seemysig@googlemail.com> wrote in message news:gbtksm$jqq$1@darwin.ediacara.org...
[quote]On Sep 29, 5:59=A0am, "Perplexed in Peoria" <jimmene...@sbcglobal.net
wrote:
"Tim Tyler" <seemy...@googlemail.com> wrote:

Ouch. =A0What happens if the meteorite breaks up on entry, releasing
its payload as dust into the upper atmosphere?

Well, it is still going to have about the same peak velocity of 7.5+ km/s=
..

Surfing in the upper atmosphere you could slow down gradually.
As a small particle, you would lose heat quickly into the cold dark
reaches of space. With the right approach, you could probably
fall to the ground - and still land as a hailstone.
[/quote]
Sure, that is possible, though it is vanishingly unlikely that you would just
happen on the right angle-of-attack to permit this. But I think you have better
chances of arriving intact without overheating if you are one of many small
hailstone-size pebbles in the interior of a bigish comet which gets down to
an altitude of (say) 20,000 m before breaking up. Think Tunguska.

Lorentz · Guest

On Sep 22, 12:58=A0am, dterr...@hotmail.com wrote:
[quote]I read about the slime mold, which is actually not a mold but a "city"
of one-celled slime mold cells, each can separate and act
independently.

Can someone give me some other examples of this? =A0Of one-celled
lifeforms that act together as a swarm to do interesting/intelligent
things? =A0Some particular types of bacteria maybe? =A0Any and many
examples appreciated, thanks.
1) Myxobacteria[/quote]
2) Dinoflagellates
3) Biofilms
.....
Myxobacteria are a particularly good example. Myxobacteria form
multicellular structures including fruiting bodies. They are even
stranger than slime molds, but demonstrate that multicelluarity can
occur in different ways. Here>s a link that discusses myxobacteria as
well as other multicellular bacteria.
http://sandwalk.blogspot.com/2008/03/multicellular-bacteria.html
The link describes cyanobacteria, which I think weakens the point.
I think the cyanobacteria are in some ways a poor example, as they
"only" display filaments. Alot of single celled organisms, including
yeast and one celled algae, form filaments. However, I suspect
multicellularity starts from these humble beginnings.
Most single celled organisms have some type of social life. There
was a Scientific American article on social behavior in bacteria. I
hope you find it. Among other tidbits, the article showed dental
plaque with tubes where nutrients circulated.
When cultured on a Petri dish, almost all bacteria form
organized structures with at least some form of nongenetic
differentiation and specialization. By nongenetic, I mean the genome
of the different bacteria are almost the same while the gene
expression is different. The patterns are complex, but are often
specific to the species. Microbiologists can identify species by their
plate pattern without ever using a microscope to see the individual
bacteria. Sometimes, these structures form naturally in biofilms.
Dinoflagellates are protozoa (single-celled eukaryotes) that morph
into all sorts of forms. Some of these forms. Some of these forms are
predatory, and swim in formation after larger organisms such as fish.
Here, you have swarming behavior and differentiation. These guys seem
to be on their way to true multicellular, animal like behavior.

Entertained by my own EIM · Guest

A "piece of art" is (or ought, IMO, be approximately defined as) anything
perceivable that has been produced as a result of a creative urge and/or
ditto intention of an individual (or collaborative effort involving thusly
intending individuals).

Hence, any 'audio-visual' (audible and/or visible) mapping/representation of
scientific data that turn out to be emotionally or esthetically affecting
(possibly pleasing) DOES DEFINITELY NOT qualify as art - darn and dammit!
:-(

What I stupidity!

"Amir" <agiveon@gmail.com> wrote in message
news:gc1kek$2f3p$1@darwin.ediacara.org...
[quote]Have you ever seen a scientific related image and thought "wow, that>s
just beautiful!"?

I came across a couple of university internal "art of science"
competitions where scientists present images from their research and
compete based on beauty... why should it be only within universities?

I created a simple gallery at http://www.myartinscience.com/ where
anyone can post, view, share, comment and discuss these images.

Join me and share the beauty in science!

