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Mollusks

Postby fran008 » Thu Nov 03, 2005 5:06 pm

Why mightmollusks not have evolved segmentation, given that a segmented body enables improved control over locomotion?
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Postby iri_black » Fri Nov 04, 2005 8:04 am

What are mightmollusks? :? :? :?
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Postby mith » Fri Nov 04, 2005 12:53 pm

Translation for romanians :)

why might mollusks.....
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Postby MrMistery » Fri Nov 04, 2005 7:16 pm

Thanks for that Dave. I hadn't caught it either.
Now, mollusks are one of the oldest groupes of organisms that exists, even older than tubular worms it seems. They did develop body segmentation, by speciation, which resulted into arthropods. But since they almost never had the same applied niche they did not dissapear
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Postby Beetle » Sun Nov 06, 2005 2:01 pm

Some say that they lose their segmentation due to their specific locomotor organ - foot wich doesn`t need segments for it`s function.
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Postby MrMistery » Sun Nov 06, 2005 5:32 pm

Are you saying that mollusks had a segmented body once? Could be, i guess the real way of knowing is to go back in time... :D
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Postby Beetle » Mon Nov 07, 2005 11:45 pm

Well I`m just telling you what i`ve been told. I`m not interested in this group so I can`t say much more. Many argue what is source group of moluscs. Some say that Monoplachophora are the first to become because of their primitiv morphology. Others that Monoplachophora are just specialized highly evlolved group distant from other groups. They sey that origin group are Polylachophora wich have some segmentated systems. Or some say that recent gorups evolved each in it`s own evolutionary line. Who can say :?: :? Why aren`t those physicists doing something pragmatic like inventing time machine and save us biologists from tapping in the twilight of todays evolutionary science? But I gess that wouldn`t be fun then. :wink:
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Postby MrMistery » Tue Nov 08, 2005 8:34 pm

That is funny since i have been told that the heart actually appeared for the first time at mollusks in the animal kingdom since they are phylogenetically older than tubular worms...
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Postby Beetle » Mon Nov 14, 2005 11:23 pm

Unfortunatly during my studies no one gave me satisfing picture (or almost any picture) of cambrian explosion and the origin of the todays phylums so I cannot argue about that. :( :?
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Postby MrMistery » Tue Nov 15, 2005 8:48 pm

Pictures taken in the cambrian? I guess they should be pretty blurry since cameras were primitive back then :) :)
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Postby Beetle » Sun Nov 20, 2005 11:17 pm

Yes, and a photographer unffortunately died cause of an explosion. :)
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