I agree with CSF in thinking of plants and animals as similar, but I don't know about the 70% genome similarity thingy. The way I look at it, Eukaryotic cells originated and perhaps even started producing multicellular organisms, and somewhere down the track one line of these eukaryotes picked up a chloroplast. That was the beginning of the divergence of plants from animals. We still come from the same eukaryotic lineage, and that in itself means that originally we all had the same sorts of genome processes,
mitochondrial functions, ER, Golgi etc... We are very similar because the cell is the basic unit of life, and cells tend to be very similar in all life. While the way the cells come together vary drastically, they are all still very similar cells.
I am sure the cell wall etc are consequences of the gradual evolution towards adapting to their new method of survival.
Who says RNA was the starting material, later switching to DNA?
It is a very reasonable theory. RNA is afterall capable of acheiving everything DNA does, plus it catalyses its own copying (rRNA), its own translation (tRNA) and it is its own messenger (mRNA). In a haphazard system, it makes sense that RNA should hold its own code. DNA's only purpose is to stabilise the system into a double stranded system slightly less prone to nucleation.
Wolram, I have always thought that the deep sea hydrothermal vent idea was neat. It seemed a perfect condition for containing all of the necessary chemicals and the hot/cold alterations that can so assist the processes of life. (Do you know what PCR is? This is sort of how I imagine primordial life may have started). If you look around at the other threads in this forum though, and find Ivan Seekings post he has a link to an article that proposes it may have started in clay pools rather than deep sea vents though. I have no reason to really believe either yet, and of course more study is being done.
As for fossilization: No. Inverterbrates don't really fossilize...stromatalites are the only species I know of that have left behind traces of their existence, but that is a by-product of their existence (calcium piles i think?) not a fosilization of their actual bodies... Typically you need bones etc for fosilization to occur (and even then its incredibly hard to make it happen), and cells (or even worse: Proto cells) do not make the cut.
All life 'feeds on chemicals' to some extent or another
Animals eating plants, just like plants eating animals, just like bacteria eating bacteria is just part of nature. It always has been and always will be part of the natural system. The divergence between plants and animals would have been an evolutionary fluke, without any real significance at the time...As with basically all evolutionary divergences.