A.S
[/quote]

Ralf Muschall · Guest

On 30 Sep., 18:41, Tim Tyler <seemy...@googlemail.com> wrote:

[quote]As a small particle, you would lose heat quickly into the cold dark
reaches of space. With the right approach, you could probably
fall to the ground - and still land as a hailstone.
[/quote]
Maybe even without a special approach. IMHO the
problem with the mission was the fact that the heavy
vehicle at the back of the stone kept pushing at 7.5
km/s, thus cooking the stone thoroughly.
A lone stone would have lost speed quickly and
probably suffered only surface burns. At least
that>s what centimeter-sized meteorites or fragments
found on the ground look like.

Ralf

Lorentz · Guest

On Sep 16, 12:34=A0pm, Tom Hendricks <tom-hendri...@att.net> wrote:
[quote]This excerpt from MATCMadison,edu on absorbing UV light.http://matcmadiso=
n.edu/biotech/resources/methods/labManual/unit_4/exe...[/quote]
Yes, I think that the damage due to UV light on biological molecules
exerts a great deal of selective pressure on organisms that are
regularly exposed to UV light. However, I think that life could arise
in a world that never had any UV radiation.
[quote]
Proteins have two absorbance peaks in the UV region, one between >215-230=
nm, where peptide bonds absorb, and another at about 280 >nm due to light =[/quote]
absorption by aromatic amino acids (tyrosine, >tryptophan and phenylalanine=
).
The damage done by UV radiation is not solely determined by the
absorption spectra of biological molecules. The proteins are excellent
examples of materials where the damage done by electromagnetic
radiation is not solely determined by absorption spectra.
If UV light is absorbed by the peptide bond (215-230 nm), the
peptide bond will probably break. The peptide band is not stablized by
any electronic resonance. All protein molecules have an absorption
band between 215 and 230 nm. So any protein regardless of amino acid
content will be degraded by UV light between 215 and 230 nm. The
absorption by the peptide bond also results in very little
fluorescence or phosphorescence emission. The peptide bond falls apart
before the electron can emit photons or phonons. Sometimes the broken
bond forms a free radical, that can damage other molecules. So
absorption between 215 and 230 nm can be lethal.
In fact, any substance with a double bond is likely to
decompose when exposed to UV between 215 and 230 nm. Almost every
biological molecule has double bonds somewhere in it. So it is very
likely that the first living things evolved in the absence of UV
between 215 and 230 nm.
UV radiation between 215 and 230 nm could never reach the
surface of any planet with any reasonable atmosphere. I am not just
talking about ozone (i.e., triatomic oxygen). Diatomic oxygen and
diatomic nitrogen would absorb this radiation. Carbon dioxide would
absorb this radiation. Water vapor absorbs this type of radiation. I
can imagine a very thin atmosphere of methane, hydrogen and argon
letting through some of this radiation. However, I can>t imagine
anything under liquid water being exposed to this sort of radiation.
So we are left with a planet similar to Mars. If you have a mechanism
for abiogenesis applicable to the CURRENT conditions on Mars, then you
should contact NASA with this theory.
The absorption peak near 280 nm is not associated with
photodecomposition. Aromatic amino acids are associated both with the
peptide band and another band located in the benzyl ring. The benzyl
ring is very stable due to aromatic resonance. Thus, when the benzyl
ring is excited the aromatic bonds do not break. Much of the energy of
the excited electron either goes into fluorescence emission,
phosphorescence emission, or energy transfer to another nearby amino
acid. Very little absorption by the aromatic band results in a bond
breaking down. So the aromatic amino acids are very strong
fluorophores relative to other amino acids.
When a benzyl ring is excited in a protein molecule, it is very
likely to transfer its energy to another benzyl ring. When an aromatic
amino acid is excited in a protein molecule, the energy tends to jump
around. Amost all the energy absorbed by any of the three aromatic
amino acids (tryptophan, tyrosine, and phenylalanine) ends up in
tryptophan. Regardless of which aromatic amino acid absorbs light, it
is the tryptophan that eventually receives the energy. Therefore, if
absorption by UV radiation at 280 nm and shorter where important, the
tryptophan is the first to go. When that tryptophan is broken down,
the entire molecule is likely to stop working. Tryptophan is one of
the most common amino acids. It is in fact the main reason proteins
fluoresce. The emission band of proteins at 340 nm is primarily
tryptophan.
It is possible that tryptophan helps protect other amino acids in
the protein molecule from UV damage. However, one would expect
tryptophan to be at sites in the protein molecule which are not vital
to function. I never heard of such a preference.
[quote]Certain of the subunits of nucleic acids (purines) have an >absorbance max=
imum slightly below 260 nm while others >(pyrimidines) have a maximum sligh=[/quote]
tly above 260 nm. Therefore, >although it is common to say that the absorba=
nce peak of nucleic >acids is 260 nm, in reality, the absorbance maxima of =
different >fragments of DNA vary somewhat depending on their subunit >compo=
sition. "
Under current conditions on earth, UV at 260 nm doesn>t reach the
surface of the earth. It most certainly never reached the bottom of
the oceans. However, suppose it once did.
[quote]What if UV is a selective force at the start of life. If purines, and pyr=
imidines have slightly different absorbance maximums, then wouldn>t each ha=[/quote]
ve a selective advantage under certain UV conditions?
No. I can imagine a world without ozone (triatomic oxygen) where
the sunlight contains UV between 250 and 300 nm. I am basing this an
the cutoff frequency of diatomic oxygen, which starts at about 250 nm.
This spectrum is very broad. A small difference of say 5 nm won>t make
a significant selective difference. Every nucleotide and every amino
acid would be almost uniformly. An argument made for proteins also
applies to DNA. The energy, even if the difference were significant,
will go to the lowest energy nucleotide whatever that is. So
basically, the small differences in absorption spectrum won>t make a
difference.
[quote]
Thoughts?
Those are my thoughts. Don>t kill the messenger. I am just trying[/quote]
to help.

