Well then, are they or are they not?
I chose "other".
"alive" must first be defined to accurately reply to this question.
Do viruses have hereditary material? That is a common definition of "alive".
Yes exactly, what defines "alive".
Viruses are what they are. If alive is just being able to reproduce, then viruses are alive. If alive means consuming energy and being proactive (IE growth, movement) then nope, not alive
Often the debates about wether a virus is alive or not is really a debate about what constitutes "alive", without the participants even knowing it
Alive involves movement, metabolism and reproduction. One-celled animals like prokariotes do these things on their own. Viruses have no metabolism and their reproduction depends on the structures of the cells they prey upon. Some of them do move independently.
So I put NOT. The other category seems a cop-out; clearly even very simple bacteria are alive, and also clearly viruses don't do - independently - all the things a linving organism is assumed to.
What he said . . . no way.
It's a bit of programming that can take advantage of a living cell.
Some people have theorized that viruses were developed by some ancient form of bacteria as a weapon against other bacteria. I don't know the current scientific validity of that theory, but it makes sense. Something living (and with RNA at least) had to make the first virus, since it couldn't have made itself. If you don't believe that a bullet or a missile is alive, then neither is a virus.
You know they're alive after you've lived with a couple for a few years.
Of course, this assumtion would imply that all windows computers are alive. So that won't work dagit!
Interesting idea, sort of like venom. Looking at it on the constructive side, I have wondered if viruses might be genetic remnants left over from early single cell diversification.
if you can tell me a usefull purpose, reason for knowing i'll think about it.
otherwise, i don't care.
olde, it's interesting to see that the definition of "life" has some questions in it, contrqry to what might naively be presumed. It's always good to ground a high flying discussion in the real world, don't you think?
the world is full of impounderables. i'll invest time and energy with those that either expand my awareness or improve my life.
a pragmatic seeker? guilty!
"dead or alive"
Why not; is anything dead.
Or do things just change there physical states?
How much much more "dead or alive" is that oxigen molecule, that the "dead or alive" virus swallowed?
The question poses too much definition in terms, I suppose. No one here is going to agree 100% of what alive, dead, or neither actually consists and constitutes of.
There is general consensus that life is a self-sustaining sytem that metabolizes, multiplies, and has the ability to evolve. Because technically it can be said that a fire, for example, metabolizes and multiplies, I like the delimiter John Maynard Smith and Eors Szathmanry gave in their book "The Origins of Life." They said we might define as living ". . . any population of entities possessing those properties that are needed if the population is to evolve by natural selection. That is, entities are alive if they have the properties of multiplication, variation, and heredity (or are descended from such entities; a mule cannot multiply, but its parents did). . . . Why should we regard these three particular porperties as defining life? It is because they are necessary if a population is to evolve all the other characteristic we associate with life."
A virus, by even less of a definition than that, fails to show it is alive. Left on its own, it will not multipy, it will not variate (constructively), and of course it will not pass on genetic material. It can do nothing until it enters a living system, which then merely reproduces the virus and reacts to the virus. True, the virus can mutate, but it can only do that once it enters the living system. Remember, the genetic material of a virus came from formerly living cells, so we shouldn't be surprised that programmed into it is an adaptive trigger. Because a virus cannot mutate on its own, we have to assume it is the living system itself which is providing the impetus to pull that trigger.
A virus is not alive!
Viruses are biological uncertainty.
In biology, the only certainties are death and taxis.
Shh! Redefine the question, if you want, to include the phrase: According to your personal concept of life...
You see, I have a problem with this argument. Nothing does all the things a living organism is presumed to, independently. Plants need sunlight, for example. Humans need to eat. Animals usually need females, or males. Why can't we say that viruses are living carnivores, which feed on uninfected cells and digest them to function?
I think that virus must have de-evolved from a bacteria that was alive but for whatever reason became a parasite. How else could a virus come about or develop without life to make its DNA. It does not seem possible that it could be proto-life or a simpler form of life without more complex and complete life to prey on and to make its DNA or RNA whichever it is. Virus do adopt and become resistant but how they do this is a puzzle to me. How do they trick the host cell to change its RNA to overcome the host's defenses?
