steve_beats@hotmail.com

Is it true that the mechanism by which algae and diatoms "glide" is
still unknown? I've found a few papers that put forward theories, but
nothing that definitively states "this is it".

Through experimentation, I've established that several species simply
move towards brighter light, but I suspect the discovery of the
mechanism is beyond my amateur equipment (and abilities).

Cheers
Beats

Craven

<steve_beats@hotmail.com> wrote in message
news:1136890771.362729.53010@g49g2000cwa.googlegro ups.com...
> Is it true that the mechanism by which algae and diatoms "glide" is
> still unknown? I've found a few papers that put forward theories, but
> nothing that definitively states "this is it".
>
> Through experimentation, I've established that several species simply
> move towards brighter light, but I suspect the discovery of the
> mechanism is beyond my amateur equipment (and abilities).

Most scientific studies suggest theories and not PROOFS :-0

Craven

Tim Lamb

In message <dq06pj$m6n$1@news8.svr.pol.co.uk>, Craven
<crfishwick@hotmail.com> writes
>
><steve_beats@hotmail.com> wrote in message
>news:1136890771.362729.53010@g49g2000cwa.googlegr oups.com...
>> Is it true that the mechanism by which algae and diatoms "glide" is
>> still unknown? I've found a few papers that put forward theories, but
>> nothing that definitively states "this is it".
>>
>> Through experimentation, I've established that several species simply
>> move towards brighter light, but I suspect the discovery of the
>> mechanism is beyond my amateur equipment (and abilities).
>
>Most scientific studies suggest theories and not PROOFS :-0

Perhaps it is controlled *Brownian* motion. I imagine you could utilise
atomic particle nudges if you could reduce the amount of energy received
from the direction of desired travel.

How? Don't ask me, I'm a farmer:-)

regards

--
Tim Lamb

David Lee

Beats wrote in message...
> Is it true that the mechanism by which algae and diatoms "glide" is
> still unknown? I've found a few papers that put forward theories, but
> nothing that definitively states "this is it".
>
> Through experimentation, I've established that several species simply
> move towards brighter light, but I suspect the discovery of the
> mechanism is beyond my amateur equipment (and abilities).

All very confusing isn't it. Definitely associated with the raphe -
consensus seems to suggest that the mechanism is based on secretion of
mucilage from pores, which swells due to uptake of water and pushes the cell
along the substrate. Coupling between the mucilage and the cell seems to be
associated with fibrous structures along the raphe. However that's just my
reading and may not be the most recent definitive model.

It's great when you realise just how many "simple" facts are still
unexplained in nature! that's even true of British mammals. Our most
common species - the pipistrelle bats - virtually disappear in winter and
only a tiny proportion of the total population can be accounted for in known
hibernation sites! There are still plenty of things we can discover.
You're probably right that you would need some serious microscopy at very
least to contribute to the diatom locomotion mechanism but your light
experiments sound interesting and could well lead to publishable results!
The most important piece of amateur equipment is time - it's just as good as
the professional version but very much cheaper - so amateur naturalists can
sometimes achieve results that would be beyond the budget of a research
department!

David

David Lee

Craven wrote...
>
> Most scientific studies suggest theories and not PROOFS :-0

Most scientific studies TEST theories. TheorEMS have proofs - NOT theories.
Well designed experiments set out in an attempt to DISprove a theory and
once all reasonable objections have been shown to be invalid then the theory
can be accepted as correct beyond reasonable doubt. However you can never
claim an absolute proof since you cannot be sure that you have considered
every possible exception. Newton's theory of motion was tested and found to
be sound at every possible scale and was considered well and truly "proved"
until Michelson and Morley set the cat amongst the pigeons when they
demonstrated the constancy of the speed of light for all observers.

David

Triffid

David Lee wiffled:
> Craven wrote...
>>
>> Most scientific studies suggest theories and not PROOFS :-0
>
> Most scientific studies TEST theories. TheorEMS have proofs - NOT
> theories.