Lorentz · Guest

On Sep 26, 1:17=A0pm, Tom Hendricks <tom-hendri...@att.net> wrote:
[quote]On Sep 24, 12:18=3DA0pm, Alan Meyer <amey...@yahoo.com> wrote:

If purines and pyrimidines both have differences
two hydrogen bonds versus three
different UV absorbance
then that must account for some selection differences.
Only if the difference absorbance corresponded to different[/quote]
photodecomposition. Some chromophores can absorb radiation without
decomposition. The benzyl-ring chromophore in aromatic amino acids is
an example of a chromophore that absorbs UV without a corresponding
decomposition. I suspect that the pyradine-ring chromophore in
pyradines is the same way.
In many posts you repeat the assertion that
absorption=3Ddecomposition. This is not always true.
Also, you do realize that a lot of chemical environments break
down double bonds without UV radiation. In fact, some chemical
processes break down the double a lot better than UV absorption. The
differential selection that you ascribe to UV may be instead caused by
a high or low pH.
You also have this belief that the only seasonal change
possible are changes in UV irradiance. Seasonal cycles, even though
originating in the sun, express themselves in different ways. The
seasonal cycle could, for instance, cause an oscillation in pH. Even
if you think oscillations are necessary for abiogenesis, and I do not
believe so, the oscillations can be due to changes in the chemical
environment.
Maybe the surface where life started was near a beach, which was
periodically covered with salt water by the tide. A dry-salt water-dry
cycle twice a day. Or maybe once every 15 days, as happens wide
supertidal zones. Then the cycles would be associated with the moons
gravity. The cycle, if you need one, may not be solar at all. It
certainly doesn>t have to involve UV. It very well may involve solar
UV, but it doesn>t have to.

Lorentz · Guest

On Sep 24, 1:18=A0pm, Joachim Pimiskern <JoachimPimisk...@web.de> wrote:
[quote]dterr...@hotmail.com schrieb:

