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Virus

About microscopic forms of life, including Bacteria, Archea, protozoans, algae and fungi. Topics relating to viruses, viroids and prions also belong here.

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Virus

Postby 2810712 » Thu Apr 07, 2005 7:43 am

When did viruses evolve, before or after the bacts, prots and fungs etc. ? ? ?

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Postby thank.darwin » Thu Apr 07, 2005 11:44 pm

We really don't know... they could have traveled to earth via asteroids...?
No amount of experimentation can ever prove me right; a single experiment can prove me wrong.
-Albert Einstein
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Postby biostudent84 » Thu Apr 07, 2005 11:47 pm

I think Canalon or Jelanen might be the best people to answer this question, so I moved it to the Microbiology forum. They check that area more :)
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Postby James » Fri Apr 08, 2005 1:08 am

Viruses need cells to invade to reproduce, therefore can't we conclude they must have 'evolved' after cellular life originated.
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Postby biostudent84 » Fri Apr 08, 2005 1:13 am

James wrote:Viruses need cells to invade to reproduce, therefore can't we conclude they must have 'evolved' after cellular life originated.


Unless Thank.Darwin's hypothesis is correct, yes you can. But even though it is unlikely that viruses came from outside this planet, we still cannot be totally sure.

Viruses use the exact same bases and amino acids that Terran life uses. While it is not impossible that extraterrestrial life could (some scientists say "must") create a genetic sequence and biochemistry, I find it hard to believe that it would be identical to ours.
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Postby canalon » Fri Apr 08, 2005 2:31 am

I do agree with James on this, parasites cannot evolve before their hots, then viruses probably evolved after some cellular life evolved first.

As for their extraterrestrial origin, I would just say that if you use Ockham Razor's, the answer is just that life appeared once on earth and viruses evolved from a cellular ancestor rather than to have to imagine a convergent evolution in space that would seed earth with viruses sharing the same basic mechanisms as the rest of earthly life forms (mostly DNA, RNA and genetic coding).

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Postby 2810712 » Fri Apr 08, 2005 10:51 am

I also, think that they can't evolve before cells originated. But, we cannot say surely that convergent evolution has not occured here, merely because it takes longer time.
Also, how can we explain their origin [ origin of viruses] on the basis of theory of mutation and natural selection.
Or their evolution was similar to the origin of life [origin of life for second time , but not entirely new life forms , some what new...] ???


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Postby canalon » Fri Apr 08, 2005 1:28 pm

2810712 wrote:I also, think that they can't evolve before cells originated. But, we cannot say surely that convergent evolution has not occured here, merely because it takes longer time.
Also, how can we explain their origin [ origin of viruses] on the basis of theory of mutation and natural selection.
Or their evolution was similar to the origin of life [origin of life for second time , but not entirely new life forms , some what new...] ???


Their origin can probably be explained by loss of functions due to a parasitic way of life. Quite extreme in its own way, but still start from the same basic chemistry. Convergent evolutions to explain why life will arise twice using exactly the same chemicals, the same coding and so on looks much less probable to me, don't you think?
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Postby biostudent84 » Fri Apr 08, 2005 1:58 pm

What side of the debate do you fall on, Patrick? Are viruses living organisms belonging to a sixth kingdom or not?
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Postby canalon » Fri Apr 08, 2005 3:52 pm

biostudent84 wrote:What side of the debate do you fall on, Patrick? Are viruses living organisms belonging to a sixth kingdom or not?


That they once were living organism is a sure thing for mem, are they still? I have really no idea if they could still be considered such though. But I still consider them as biological objects/beings.

Do they constitute a sixth kingdom? Well it would be interesting to know if all viruses emerged from a common ancestor, and then the answer would be yes, or if they are a case of convergent evolution of parasites, then I would have to say no. But tracing back their origins, when they lost so many of their original genetic material is probably impossible :roll:

So I stay in doubt and avoid definitive answers.

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Postby biostudent84 » Fri Apr 08, 2005 3:57 pm

Hmm. Does that mean it's possible, that they used to be organisms, but are no longer? Or does the long-held belief that all living things are made up of cells no longer apply?
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Postby canalon » Fri Apr 08, 2005 5:23 pm

Yes IMO they were organism and they lost everything non essential to be better parasites. Over simplifiaction like tape worm who lose its digestive tract. Or some mycobacteria that become endo parasites and can no longer be isolated outside of a cell.

The problem of living thing is mostly a question of definition. You can include them or not, as long as you give the definition you are using, so that anybody can understand you. I haven't made up my mind on this topic, that is all.

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