<troll>
So is it the TheoRUM of Evolution then?
</troll>

David Lee

Triffid wrote...
> <troll>
> So is it the TheoRUM of Evolution then?
> </troll>

Que? I may be getting dim in me old age but that one went straight over my
head!

David

Craven

"Triffid" <sodoff@btspamworld.com> wrote in message
news:43c41db0@212.67.96.135...
> David Lee wiffled:
>> Craven wrote...
>>>
>>> Most scientific studies suggest theories and not PROOFS :-0
>>
>> Most scientific studies TEST theories. TheorEMS have proofs - NOT
>> theories.
>
> <troll>
> So is it the TheoRUM of Evolution then?
> </troll>

To certain groups: Yes! Especially Americans ;-)

Mike Coon

Tim Lamb wrote:
> Perhaps it is controlled *Brownian* motion. I imagine you could
> utilise atomic particle nudges if you could reduce the amount of
> energy received from the direction of desired travel.


This can be looked up under the heading of "Maxwell's Demon".

Mike.
--
If reply address = connectfee, add an r because it is free not fee.

Triffid

David Lee wiffled:
> Triffid wrote...
>> <troll>
>> So is it the TheoRUM of Evolution then?
>> </troll>
>
> Que? I may be getting dim in me old age but that one went straight over
> my head!
>
> David

My suggestion was that the theory of evolution is generally accepted as
proved, although no absolute 'proof' has been advanced. Just because your
beak is different to mine does not prove that either of us are the future.
However it is a very contentious issue, hence the <troll>

David Lee

Triffid wrote...
> David Lee wiffled:
>> Triffid wrote...
>>> <troll>
>>> So is it the TheoRUM of Evolution then?
>>> </troll>
>>
>> Que? I may be getting dim in me old age but that one went straight over
>> my head!
>>
>> David
>
> My suggestion was that the theory of evolution is generally accepted as
> proved, although no absolute 'proof' has been advanced. Just because your
> beak is different to mine does not prove that either of us are the future.
> However it is a very contentious issue, hence the <troll>

Ah - simple as that - I was confused by your misspelling of theorem and
assumed that it must be some kind of pun!

However Trolls need feeding so...

My point was there can never be an absolute proof of ANY theory. However a
theory isn't just an unsubstantiated idea - that is an hypothesis. A theory
must be capable of making predictions and is tested by experiment or
observation to check that that nature behaves in the way that a model based
upon the theory will predict. The more independant experimental
observations that are in agreement with the theory the less the probability
of the theory being seriously incorrect. Newton's laws had been tested in
many ways over more than 200 years at scales ranging from atomic to galactic
and never found to fail, so the theory can be considered to have be
vindicated. The advent of the theory of relativity, at the beginning of the
20th century did not disprove Newton's theory but showed that it was
incomplete, with additional effects becoming significant only at relative
velocities approaching the speed of light.

In the same way, I am not aware of any evidence that seriously questions the
fundamentals of Darwin's theory that speciation is the result of the
selection of random changes on the basis of improved or degraded fitness.
We can see it happening at short timescales - the melanisation of the
peppered moth in highly polluted urban areas, the evolution of
pestcide-resistant "super-rats" and the mutation of viruses and bacteria to
produce dominant drug resistant strains are just three well known examples.

On the other hand "Creationism" and "Intelligent Design" are merely
hypotheses treated as axioms and do not have the status of theories. There
is never any attempt by proponents of the hypotheses to test them
experimentally or by observation and any serious discrepancies raised by
opponents on the basis of scientific observation or reasoning are generally
either ignored or explained by introducing additional hypothetical
parameters (such as the deliberate falsification of the fossil record by a
deity for some obscure purpose), rather than questioning the existing model.
It's very like the hypothesis of the geocentric universe - it was fine
whilst everything appeared to be rotating around the earth in concentric
spheres - however refined observation revealed serious anomalies such as
retrograde planetary motion - made even worse when planetary moons were also
observed. Because the basic religious tenet of the earth-centred universe
could not be questioned, more and more complex epicyclic motion had to be
postulated leading to a model that was contrived to the point of ridicule
and the whole edifice came tumbling down when Copernicus had the scientific
integrity to question the religious domination of independant scientific
thought and show that there was a much simpler and hence more likely
explanation.

