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13-12-2003, 03:12 PM

In article ,
(Keith Michaels) wrote:
In article ,
(R.bioson) writes:
| I have seen many plants and other livingthings having their coiled
| body.
| many trees can have a right hand strand or a left hand strand form,
| just as they are forced to be that, but what caused them like that?
| I also find that in our universe there are so mang coiled forms, the
| typhoon, the clouds, the rocks, the stars groups and so on.
| Is it to say that the coiled form is mor stable than other forms?
| even I have been told that there are many right hand coiled forms
| than the left handed forms.
| but why?

A snail shell forms an exponential spiral because the direction of
new growth is proportional to all the growth that has come before.
If the growth direction is offset on the Z axis then it forms a helix,
or coil. Starting the helix in one direction (left or right) is
reinforced by subsequent growth. There is probably a predisposition
to handedness based on unit shape, and a randomizing component like
environment (temperature etc.) or a mutation that gets things going
in one direction or the other.

ISTR from lectures some decades ago that many organic molecules can
occur in two forms: "left handed" and "right handed" (the terms laevo
and dextro seem to ring a bell). Furthermore, the "natural" forms
(i.e. compounds created _in vivo_ rather than _in vitro_) all tend to
be of the same "rotation" [the distinction was originally made in
terms of the direction or "rotation" of refraction of light by the
two forms of compound, again IIRC].

I forget which was the common "natural" form (though I would vote for
"laevo" if forced to choose at this late stage) but it occurs to me
that such a fundamental feature of the building blocks of nature may
well result in a preponderance of of coils and spirals in the same
direction within species, if not more generally.

Cheers, Phred.

--
LID