05 Mar 08
please, don't come up with theological theories.
All life that ever existed on earth seems to be RNA-DNA based. This definitely evidences an original life from which all life forms evolved.
But imagining earth back then, I would say many different kinds of complex molecules aggregations could form. Why did only nucleic acid based ones survive?
If we could redo the experiment do you think nucleic acid based proto-organisms would be the dominant ones?
I think the ones that survived were the most unstable ones (propense to mutations). But I can imagine life forms whose building blocks wouldn't be C,N,O,H based.
Or CNOH based, but using very different mechanisms.
05 Mar 08
Originally posted by coquetteI would say there should be different kinds of life present, not protein based. (maybe not even CNOH based).
not only DNA "survived" and thrived, amino acids did too
but
DNA has one charming ability . . .it reproduces itself. that's a pretty important part of life
There are other unstable elements that can group spontaneously and interact. But everything is carbon based and even more difficult: protein based.
Is there such a greater competitive advantage of protein based life forms in this planet?
05 Mar 08
Originally posted by serigadoRegarding Life forms not made from C,N,O,H:
please, don't come up with theological theories.
All life that ever existed on earth seems to be RNA-DNA based. This definitely evidences an original life from which all life forms evolved.
But imagining earth back then, I would say many different kinds of complex molecules aggregations could form. Why did only nucleic acid based ones survive?
If we ...[text shortened]... ilding blocks wouldn't be C,N,O,H based.
Or CNOH based, but using very different mechanisms.
In order to be the building block of life (as we know it), an element needs the following (out of the top of my head, you might want many more attributes):
1. To be common.
2. To form bonds (Helium is out of the question! :-) ).
2a. Some of them will need the ability to form complex structures - thus, more then two bonds.
3. To form bonds that are both stable enough for complex structures to exist and not too hard to break so you could disassemble them.
4.To be able to form the basis for energetic reduction/oxidation reactions, in order to store and release energy.
5. To be able to form non-covalent bonds (all bonds referred to above are covalent).
05 Mar 08
Originally posted by serigadoConsider that abiogenesis is rare - it is very difficult to get life "off the ground" so to speak. It is very probable that no life form that uses something in the place of protein was there to compete with our ancient bacterial ancestors - And, if such a life form, one that uses something else instead of proteins, evolved after protein using life forms were already up and running, the new comers will probably be far behind the already complex and sophisticated "protein users", and will not be able to compete with them.
Is there such a greater competitive advantage of protein based life forms in this planet?
05 Mar 08
Originally posted by RetrovirusAgreed.
Regarding Life forms not made from C,N,O,H:
In order to be the building block of life (as we know it), an element needs the following (out of the top of my head, you might want many more attributes):
1. To be common.
2. To form bonds (Helium is out of the question! :-) ).
2a. Some of them will need the ability to form complex structures - thus, mo ...[text shortened]... se energy.
5. To be able to form non-covalent bonds (all bonds referred to above are covalent).
Just found this
http://en.wikipedia.org/wiki/Graham_Cairns-Smith
exactly what I was expecting. There might be some very simple and basic non-carbon based organisms, that would hardly survive.
But forgetting about non carbon life.... Why did life evolve exclusively with protein replicated organisms? There should be other mechanisms!
05 Mar 08
Originally posted by serigadoMutations aren't necessarily detrimental and damaging, some happened to be advantageous as well.
I think the ones that survived were the most unstable ones (propense to mutations).
Beauty of life is in its flexibility and adaptability to changing environment. Look at stable chemicals such as repetitive inorganic crystals.. what are they capable of? 😛
05 Mar 08
Originally posted by coquetteBut enzymes also guide which directions a particular molecule can follow. DNA alone would be highly unlikely to replicate since it has so many other 'choices' to follow, not least degradation.
enzymes make reactions go faster, they don't make reactions happen
05 Mar 08
1 edit
Originally posted by coquetteHaving nucleic acids only does not mean that "it" is capable of reproduction on the earth.
water (with heat, acid-base, and solvent properties), carbon chemistry (organic co-valent bonds), amino acids (building blocks for protein), necleic acids (for reproduction) and energy, and you will inevitably end up with a tax collector
(e.g. viruses cannot replicate independently without infecting a host cell to utilise its machinery)
Nucleic acids are just like a set of instructions. DNA is a master copy and RNA is a print-out for a short-term.
Don't tell me off for stating obvious...........
06 Mar 08
Originally posted by coquetteLOL, you can't be serious...
water (with heat, acid-base, and solvent properties), carbon chemistry (organic co-valent bonds), amino acids (building blocks for protein), necleic acids (for reproduction) and energy, and you will inevitably end up with a tax collector
06 Mar 08
Originally posted by znshoThat's were the "RNA world" hypothesis fits in.
But, does DNA reproduce itself? It needs enzymes to reproduce.
RNA can both store information (although DNA is better at it) AND catalyze reactions (although proteins are better at it).
http://en.wikipedia.org/wiki/RNA_world_hypothesis