David

Tim Lamb

In message <dq1dem$d69$1@news6.svr.pol.co.uk>, Mike Coon
<mjcoon@?.co.uk.invalid> writes
>Tim Lamb wrote:
>> Perhaps it is controlled *Brownian* motion. I imagine you could
>> utilise atomic particle nudges if you could reduce the amount of
>> energy received from the direction of desired travel.
>
>
>This can be looked up under the heading of "Maxwell's Demon".

I think Einstein had a go as well.

I guess a sphere would receive the same energy from all directions but
what happens if it could change shape or become partly reflective?

regards

--
Tim Lamb

David Lee

Tim Lamb wrote...
>>> Perhaps it is controlled *Brownian* motion. I imagine you could
>>> utilise atomic particle nudges if you could reduce the amount of
>>> energy received from the direction of desired travel.
>>
>>This can be looked up under the heading of "Maxwell's Demon".
>
> I think Einstein had a go as well.
>
> I guess a sphere would receive the same energy from all directions but
> what happens if it could change shape or become partly reflective?

AFAIK it's the pennate diatoms that move in this manner and mobility takes
place along a substrate and has been pretty conclusively related to the
raphe (longitudinal slit).

My understanding is that the process is believed to be caused by expansion
of exuded slime, as it absorbs water, pushing the cell forwards in the
direction of the raphe. However you could possibly make a viable case for
Brownian motion effects without recourse to any demon other than the
organism itself. On average, particle impacts due to Brownian motion would
tend to push the organism in all directions. However the cell is stuck to
the substrate by capillary action of its slime which confines its motion to
two dimensions and the linear nature of the raphe is likely to provide a
higher resistance to sideways motion. There are known to be micro-fibrous
structures associated with the raphe and you could argue that these act in
the same manner as skins on touring skis to prevent backwards movement.
Hence only particle impacts in the direction of intended motion would be
able to overcome the restraining forces and the cell would glide slowly
forwards.

Clearly you would need to carry out some detailed tribology studies and
calculations of the amount of energy available from Brownian collisions
before you could say whether this mechanism were feasible. However I'm
pretty sure that this isn't the basis of the effect - but then I'm no
expert.

David

Mike Coon

David Lee wrote:
> .... We can see it happening at short timescales - the
> melanisation of the peppered moth in highly polluted urban areas...

I think that that particular explanation (adjusted camouflage) has been
disproved, but I cannot remember how or whether an alternative explanation
has been advanced!

Mike.
--
If reply address = connectfee, add an r because it is free not fee.

David Lee

Mike Coon wrote...
>> .... We can see it happening at short timescales - the
>> melanisation of the peppered moth in highly polluted urban areas...
>
> I think that that particular explanation (adjusted camouflage) has been
> disproved, but I cannot remember how or whether an alternative explanation
> has been advanced!

No it hasn't been disproved and there hasn't been any alternative
explanation. The major 20th century study of the effect was carried out by
Bernard Kettlewell in the 1950s, when he carried out direct observations of
predation of moths from tree trunks and controlled mark-release-recapture
experiments in two populations in polluted and non-polluted oak woodlands.
He obtained strong evidence in support of support of the existing
differential predation model leading to dominance of the melanised form of
the moth. Kettlewell also demonstrated good correlation between the
frequency of melanic moths and high levels of sulphur dioxide and
atmospheric soot pollution. This correlation has since been reinforced by
observations that have demonstrated that as pollution levels have declined
as a result of clean-air legislation so has the frequency of melanic
Peppered moths.

