Virus Evolution?

Question

A few months ago I asked this question about virus evolution. If Viruses evolve so fast, why are they still viruses? I mean, how come we don't see them evolving into some other kind of animal?

The response i got was that viruses are not even alive, but as i understand it, when evolution started way back when, animals got there start from nonliving material. So, why cant a non-living virus evolve into a living animal?

I thought the point of evolution was to evolve into something else. I mean, Fish-->Monkey-->Man type stuff. So if a virus is stuck being a virus, how is it that dinosaurs evolved into birds? Or is that apples and oranges?

I got various responses as to how it is not the point of evolution to simply evolve. What I understood from the replies is that there is no point. Regardless of whither there is a point to evolution or not people believe Fish-->Monkey-->Man type changes have accrued. So, if a virus is stuck being a virus, how is it that dinosaurs evolved into birds? Or is that apples and oranges?

These I added late and didnt get an answer for them.

Ok, the mechanism by which evolution is able to change one species into another is random mutations. Is this right? So, if the mutations are random, why cant a virus evolve an ability to survive outside of a host cell? I mean, Ive heard that creatures that lived under water evolved into creatures that can breathe air.

Also, do I understand it right that we don't know what viruses evolved from?

Answer 1

debate of virus being a live or not...
Argument continues over whether viruses are truly alive. According to the United States Code, they are considered micro-organisms in the sense of biological weaponry and malicious use. Scientists however are divided. They have no trouble classifying a horse as living, but things become complicated as they look at simple viruses, viroids and prions. Viruses resemble life in that they possess nucleic acid and can respond to their environment in a limited fashion. They can also reproduce by creating multiple copies of themselves through simple self-assembly.

Viruses do not have a cell structure, regarded as the basic unit of life. They are also absent from the fossil record, making phylogenic relationships difficult to determine. Additionally, although they reproduce, they do not metabolise on their own and therefore require a host cell to replicate and synthesise new products. However, bacterial species such as Rickettsia and Chlamydia, while living organisms, are also unable to reproduce outside of a host cell.

An argument can be made that all accepted forms of life use cell division to reproduce, whereas all viruses spontaneously assemble within cells. The comparison is drawn between viral self-assembly and the autonomous growth of non-living crystals. Virus self-assembly within host cells also has implications for the study of the origin of life, as it lends credence to the hypothesis that life could have started as self-assembling organic molecules.

If viruses are considered alive, then the criteria specifying life will have been permanently changed, leading scientists to question what the basic prerequisite of life is. If they are considered living then the prospect of creating artificial life is enhanced, or at least the standards required to call something artificially alive are reduced. If viruses were said to be alive, the question could follow of whether other even smaller infectious particles, such as viroids and prions, would next be considered forms of life.

Answer 2

I don't see how the question of whether viruses are "alive" or not is relevant to this question. They exhibit variation, they replicate with inheritance, therefore they are candidates for natural selection, therefore they can evolve ... and DO ... the fact that we need a new flu shot every year is precisely because viruses evolve.

Instead, here is the key point: You wrote: "I thought the point of evolution was to evolve into something else. "

Nope. You have to let go of that image that because A evolved into B once, that the point of evolution is to make A's evolve into B's.

It's not just that A's can just as easily evolve into C's next time.

But A's can be quite content to change into different forms of A's. If being an A (a virus) is a successul thing to be, then there is no reason it MUST turn into something else.

In other words, things evolve because they are pressured to do so. Not all members of a species or strain will feel the same pressure. It's possible that some undergo some environmental stress that causes them to evolve, while others of the same species or strain, do not undergo much pressure at all. So some will undergo radical evolution, while others stay pretty much the same ... for millions of years.

(P.S. ... I assumed you were joking about the "Fish-->Monkey-->Man type stuff" comment ... so I didn't address that particular mistake.)