Another feat is the Pseudomonas quinolone signal. If times
get hard for the bacteria, they emit a chemical signal
named quinolone. Upon receiving this signal, some bacteria
commit suicide, setting free their DNA which is cannibalized
by the still living ones. This kind of bacterial sex enables
them to increase their diversity.
I think a gene centric model is probably an easier way to look[/quote]
at this process. The bacterial cells are not the level of selection
that provides the clearest explanation. For example, there is no
differential benefit to those bacterial cells that commit suicide. The
cells that commit suicide benefit all sorts of bacteria, not just the
species that emits quinolone. Since bacteria of a different species
are "enemies" of the bacteria that emit quinolone, it seems risky to
commit suicide in terms of survival of the quinolone emitting species.
So an "group selection model" may not be clear. Perhaps the following
gene centric model may be clearer.
Think of the bacterial cells that emit the quinolone as
vehicles for several different genes. The cells are like ships that
carry the genes from place to place, and the genes like sailors. When
times are good, it doesn>t take many sailors to run the ship.
The quinolone is more like a "hiring sailors" sign. There is a
network of genes in the bacterial cell that I will call the quinolone
network. When times are bad, this network switches on one gene that
tells the ribosomes to make quinolone. So I hypothesize their are also
suicide genes in the quinolone network that recognize the presence of
quinolone outside the cell.
The bacteria are not "committing suicide" to free their DNA for
other individuals. Rather, some of the genes in the bacterial cells
are ejecting from their vehicles (the cells). If other cells are
emitting quinolone, it means times must really be bad. The environment
must be getting bad for these bacteria. Similar genes in other
bacteria are directing their vehicles (their cells) to pick up the
survivors.
As far as the genes in the suicide cell are concerned, the other
bacteria are rescue vehicles. The quinolone indicates that the nearby
bacteria aren>t just going to digest the genes for energy.
Furthermore, the environment in the rescue vehicle is comfortable for
quinolone network genes. So the network genes may have a better chance
of surviving in a cell with other quinolone network genes than by
staying in one with a shortage of other genes.
Some of the genes will be picked up and incorporated into the
new vehicle. Furthermore, the cells that pick up the survivors get new
genes to work on their vehicle. The other gene may have a means of
fighting the hostile environment, or the other gene may increase the
risk of the vehicle being destroyed. However, there is a third
possibility. The new gene may be just a gene that helps emit quinolone
(i.e., part of the quinolone network). In which case, the quinolone
genes have helped one of their own.
The gene centric and the social selection descriptions may be on
some fundamental level equivalent. When trying to analyze how a social
behavior first evolves, I think the gene centric view is clearer. You
can>t talk about a "swarm" acting together until the swarm behavior is
already in place. Then, group selection may be a clearer way of
describing the further evolution of the swarm behavior.

John Edser · Guest

"Perplexed in Peoria" <jimmenegay@sbcglobal.net> wrote

[quote]"Tim Tyler":
A sequel to my 2002 essay - on the subject of living systems
maximising entropy production:
http://originoflife.net/gods_utility_function/

Tim, I>m afraid your logic isn>t very clear in this essay. You are discussing
"self organizing systems [in which the] rate of entropy production [is]
maximised. These were sometimes known as "dissipative structures" -
because they dissipated order, and produced disorder."

Close enough, but then you write: " ... a mechanism was found to explain
the phenomenon. At a low level, high- entropy states are more common
than lower entropy ones - so if a dynamical system changes in some
randomly selected way, it is likely to move into a higher-entropy state.
This simple principle drives systems of all kinds to rapidly move from
low-entropy states towards high-entropy ones."

Sorry, Tim. The mechanism you describe explains the 2LoT itself; i.e
it explains why *entropy* tends to be maximized.

It does nothing to explain why the *rate of entropy production* should
be maximized (and maximized only in *some* complex systems but
minimized in some other (slightly simpler) ones)
[/quote]
JE:-
Hi Jim,

Guy does interesting research in this field. What Tim may be getting at
is that non living systems only randomly form machines which
subsequently become naturally selected to maximize entropy increases per
associated unit. A simple whirlpool is produced via the objects
selectively configuring themselves to maximize entropy per associated
object within it. Living systems do the opposite: they are naturally
selected to configure themselves to maximize TDF: total Darwinian
fitness: the total number of strictly fertile forms reproduced per
parent per population. This locally maximizes a decrease in entropy via
of course, a general increase in entropy +outside+ of that particular
local entropy decrease. In short, non living systems form additive
groups of units of selection which mutualize increases in their entropy
as a non living fitness maximand for each associated object. OTOH,
living systems end up doing the opposite: they mutually maximize TDF per
associated unit of selection as a Total Darwinian Fitness maximand,
necessarily maximizing a reduction of entropy per unit in the process.

Regards,

John Edser
Independent Researcher

edser@ozemail.com.au

Steven Sullivan · Guest

dterrors@hotmail.com wrote:

[quote]I read about the slime mold, which is actually not a mold but a "city"
of one-celled slime mold cells, each can separate and act
independently.

