Protostome/ Deuterostome

[nikita]

Protostome/ Deuterostome

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Post by nikita » Mon Oct 13, 2008 1:24 am

Hi. I didnt really know where to put this, so I put it in general, as I thought more people would look in general. I am just having the hardest time finding out why deuterostomia is the more ancestral trait. I am thinking of possible essay answers and I am thinking of the Lophophorates and how they are a mixture of protostome and deuterostome traits. Apparently, protostomia is more derived, but why? any help would be appreciated.

[MichaelXY]

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Post by MichaelXY » Mon Oct 13, 2008 5:57 am

I would think a developing embryo would need to rid itself of waste first.

[alextemplet]

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Post by alextemplet » Mon Oct 13, 2008 6:05 pm

That makes sense, come to think of it, but I always thought protostomia was a more ancestral trait. Most of the simpler animals are protostomes, aren't they?

[nikita]

Re: Protostome/ Deuterostome

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Post by nikita » Mon Oct 13, 2008 6:24 pm

apparently, its a matter of debate. im trying to find a clear-cut answer, or at least information pointing in a direction of evidence for either, but im finding a lot of contradictory information. I would have thought protostomia was ancestral, but Im reading that the latest molecular studies are putting protostomes inside deuterostomes, ie.,
"Unfortunately, recent phylogenies, mostly molecular, rather put the kybosh on this view (Maddison, 2002). Deuterostomia is much lower down, probably the second branch of Bilateria to split off after the Acoelomorpha. Compared to its sister group, the omnipresent and spectacularly diverse Protostomia (containing the arthropods, molluscs and nematodes as its particular success stories), the deuterostomes are merely minor players." (http://www.palaeos.com/Invertebrates/De ... stomia.htm). i guess, since theyre molecular studies, i really dont have any developmental or phylogenetic proof, i guess i am just going to have to rely on the phrase "molecular studies."

[alextemplet]

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Post by alextemplet » Mon Oct 13, 2008 11:50 pm

Perhaps neither is ancestral to the other, and both are derived from the ancestors of the lophophorates. This could be possible given that the lophophorates share traits with both deuterostomes and protostomes.