Support for Prokaryotes....plz

[LunarStrain]

Sorry Guys...I never took high school bio and I dont know much, except that I find what little I do know extremely interesting now that I made it to university.

I searched my text book, net and forum after forum for info on the first cells. According to my text Prokaryotes were the first forms of life.

What I need help with is understanding the arguments for supporting them as the oldest microfossils (according to facts not faith)

Please....

[MrMistery]

Well it's like this
Prokaryotes are much simpler organisms than eukaryotes. They do not have a nucleus, nor do they have membrane bound organelles. It's common to state that the simple evolved first and then the more complex formes evolved.

Furthermore, we the endosymbiosis theory explains how eukaryotes first appeared: as a symbiosis between an archean and a bacteria.

Other than that, there is not much to say at first glance. Of course I could tell you about the differences between RNA polymerases and the discontinuous structure of DNA, but then you would be more confused than now.
So, if you have any more questions, a little bit more specific, i would happy to help.

[LunarStrain]

Your right that was a very general question. To be more specific, I have a couple of examples here in my book that I just dont understand. Maybe I'll start with one.

Living systems alter their environments, the most obvious change is that living systems are selective in the isotopes of carbon in compounds they use. Organisms incorporate carbon-12 into their cells before any other carbon isotope, and thus they can alter the ratios of these isotopes in the atmosphere. They also have a higher level of carbon-12 in their fossilized bodies than does the nonorganic rock around them.

So...that is what my book said...I dont really get it. Carbon signatures indicate carbon fixation, the incorporation of inorganic carbon into organic form??? What

[Darby]

If Life = cellular organisms, then prokaryotes almost have to be first by definition.

I think what you're having problems with is the idea that cell chemistry has a preference for certain carbon isotopes that aren't selected by geological processes the same way. If the ratios change toward the life-preferred isotopes, that's an indirect bit of evidence that the sediments that formed those layers, even if you can't find microfossils in them, had a lot of formerly living things in them.