Can someone give me some other examples of this? Of one-celled
lifeforms that act together as a swarm to do interesting/intelligent
things? Some particular types of bacteria maybe? Any and many
examples appreciated, thanks.
[/quote]

try this search on Pubmed:

'quorum sensing' AND review

--
-S
A wise man, therefore, proportions his belief to the evidence. -- David Hume, "On Miracles"
(1748)

John Edser · Guest

Lorentz <drosen0000@yahoo.com> wrote:

[quote]Joachim Pimiskern wrote:
Another feat is the Pseudomonas quinolone signal. If times
get hard for the bacteria, they emit a chemical signal
named quinolone. Upon receiving this signal, some bacteria
commit suicide, setting free their DNA which is cannibalized
by the still living ones. This kind of bacterial sex enables
them to increase their diversity.

I think a gene centric model is probably an easier way to look
at this process. The bacterial cells are not the level of selection
that provides the clearest explanation.
[/quote]
JE:-
This makes little sense to me. Bacterial cell GENE FITNESS was and
remains a nested (proper) subset of ONE cell bodies fitness (i.e. is not
just an intersecting gene centric fitness for genes within different
cells). Not one single gene has been empirically demonstrated to provide
an additive fitness per gene per genome per cell. This remains required
to empirically demonstrate any independent gene fitness from the cell
body within which each gene necessarily finds itself, _no matter how you
define fitness_. IOW, the popular gene centric view is not a theory of
anything, just a mathematical model (a polycentic, uncorrected
oversimplification of falsifiable moncentric Darwinism). I remind
readers that mathematics is not a science. This is only because
mathematics cannot define one, single, constant falsifiable frame of
reference. It was Galileo who firstly demonstrated that without such a
frame, everything remains relative to just nothing at all. Such
propositions typify Post Modernism which IMHO is destroying the sciences
like an epistemological cancer. Those interested may like to refer to
ongoing discussion within the group "critical rationalism":

http://www.geocities.com/criticalrationalist

[quote]For example, there is no
differential benefit to those bacterial cells that commit suicide.
[/quote]
JE:-
This is not necessarily true. For example, slime mold cells have been
shown to be selected at just the cell level (not the gene centric level)
to form optimally tall grouped cell fruiting bodies. The hight of the
fruiting body can be empirically demonstrated to provide a fitness
increase per cell per slime mold slug by increasing the mean dispersal
range available for all spores, *BUT AT A COST*. The benefit to every
cell taking part in this mutualized fitness strategy is a simple risk to
fitness ratio. To form the fruiting body some of the cells have to die
just to be able form the stalk which supports the fruiting body. If no
stalk is paid for via stiffened dead cells then the mean reproductive
fitness of EVERY cell decreases dramatically because their spores are
not sufficiently dispersed. If just some cells have to be sacrificed to
form the stiffened stalk then the random risk of being so employed can
be less than the reproductive gains as a cost benefit ratio, even if
total reproductive loss (death) is the risk involved.

Nature is providing a insurance premium provided by dividing up and
selling off risk pet cell per group at heavily reduced rates. Affordable
risk is selected for within nature but cannot be obtained for nothing.
In the slime mold situation, as soon as the risk to fitness ratio drops
below a certain point it is necessarily selected against because the
premium costs more than the gains in fitness.

The height of the slime mold fruiting body remains in a very sensitive
range. Just a little lower and the fitness loss for every fitness
mutualized cell decreases geometrically. If the fruiting body is too
high then the increase in premium (an increase in cell death
probability) becomes more than the fitness gains so it is selected
against. Cheating always fails because it inevitably reduces the optimal
fruiting body height and therefore, _the fitness of every cell_. The
sensitivity to fruiting body height is the key. Note that this does not
mean that cheating is not continuously attempted, it means that it is
continuously selected against. In this way so called "cheating" can be
view in quite a different light: a required source for heritable mutual
fitness variation.

