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joozwa t1_irlx10b wrote

Reply to comment by Shadpool in What lifeform has the shortest genetic sequence? by teafuck

You seem to skim on the fact that living things also metabolize and viruses don't. Also - constant change in response to the environment can also happen in non-living things, eg. rivers.

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Poopster46 t1_irm6igv wrote

He didn't skim on it, he specifically said he considers viruses life. And as they don't metabolize, by his definition life does not require metabolism. At this point, there is no correct definition of what life is, there are just varying arguments to give for or against certain definitions.

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Shadpool t1_irlyr8w wrote

Viruses have no need to metabolize. They use the host’s guanosine/adenosine triphosphate to power itself. Environmental adaptations such as erosions by the river are passive changes, whereas the intake of ATP/GTP by the virus is active and deliberate.

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Algorythmis t1_irlyxef wrote

Do they power themselves though? Aren't there viruses that barely shove their RNA into the host and wait for things to happen?

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Cassius_Corodes t1_irmi8m0 wrote

I personally don't see it much different to eating an animal. You are just taking someone else's energy and materials and using it for your ends. I feel the divide is mostly due to our own bias to somehow see how we get our energy and materials as somehow more worthy.

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AedemHonoris t1_irnbnat wrote

Deliberately though. When an animal (collection of interworking and specialized eukaryotic cells) eats, it is doing so based on very specific chemical and physical signals. It's not that viruses are worthy, it's that they are aimless and directionless in their "existence". A prokaryote moving towards chemical signals and changing gene expression to consume nutrients to further purposefully divide is not the same a virus that happens to have the right configuration of proteins and genetic information to attach randomly to whatever has the correct antigen to allow for assimilation and replication.

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joozwa t1_irmlex1 wrote

Virus is a handful of molecules that in a certain environment tend to react physico-chemically as the chemical structure and properties of molecules dictate. If you deem it as an "active and deliberate" you'd have to consider every chemical reaction as active and deliberate. By this definition, a catalytic converter in your car is alive.

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AedemHonoris t1_irnay9e wrote

I think the biggest thing is viruses don't react to their environment in how prokaryotes and eukaryotes do. The latter can change gene expression to interact with their environment and even move deliberately (bacteria moving towards chemical signals and then changing membrane proteins to interact with their environment). Viruses just float around, like how atoms flow with little direction and can interact with what's around them the same as 2 hydrogen molecules can interact with an oxygen molecule.

I don't consider viruses or prions alive anymore than I do proteins or atoms.

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joozwa t1_irnisdx wrote

Indeed, there's much more going on in biological systems than just merely a replication. There's both anabolic and catabolic reactions, and compartmentalization allowing for these reactions in the first place. There are different receptors acting as an input signals that influence the aforementioned reactions. Viruses lack all of that, including arguably even replication, which they can't do by their own. There's not even any spectrum here - viruses don't have any biochemistry, and even the simplest bacteria or archea exhibit all of the processes mentioned.

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se_nicknehm t1_irmafq5 wrote

seems like viruses only have a highly specialized 'environment' they need to live in and have a very short individual lifespan

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Solesaver t1_irnox24 wrote

>They use the host’s...

No they don't. That would imply that they did something. A host encounters a virus and makes copies of it. The virus does nothing. We do everyone a disservice every time we imply a virus has any agency.

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Aspy343 t1_irmhipr wrote

>You seem to skim on the fact that living things also metabolize and viruses don't

That very much depends on how you define life though, doesn't it? Life isn't a "thing", it's a word definition made up by humans, and it can change. It's a bit like how there's no good definition of what a tree is, or if a bush counts.

Personally I'd say anything with DNA or RNA, that can replicate, is life.

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joozwa t1_irmkpl3 wrote

But viruses cannot replicate unless they're inside the cell. But you can say the same about just the nucleic acids. They cannot replicate - they're just a chemical molecules. Unless they're surrounded by a particular molecular machinery that allows them to replicate. By your definition RNA and DNA are alive.

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uber_snotling t1_irn2ae4 wrote

Yes, but every lifeform requires environmental conditions to be right to survive. Animals need oxygen. Plants need sunlight. Viruses need cells. Parasites need host organisms.

Most lifeforms will die if you put them in Antarctica or Jupiter or the Oort Cloud. That doesn't mean they won't thrive in the right environment.

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wintersdark t1_irn7ciu wrote

Just following his line of thought, the key difference is that viruses don't replicate. Viruses force other cellular machinery to replicate them. Parasites do replicate on their own, it's just that often they do that within other organisms but as you said - environmental requirements are normal for all life.

If viruses bred or replicated on their own within cells I'd agree, but that is not the case.

