Change is constant, no living fossils?

Discussion of everything related to the Theory of Evolution.

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mattw
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Change is constant, no living fossils?

Post by mattw » Fri Apr 27, 2007 5:54 pm

My question: biological clocks, such as small subunit RNA in ribosomes, and mitochondrial DNA, can measure geological time --and "distance" between related species, because over time they mutate at a predictable rate, right? Then how can we ever know the real genes of ancient organisms? How is DNA conserved somehow in "living fossils"?

Matt :)

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kotoreru
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Post by kotoreru » Fri Apr 27, 2007 7:05 pm

One can never 'know' what ancient DNA was like, only make decent guesses. Molecular clocks at the moment are in turmoil for a number of reasons anyway...
"What are humans if they don't learn at University? Animals, yes."

^^One of my ex-girlfriends said that. I stress the ex part.

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Post by Darby » Sat Apr 28, 2007 3:40 pm

Organisms often called "living fossils" are usually well-adapted to some microenvironment that has remained stable over long periods of time, such as horseshow crabs in surf environments, or pelagic sharks, or lots of tiny organisms. But all we know is that the physically resemble their ancestors - how much they may have changed chemically / genetically over time is harder to determine.

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Locus
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Post by Locus » Tue May 01, 2007 4:21 pm

Molecular clock based on the genes that do not changet it s spatial structure at the long time of evolution - thouse genes usially appier at the all organisms. Nevertheless, eve at the such genes it is almost impossible to say wich mutation is completly random, and wich not - becouse not only structure of the coded mollecule influenced by the mutation at the coding regions. (regulatory functions, chromatine fold...)
Evidence that molecular clock not very exact - at the different organism different rates of substitution finded!
Evolution will arrange everything

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mith
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Post by mith » Tue May 01, 2007 5:15 pm

pick bening mutations
Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
~Niebuhr

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