Answer 3

You are right that evolution doesn't have a "point", in the sense that it doesn't follow some predetermined path or purpose. A given species is not necessarily going to have line of descendents that eventually include new species. Evolution does not say that fish will turn into monkeys and that monkeys will turn into humans. It shows that monkeys and humans had a common ancestor, and that along with fish (the first vertabrates) the three have a common ancestor even further back.

We can't say that a virus will evolve into a new species because technically viri are not organisms. They mutate and can be greatly affected by natural selection, but they don't have the same mechanics of heredity to make a "species", which makes it harder to define when exactly a virus has become a new "thing" all together.

Also, mutations, let alone "Random mutations", are not the only mechanism of evolution. It's also driven by natural selection (which is quite the opposite of "random chance") along with genetric drift, and other factors. Check out the links below to learn more.

Answer 4

You made an excellent point. Thank you, and I hope I am able to explain it for you.

It is a common misconception that people think viruses aren't alive because they are unable to reproduce on their own. There are infact to types of bacteria that are also unable to reproduce on their own. The reason viruses are not considered alive is that they lack the ability to create their own energy - they have no metabolitic actiivities.

They do not have this ability because they lack the genes required. To be able to create their own energy would require at least twice the number of genes they contain currently.

So if a virus infects a cell, and somehow ends up picking up the genes for metabolism from the cell, it now had a genome three times larger than before. This persents a problem. The size of the capsid. The protein coats of viruses are limited in size, and they simply could not get all the information inside the capsid. If the viral DNA/RNA tried to leave the cell without it, then
a. it would not longer be a virus, and
b. would probably be degraded pretty quickly.

So there you have it. It is a least one explanation.

E-mail me if you would like it explained in more detail.

Answer 5

The idea of evolution by natural selection is that some organisms have a higher chance of survival than others. Viruses are no different. Whether you consider them alive or not is irrelevant. They are prevalent because conditions dictate that they are prevalent. There is no intelligence involved.

Viruses probably evolved from simpler protein forms, such as prions. Viruses consist, in the main, of three or four different proteins, each acting as an outer shell, an inner core, grappling hook, or drill, to enter cells etc, plus a strand of DNA or RNA.
These may have originated as separate entities, but happen to come together, which increased the chances of survival, not by choice, but by having a better chance than those who were not joined together. Viruses do not evolve to survive outside a host cell because there is no pressure for them to do so. They have survived for millions of years quite well by doing what they do. Infecting other cells is efficient, since they do not have to have anything else to support, the host cell does it for them.

Answer 6

Well, as you can see, the answer is that they "mutate" but don't "evolve". This rather begs the question as to what the difference is. They both involve organisms giving rise to organisms with novel charactersitics and these novel charactersitics forming part of the characteristics passed onto future generations. The argument I have read is that the mutational changes are not enough to produce a new type of organism. And what is "type"? "Its still a virus" is quite true, but then an "ape" is still an "ape" - the creationist argument hasn't shown that Chimpanzees, Orangutans and Gorillas couldn't all have "mutated" from a common ancestor. And by extension they haven't shown that we haven't "mutated" from that same ancestor. If you draw the "mutation" boundary wide enough and all life could have "mutated" from the same primeaval sludge. The real answer is that the difference is purely linguistic. They do not like evolution but, with the mutations of micro-organisms, evolution is held up in front of their face. So they change the name.

Answer 7

Virii, evolve as they can. For instance, virii do not become insects. However, they evolve as virii and become more deadly, infecteous and so on. Why do they not become some other form of animal is just due to the way they evolve. Evolution of animals began with cellular structures and progressed from single celled animals to multi celled animals and so on. Virii, on the other hand, are not cellular organisms. They are RNA strands.

Answer 8

Gr8 Question.
as far as i know The evolution of virus doesn't manifest in the same mechanism by evolving in to another organism rather it results in adaptation of environment ( with high mutation rates) in the epidemiology of viral diseases such as influenza, HIV, hepatitis,etc