There have been valid criticisms of Kettlewell's methodology (and that of
later workers) which, whilst they do not negate he conclusions, have been
seized on to cast doubt on the validity of the Peppered moth as a
demonstration of Dawinian selection. Most notable was an article by Robert
Matthews in that most respected peer reviewed journal the Sunday Telegraph
[14 March 1999]. Since then this has been seized on by creationists seeking
to undermine Darwin's theory and has been widely quoted on their websites.
However it seems that no scientist that has actually studied Peppered moths
is in any doubt but that melanisation of the species still stands as one of
the best examples of evolution by natural selection in action.

As far as I know not a single one of the very vocal opponents has any
experience at all of working with the species or most probably has ever even
seen a live Peppered moth in the wild.

A much fuller account can be found in Michael Majerus book "Moths" (New
Naturalist - still available at £19.99), in which he dedicates an entire
chapter of 37 pages (nearly 15% of the book) to the story of the melanic
Peppered moth. (Majerus is Reader in Evolution, Department of Genetics,
University of Cambridge so he should know what he is talking about!).

Whilst checking the availability of his book, I have also just come across a
detailed article by Majerus detailing with the entire saga and his own part
in it (from a talk he gave at the LSE two years ago), which seems to be well
worth reading, although so far I have only had time to scan it. See
http://www.gen.cam.ac.uk/Research/Ma...andisciple.doc with the slides
from his talk at http://www.gen.cam.ac.uk/Research/Ma...andisciple.ppt.

Majerus' conclusions are perhaps summed up in the two following extracts
from his powerpoint slides:

SUMMARY
* The case of the peppered moth provides irrefutable proof of biological
evolution through the process of natural selection. While there is strong
circumstantial evidence that differential bird predation is the main agent
of selection, the evidence is only circumstantial.

ENDNOTE
* Darwinian evolution does not stand or fall on the peppered moth case, but
in my view, the peppered moth is still one of the best examples of evolution
in action through natural selection.

* The critics of the peppered moth case should stick to topics they know
something about. Their creationist faiths belong in religious education
classes, not biology lessons.

David

Triffid

David Lee wiffled:
>
> * The critics of the peppered moth case should stick to topics they know
> something about. Their creationist faiths belong in religious education
> classes, not biology lessons.
>

I resent that. There is no reason at all that critisising Darwin implies
embedded cult religious views, and equally no reason that evolution itself
can't be decoupled from natural selection.

Those sodding moths have gone from white to black to white again in a couple
of decades, but people have been selectively breeding vaious animals for
many generations but have yet to succed in pulling an aquatic rabbit out of
the hat; moreover virually all domestic animals will revert to a natural
type in just a few generations.

Dragonflies are hundreds of millions of years old, but have still only
evolved into different dragonflies. Despite seeing off the absolute worst
that nature could throw at them, crocodiles have remained resolutely
crocodilian, and the odd mutant with wings or 3 jaws would probably have got
eaten.

So don't put YOUR belief up as a religion mister, it's as vulnerable as any
other faith.

David Lee

Triffid wrote...
> David Lee wiffled:
>>
>> * The critics of the peppered moth case should stick to topics they know
>> something about. Their creationist faiths belong in religious education
>> classes, not biology lessons.
>>
>
> I resent that. There is no reason at all that critisising Darwin implies
> embedded cult religious views, and equally no reason that evolution itself
> can't be decoupled from natural selection.
>
> Those sodding moths have gone from white to black to white again in a
> couple
> of decades, but people have been selectively breeding vaious animals for
> many generations but have yet to succed in pulling an aquatic rabbit out
> of
> the hat; moreover virually all domestic animals will revert to a natural
> type in just a few generations.
>
> Dragonflies are hundreds of millions of years old, but have still only
> evolved into different dragonflies. Despite seeing off the absolute worst
> that nature could throw at them, crocodiles have remained resolutely
> crocodilian, and the odd mutant with wings or 3 jaws would probably have
> got
> eaten.
>
> So don't put YOUR belief up as a religion mister, it's as vulnerable as
> any
> other faith.

