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Author Topic: Why Are All These Shells Orientated The Same Way ?  (Read 2010 times)

Offline neilep

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She sells sea shells by the sea shore.
And the shells she sells are surely sea shells.
Since she sells shells by the sea shore,
I'm sure the shells she sells are seashore shells.


Sheeesh !!

See THESE Sea Shells ?




Nice eh ?....notice how the orientation of the twist is the same in each shell ?...why's that then ?..and why that way and not the other ?...and why not a mixed bag of equal twistiness ?


Thanks


neil
Sea Shell Twisting Orientation Investigator









 

Offline RD

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Why Are All These Shells Orientated The Same Way ?
« Reply #1 on: 13/06/2008 21:15:08 »
Quote
The coil of a snail shell can be either right-handed (dextral) or left-handed (sinistral), based on whether the shell spirals out clockwise or counterclockwise when viewed from above. Most species are composed entirely of individuals that are one or the other type; in exceptional cases, populations may differ in their handedness, or chirality, but within a single population, all individuals tend to be alike. This makes sense, since the mechanics of reproduction are harder between two individuals of opposite chirality (their genitalia are also reversed), reducing the likelihood that they will successfully mate and produce offspring. Over time, therefore, the rarer type will become rarer and rarer until it goes extinct.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1182695

There's a screw joke in there somewhere :) .
 

Offline neilep

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Why Are All These Shells Orientated The Same Way ?
« Reply #2 on: 13/06/2008 21:15:45 »
Quote
The coil of a snail shell can be either right-handed (dextral) or left-handed (sinistral), based on whether the shell spirals out clockwise or counterclockwise when viewed from above. Most species are composed entirely of individuals that are one or the other type; in exceptional cases, populations may differ in their handedness, or chirality, but within a single population, all individuals tend to be alike. This makes sense, since the mechanics of reproduction are harder between two individuals of opposite chirality (their genitalia are also reversed), reducing the likelihood that they will successfully mate and produce offspring. Over time, therefore, the rarer type will become rarer and rarer until it goes extinct.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1182695

"reversed genetalia", that sounds painful  :) .



"reversed genetalia" ??...isn't that what girlies are ?  ::)


THANK EWE for this RD !...that's brilliant !!....but that's of course pertaining to a snail....what about seashells ?......(ewe've been really helpful today...ta chum)
 

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Why Are All These Shells Orientated The Same Way ?
« Reply #2 on: 13/06/2008 21:15:45 »

 

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