Actually, your examples easily fall into the categories of metabolism and reproduction, and so do not stray from "the things a living organism is presumed" to do independently.
We can say viruses "feed on uninfected cells and digest them to function," but so does a fire feed on wood, for instance, to function. Lots of things operate that way. That is why life requires more than just metabolism or reproduction to be defined properly.
The virus seems to me to operate exactly like programming does. Software just sits there until you insert it into the "living" (i.e., powered) system of a computer. What is the problem with differentiating between programming and the powered system?
Very funny Loren. I hate to encourage such pun-ishing contributions, but . . . how do you explain life's relentless, less-than-Checkered march toward adaptive-taxis while viruses are content to sit there "exempt" from change for eternity?
I'd say the virus is no more alive than the weather in the sense that it is a natural system. It really is an oddity of evolution in that way.
If you've ever seen that movie the Andromeda strain it shows how something can evolve without necessarily being alive.
Evolution is a completely natural process like the weather.
L W Sleeth
Think of the permanent stasis of viruses as occupying an otherwise unfulfilled niche. Also, not wasting energy on metabolism for processes like active motility can prove most efficient. One may thus think of a virus as utilizing statistically random currents to navigate its environment.
I agree. But, I heard viruses are more complicated than chemical molecules. Meaning, that it is much simplier than the most basic single cell organism. Virusues are very similar to organisms, viruses are made up of proteins and nucleic acid which are organic compounds. Some viruses have a lipid membrane, too. They evolve and mutate. A virus has the potential to reproduce with the aid of their host cell, but does not need energy to persist. So you can say it reproduces using another type of organism. Just like humans need "something else, a mate" to reproduce.
As I said, no one here is going to agree 100% on what life consists of exactly. So far.
In summation, I think you can safely say that [virusues] because they require the metabolic machinery of host cells to survive, and contain genetic material, you can say they both have living and nonliving characteristics.
The problem, obviously, is how we are going to define "alive."
We wouldn't have this debate about bacteria because it's clear they are a self-contained system which metabolizes, reproduces, and passes on hereditary information to their offspring. Even the primitive prokaryote has a huge range of metabolic patterns and is mobile, while viruses rely almost entirely on the enzymic machinery and metabolite supply of the hosts cells. As Gould put it, "Viruses certainly do not grow, and they feed only if we greatly expand our definition of feeding. In fact, they exist only because they can replicate . . ."
Everything I've read (which I have to rely on since I've not personally observed viruses, plasmids, or phages) gives me the impression viruses are zombies, soulless bits of capsid-bound RNA or DNA lacking any vitality whatsoever.
Using the words "soul" and "vitality" are controversial things to say, yet this debate might ultimately be about whether life is an inherent force or if it is merely the functions of chemical machinery. Some people want to call a virus alive because they are of the latter opinion, and of course some people of the former opinion don't see the virus as alive. So we are stuck at the point of defining what life is.
Personally, I can't even get myself to call a virus degenerate life. I think it is a dead piece of programming animated by living forms, and that to call it alive, we have to redefine what life has meant. If the science world gets to make that decision, and they decide to classify a virus as life, then I will still maintain in my own mind at least another category for beings which seem vitalized.
The thing is, the aspect of "aliveness" doesn't show up until a virus enters a host everyone agrees is "alive." Isn't that suspicious?
So, what most defines "aliveness"? Is it the machinery of a biological form or is it the dynamism? Even the simple, organelle-less prokayote exhibits dynamism. In fact, when we observe a "dead" thing, we see all the machinery is present, but it has lost its dynamic-ness. Even if we agree that it's the machinery alone which produces that dynamism, it's loss nonetheless makes the thing dead (and a living being's dynamism can endure through the failure or loss of a great many machine parts too).
That's why I can't see what to make of the lack of dynamism in a virus except that it isn't alive itself, and is only animated by something that is alive. I suppose someone might argue that the virus is made alive by its host, but to me then we have to include my bicycle as alive while I ride it.
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