Regards,

John Edser
Independent Researcher

edser@ozemail.com.au

Lorentz · Guest

On Oct 16, 12:50=A0pm, John Edser <ed...@ozemail.com.au> wrote:
[quote]Lorentz <drosen0...@yahoo.com> wrote:
...
Just a little lower and the fitness loss for every fitness
mutualized cell decreases geometrically. If the fruiting body is too
high then the increase in premium (an increase in cell death
probability) becomes more than the fitness gains so it is selected
against.
Except that when there is no "mutualized" cell when the fruiting[/quote]
body appears. The single cells when they come together become, well,
slime. The nuclear membranes have dissolved and the chromosomes are
all mixed together. Which means that the genes in a spore are probably
a mixture of genes from several of the original cells that came
together.
The concept of selection does not mean anything in terms of the
original cells that came together to form the slime mold. The genomes
of each original cell is destroyed. Only a few genes from each cell
survive in the spores that go in the fruiting bodies. The original
amoeba-like cells are gone: torn to pieces by the process that melds
together of the amoeba-like cells.
Your description makes sense in terms of genes. Each gene is
taking a "risk" by taking part in the process that produces the
fruiting body. A gene really does survive if it finds itself in a
fruiting body, even if it is the only gene from its original cell that
does survive. Thus, you description works if I replace the word "cell"
by gene.
This process by which a slime mold melds is analogous to the sex
other eukaryotes go through. Let me correct that. In all probability,
the process of melding is homologous to the sex other eukaryotes go
through. Slime mold amoeboid cells often have more than two distinct
sexes. One reason the joining together of multiple cells is useful is
that it increases the diversity of the genomes of the next generation.
The mixing up of genes follows meiosis and recombination in standard
sex. Splitting into amoeba-like cells followed by "slime" formation of
the slime mold results in mixing up genes. The important thing to
remember that in both cases, the individual cell NEVER survives the
process.
Sex in eukaryotes also ends up destroying the original cells as
well as the original genomes of the cells. The original cells NEVER
survive the mixing up of genes.
You keep on speaking about a unit of selection corresponding to
the most fertile stage of an individuals life. However, the processes
that we are talking about here ALWAYS destroys this unit of selection.
Aside from the difficulty in mathematical modeling, there is a
semantic problem in defining fitness in such a case.
I suppose with enough word smithing, one can fit the discussion to
a model involving the selection of an individual cell. I am not
arguing that there is one and only one way to look at natural
selection. However, I myself have a little problem visualizing a
differential selection with a unit of selection that is ALWAYS
destroyed each generation.

John Edser · Guest

dterrors@hotmail.com wrote:

[quote]I read about the slime mold, which is actually not a mold but a "city"
of one-celled slime mold cells, each can separate and act
independently.
Can someone give me some other examples of this? Of one-celled
lifeforms that act together as a swarm to do interesting/intelligent
things?
[/quote]
JE:-
The clearest example that I know of is provided by the slime molds. They
display mono-centric selection acting at just the individual cell level
(mono-centricity, meaning only ONE level of selection). In this example
the total number of adult (and thus _fertile_) slime mold cells
reproduced per parent per population provides a falsifiable fitness
maximand (a fitness which is always maximized). This refutable and thus
objective fitness measure should be contrasted to popular non
falsifiable, subjective, poly-centric models. Using any of these models,
whenever one level of selection stands falsified yet another level will
remains NON falsified making any theory based these models, non
falsifiable. The gene centric school popularized by Dawkins et al base
their argument on just uncorrected, oversimplified, non falsifiable,
poly-centric mathematical models of Darwinism within which TDF remains
deleted.

Mathematics is not a science simply because it cannot provide a single
frame of reference (as proven by Godel). This critical frame was firstly
introduced into the sciences by Galileo in the mid 1600>s. It was and
remains required to critically separate science from mathematics. A
falsifiable frame, is only implicitly provided within Darwinism as Total
Darwinian Fitness (TDF): the total number of strictly fertile forms
reproduced per parent per population. At all times TDF is naturally
selected to be maximized (hence the term "maximand" which was pioneered
by computer programmers).

I recently provided an outline of the slime mold example in my answer to
Lorentz.

Regards,

John Edser

John Edser · Guest

[quote]Edser>s response was a bit more interesting, and I will respond to his
suggestion here as well. John suggests that natural selection drives
each species toward maximizing its own entropy production.
[/quote]
JE:-
Hi Jim,
I think I stated that fertile (adult) individuals are selected in nature
to form reversible fitness mutualizing associations (populations) which
necessarily _minimizes_ entropy production per individual by maximizing
TDF (Total Darwinian Fitness) per associated Darwinian (mono-centric)
unit of selection, per population.

Regards,

John Edser
Independent


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