Now hold your bloody horses and re-read my post before you shout at me! I
clearly stated that the extracts at the end were from Michael Majerus'
powerpoint slides. However, considering the way that he had been repeatedly
misquoted and had his own work twisted by the creationist lobby in an
attempt make it appear to support their case to dicredit Darwinian
evolution, I would say that he was remarkably restrained in his comments!
It's perfectly true that these critics apparently had no knowledge at all
about the subject that they were attempting to rubbish and so it's perfectly
reasonable to suggest that they should stick to what they know something
about.

As to critics not having "cult religious views" you should look to the
evidence in this case. A previous book by Michael Majerus - "Melanism:
Evolution in Action" (1988) was reviewed in "Nature" by Jerry A Coyne, in
which he was totally misquoted, with Coyne claiming that Majerus completely
denounced Kettlewell's studies on the Peppered moth and concluded that this
provided no evidence for Darwinian evolution. This bore absolutely no
resemblence to what Majerus had actually written and he has repeatedly
re-affirmed his conviction that the conclusions regarding the Peppered moth
as an example of evolution in action are sound. However inummerable
Creationist Christian organisations continue to quote Coynes review to this
day - frequently verbatim - as fraudulent evidence for Majerus'
anti-evolutionary views. His actual work is never referenced, indeed the
authors of this material never show any evidence of actually having read his
book.
I'm not prepared to wade through all this rubbish but three such Christian
group web pages from the top of the first screenful of Google hits are:
musf.org/pepperedmoths.html
http://www.biblicalcreation.org.uk/s...es/bcs101.html
www.christiankeys.ca/CreationNotes7.html

I'm not going to go through your arguments at this time - suffice it to say
that they are all non-issues that have been thoroughly dealt with many times
and explained within the framework of Darwinian evolution through naural
selection.

David

steve_beats@hotmail.com

> Those sodding moths have gone from white to black to white again in a couple
> of decades

Darwinian de-selection :-)

Harassed Dad

"Triffid" <sodoff@btspamworld.com> wrote in message
news:43c6c2ec@212.67.96.135...
>
> Dragonflies are hundreds of millions of years old, but have still only
> evolved into different dragonflies.

Did someone say dragonflies? Interestingly the evolution of dragonflies has
been extensively researched at a genetic level. Did you know for example
that the Common Blue Damselfly (Enallagma cyathegerum) seems to have spread
from an ancestor species originating near Japan? or that the Scandinavian
population is genetically distinct from the Spanish population, with the
Belgian/English populations seeming to carry individuals from both
genotypes. And that the species evolved since the end of the ice age -
spreading and mutating as the ice receeded. In America their are 38 species
of Enallagma, all descended from two original species who spread through the
US as the ice receeded, evolving into different species as they went. Not
only can we trace their descent we can even specify some of the genes that
changed.

This is why the Xtians desperate "it's only a theory" is so laughable - we
have good hard genetic evidence for descent from a common ancestor over a
whole host of species - and as time goes on we'll have even more.

http://www.journals.uchicago.edu/AN/...696/40696.html

is the reference for Enallagma

HarassedDad

Mike Coon

Triffid wrote:
> David Lee wiffled:
>>
>> * The critics of the peppered moth case should stick to topics they
>> know something about. Their creationist faiths belong in religious
>> education classes, not biology lessons.
>
> I resent that. There is no reason at all that critisising Darwin
> implies embedded cult religious views, and equally no reason that
> evolution itself can't be decoupled from natural selection.
> ...
> So don't put YOUR belief up as a religion mister, it's as vulnerable
> as any other faith.


I resent it too, but I'm with Dawkins in seeing religions as a dangerous
delusion and faith as an abdication of reason.

I knew the Torygraph was right-wing but still don't see it as creationist.
But then I don't read it (or any other newspaper).

Similarly I'm happy to have the peppered moth back with Darwin. Even if the
melanic form had always been present in small numbers and was not a variant
"invented" especially for newly-polluted environments, the change in
relative numbers is still Darwin in action even though not full speciation.

BTW crocodiles are certainly (still) crocodilian, but then so are
alligators.

Mike.
--
If reply address = connectfee, add an r because it is free not fee.