New Virus And The Origins Of Life

Discussion of everything related to the Theory of Evolution.

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alextemplet
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Post by alextemplet » Thu Mar 09, 2006 11:19 am

I say it sounds like you're saying exactly what Astus and I have said just with different wording. Viruses evolved from cellular life, not the other way around. Virus ancestors, for whatever reason, decided to live inside other cells and learned how to take over their DNA, endoparasitism. Over time viruses lost the ability to reproduce on their own. Viruses may have evolved from the first primordial life but can in no way be equivalent to it. It's like saying plant-eating animals can exist before plants.
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Post by damien james » Fri Mar 10, 2006 2:33 am

alextemplet wrote:Yes, we are learning new things every day, but how can it be possible for viruses to be precursors of life when they require fully-developed cells to survive?


In current form, virus needs other cell for life. But article says viruses may have shed genes that allow reproduction. Virus line may be original line of life still.

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Post by David George » Fri Mar 10, 2006 6:40 am

alextemplet

Mitachondria and chloroplasts are believed to be prokaryotes that lived symbiotically inside larger cells; it is believed that, after living inside other cells long enough, they lost the ability to live outside and became what we see today. Viruses could've been the exact same, except they harmed and destroyed their hosts rather than helped them. Or they could've been, as you said, random nucleotide sequences; however, given the extreme improbabilities of this, the first hypothesis seems by far the more plausible to me.


I think this hypothesis is different from mine because it says that virus came from a cell probably a bacterial cell but I say that the ancestors of virus were similar to virus rather than bacteria.I think this because viruses are very simple and so they must be primitive until it is the case of energy conservation.I can give you an example for energy conservation hypothesis.The example of a mexican fish that lives in the surface and mexican blind cave fish.Both these fishes live in the same waters infact they are almost same exept that one has eyes the other doesn't. Normal development of the eye occurs as nervous tissue, destined to become the retina, activates overlying tissue to form a lens. As the lens develops it directs the formation of a complete eye. In cave fish embryos the lens starts to form, but then degenerates and the eye does not form.

A team transplanted an embryonic surface-fish lens into a cave-fish embryo and, conversely, a degenerated lens from a cave-fish embryo into a surface-fish embryo. As expected, the surface fish with the transplanted cave fish lens did not develop eyes, but surprisingly, the cave fish with the transplanted lens from the surface fish developed large normal eyes. These results showed that, even after tens of thousands of years evolving in caves, most of the genes involved in eye formation in the cave-fish remained fully functional. Evidently a buildup of mutations in the eye genes had not occurred.

Further studies showed that cave-fish blindness is caused by a mutation in a master control gene. This gene switches on other genes during embryonic growth and is responsible for normal development of body regions. The mutated gene results in pleiotropic effects; it alters a number of features in the head, not only causing blindness, but also affecting teeth and taste buds. Fish with the mutated gene lack eyes and have more taste buds.

In a separate study of cave-fish cranial bones, it was discovered that these fish also have olfactory pits that are considerably larger than surface fish. Apparently a mutation in the same control gene that stops eye development in the fish also enhances its sense of smell. Natural selection is not acting on cave-fish eyes, instead it is selecting for the fish that can smell better and taste better, and these fish also become blind because the same gene affects all these traits. The light of Darwin’s theory of natural selection has been turned on in the cave.

In this example we can see different reasons why a fish doesn't need eyes in a cave one of the factors is also energy conservation because the eyes are lost energy is conserved but of course some is lost for the olfactory system.I know it does deviate from the topic but it is interesting.

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Post by alextemplet » Fri Mar 10, 2006 3:15 pm

That blind cave fish certainly is very interesting. I already knew about its eyes and its relation to surface-dwellers but I'd never studies it in that much detail. That said, I fail to see the relevance to viruses.

The ancestors of viruses, yes, might have been the origin of life. But actual viruses, no. No virus has ever been found that can survive without a living cell, not even this new mimivirus. All of your information about this virus is certainly interesting but it still tells us nothing about the origin of life as a whole.
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Post by David George » Sat Mar 11, 2006 5:13 am

Alex the reason why I say that viruses ancestors would have been the ancestors are because that virus are very simple forms they can evolve within months faster than bacteria this is the main reason a medice for SARS virus is hard to find.I think that the simple the organism the faster it evolves.

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Post by alextemplet » Sat Mar 11, 2006 5:10 pm

Yes, that is true, but I say again there is an important difference between viruses and the ancestors of viruses. Viruses cannot survive without cells and cannot be potential ancestors of life; the ancestors of viruses, however, might be, if any such evidence could be found.
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Post by David George » Sun Mar 12, 2006 5:43 am

I think that the ancestors of Virus would have been quite similar to the modern day virus exept that the mode of nutrition was different.It is like the ancestors feeding on chemicals that are non living and then evolving to feed on chemicals that are living.Probably the ancestors evolved wholely or became extinct.
"Nothing in biology makes sense except in the light of evolution"
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Post by alextemplet » Sun Mar 12, 2006 3:27 pm

So you're saying that viruses evolved from proto-cells rather than actual cells? I can accept that, as long as we understand that viruses themselves couldn't have evolved until after the cells they need to survive.
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Post by damien james » Mon Mar 13, 2006 5:10 am

If you are saying that main defining factor of virus is it depend on other cell for replication, then virus is not right term. But I believe virus shed self-replicating genes after adapting to other cells. It matters with new evidence how we should define virus now.
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Post by David George » Mon Mar 13, 2006 9:32 am

Looks like you are saying that viruses have only one item in their menu and those are cells.Well we cannot come to a conclusion that all viruse only feed on cells.If we find a new discovery it might change the whole mateer upside down.And I did say the ancestors of virus did feed on non living chemicals.
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Post by AstusAleator » Mon Mar 13, 2006 12:01 pm

I may be able to come to David's defence here.
I think he's saying that early virus-ancestors may have been cells that reproduced in a manner similar to bacterias' conjugation, in that they would insert their dna in another cell, and take that cells dna, prior to replication.

I'll then extrapolate that and say that perhaps this relationship evolved into a more complex endosymbiotic/parasitic relationship. Maybe they even had a lifecycle that involved living both inside and outside of a host.

If this be the case, then that type of cell may have given rise to both modern bacteria and viruses.

Having said all that, I've yet to see a convincing argument as to why viruses may have been the precursors to cells (viruses as we know them, not their hypothetical ancestors mentioned above).

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Post by alextemplet » Tue Mar 14, 2006 3:56 am

That sounds very reasonable, Astus, although like you said there's a huge lack of evidence when it comes to the origin of life, and viruses themselves certainly can't do anything to fill that gap.
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