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uber_snotling t1_irn8jgr wrote

What about the Cordyceps fungus that infects insects and grows out of their heads? Or wasps that lay eggs in caterpillars or tarantulas to reproduce?

Replication requires conducive environmental conditions that may require other life forms. Life evolves to replicate within an environment - viruses are no different.

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wintersdark t1_irnw9fw wrote

No, there's a fundamental difference here. I wouldn't disagree if viruses could reproduce but only inside certain cells - would would be no different than parasites as you say.

That isn't what happens.

When cordyceps infects an ant, it controls the ant, and grows out of its head. Birds eat it, and it's spores end up in the bird's poop. Edit for more detail: cordyceps literally eats the ant's tissue, and uses that biomass to grow and produce the spores that will end up in the bird's poop.

The fungus requires the bird for its life cycle, but the fungus grows and produces spores on its own.

So what happens with viruses is that they cause the cell itself to produce more viruses. Viruses don't reproduce on their own at all regardless of environment.

This is specifically what makes viruses so weird and prompts questions about whether they are even alive, because they are the only organism that doesn't reproduce. They don't lay eggs, have babies, mate, reproduce asexually, eat, or even have a life cycle so to speak.

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the_red_scimitar t1_irnyrgv wrote

Yeah, but when it comes to not replicating, and needing another life form to do so.. sounds like an analog for sexual reproduction. Virus needs some of the mechanisms in another cell in order to produce. A human needs some of the mechanisms in the opposite sex in order to reproduce.

Sexual reproduction as such, it is not a requirement for life, it's just one of the most common ways life works here.

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wintersdark t1_irojqsf wrote

Sounds like maybe but isn't.

Two members of a species being required for reproduction is still reproduction done within a species. The new human is grown of the mother, with the input of the same species male's genetic code to ensure diversity. It's not like the human male slaps the females bottom, which causes her to suddenly start continuously producing human males over and over again until she dies.

Many creatures reproduce by simply dividing too, but in that case as well the new creature is literally made of the parent creature. They reproduce.

If you're looking at what's actually happening and not a stand-off analogy, the end result is:

  • Viruses do not eat
  • Viruses do not reproduce. Target cells do not just provide the environment for reproduction(we don't care about environments), they actually do the reproduction, not just host it. The new viruses are literally made entirely of and by the host creature's cells. Viruses neither seed, spore, divide, bud, lay eggs, or birth babies.
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Solesaver t1_irnqgbv wrote

Cars are alive. In the very specific environment of an automotive factory, the machinery and humans present replicate them from a base blueprint. /s

Viruses are not alive. They are merely particular arrangements of molecules that are prone to being replicated by a compatible host if encountered. The memetic conception of life (where any repeating or replicating pattern is "alive") is too degenerate to be usefully applied.

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inCogniJo14 t1_irnrjg4 wrote

In each time you've didn't to make a rebuttal, you are introducing different criteria on which life is defined. There are several criteria, and they are all a choice. That is the point that you are skimming over.

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AstariiFilms t1_irmjj2r wrote

By our current definition of life mules and other infertile hybrids are not alive as well. The definition needs to be revised. I'd propose that anything organic that reverses entropy is life.

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prairiepanda t1_irmp3za wrote

Infertile hybrids undergo cell division and are able to replicate their own cells; it is how they grow and heal wounds. Cellular reproduction does not necessarily mean generating offspring.

You couldn't consider infertile hybrids to be their own species because of their infertility, but that does not exclude them from qualifying as living things.

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Elrundir t1_irmwlag wrote

Fertility (i.e., the ability to reproduce to create an offspring that is likewise capable of doing the same) is a defining characteristic of a species, not a living thing.

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Solesaver t1_irntq38 wrote

Life is anything with the capacity for growth, reproduction, functional activity, and continual change preceding death.

While it's interesting to consider sterility as undermining the reproduction part, I think that's more an artifact of the taxonomy. It seems obvious that someone that happens to be born sterile is still alive, because this is more about describing a group than an individual. Humans are alive in a way that rocks are not. The sterile human is still a human, and as a group humans have the capacity for reproduction, even if an individual does not.

Now, all mules are sterile, but it is not a stretch to put the mule in the same taxonomy as its parents. That group clearly has the capacity to reproduce, they're the parents after all. The mule just has the misfortune of being born sterile.

One last semantic argument. The fact that we describe the mule as sterile actually reinforces the idea that it has the capacity for reproduction. It's just broken. If you take a bottle and drill holes in it, you could still talk about its capacity to hold water. It can't hold any water due to the holes, but that doesn't change its existence as a water vessel. You could print a whole batch of these, and they would still be water vessels, that happen to have their water holding be broken.

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