Joined: Oct. 2009
|Quote (dvunkannon @ Feb. 28 2011,11:56)|
|Quote (Alan Fox @ Feb. 28 2011,04:48)|
|I don't see the direct connection between the results discussed in the PDF and your two questions.|
I am (in my simplistic way) speculating whether Darwin's "warm little pond" even with tidal cycles and clay adhesion, is not such a good candidate for the development of the earliest life as, say, hydrothermal vents, with their juxtaposition of very hot and very cold water, turbulence and mixing, plenty of dissolved and deposited minerals, substrate for chemosynthetic reactions. I was wondering whether the paper I linked to might throw light on whether either environment is the more likely pathway. I guess as the Earth's early atmosphere was anoxic, the late expansion of genes involved in oxidation would be expected either way.
Sorry if this is not clear. I am talking of the domain, Archaea.
|Nick's main thesis is that eukaryotes respresent a merging of some bacteria and archaea that lived symbiotically until one became the mitochondria, triggering a whole series of profound changes leading to the eukaryote cell.|
Thanks for the recommend. Is this different from Lynn Margulis?
I think the study in the PDF actually cuts against the vent origin theories. Vent OOL relies on chemistry to provide the energy gradient that surface OOL is getting from the Sun. Wachtershauser's Iron-Sulfur World is an example. But according to the study, the genes for iron-sulfur and other kinds of chemistry don't show up until a few hundred million years after OOL -> RNA World -> cells -> LUCA. If vents are where OOL happened, my expectation is that genes for iron sulfur, etc chemistry would be old and ubiquitous. They are not.
Symbiotic, yes as Margulis has hypothesiszed about the mitochondria for a long time. Lane cites studies that X part of the eukaryote genome resembles bacterial, while Y part looks like archaea, where X and Y are groups of genes that hang together, functionally.
re: Woese, sure he's got lots of good things to say, but that essay in particular is the kind of ruminatory navel gazing I find cringe-worthy from elder statesman of science. Reductionism iz Teh Bad and sooo 19th Century. To be replaced by what, exactly, sensei?
He quotes Bohm:
|Nearly 40 years ago the physicist-philosopher David Bohm exposed the fundamental flaw in the mechanistic reductionist perspective (5): “It does seem odd… that just when physics is… moving away from mechanism, biology and psychology are moving closer to it. If the trend continues… scientists will be regarding living and intelligent beings as mechanical, while they suppose that inanimate matter is too complex and subtle to fit into the limited categories of mechanism.”|
Yeah, that's because biology falls into that range of sizes and range of forces where classical physics actually works. We don't need chaos, complexity, and quantum mechanics to explain 99% of biology. Deal with it.
He makes some good points in the middle of that essay about HGT and cellular evolution. But by talking about archaea and bacteria swapping genes for tRNA related functions he's showing that LUCA was before the translational machinery was locked down. Given these vast differences in core protein-genetic machinery, it is hard to see how bacteria came from archaea, instead of both coming from a very basic cell.
David, one point about the vent stuff.
(Again, this is my limited study of the subject, so take with salt and read more than just me)
The photosynthetic compounds have analogues in chemosynthetic organisms. Some of them seem to be more primitive versions in the CS organisms. If that is correct, then the equipment needed to take advantage of the sun, developed first in the CS organisms, then was coopted for photosynthesis.
Did I say this already?
Man, isn't cough syrup with codeine awesome?
Ignored by those who can't provide evidence for their claims.