If i was a molecular biologist, i would probably think it was absolutely clear that viruses are alive, because they contain a genome, and proteins encoded by the genome, and they use the proteins to make more copies of the genome. What else is life?
You could define biological life in a way that includes or excludes viruses, I would suggest, and be right either way.
(Also if a biological virus is alive, is a computer virus alive? It's self-replicating and has DNA in the form of code.)
Fundamentally life is a thermodynamic machine. Takes energy and converts a portion of it to 'work'.
Under homeostatic control. There are feedback systems that maintain the integrity of the organism.
In theory has a way of reproducing. This more applies to the species as a whole. Since individuals incapable of reproducing are none the less alive.
Viruses only meet the last and weaker criteria in my book.
Viruses are just replicators. Grey/Green/Brown/Bio goo. They are just dumb machines made by brute-forcing (fuzzing) more complex machines' immune systems.
Viruses might be a different branch on the RNA-replicator tree. Probably when the first replicators started some found - again via brute-forced mutations - that there are some replicators that they can take advantage of to replicate themselves.
And it just seems that closing this security hole is neigh impossible as long as we don't start to seriously tinker with that low level of "life" (eg. cellular machinery, transport, nucleus, messenger and transcription security).
One of the dominant theories for how eukaryotic organisms evolved (and by extension multicellular life) is by incorporating viruses and other prokaryotes internally and there's evidence a variety of viruses permanently entered the gene pool of several animals that were theoretically naturally selected for. It's less a branch and more a mobius rat's nest.
But that's no different how the rest of biology works. A parasite like Giardia is relatively just a dumb machine brute forcing itself through my immune system.
It's very likely an invariant of complexity. Trade offs (and friendly turtles) all the way. And of course evolution doesn't optimize for QALY at all. So it's not surprising that it hasn't really spent much resources on closing the gap. And now we try to do it because we do find it a better goal than "just" thriving in every imaginable niche on whatever complexity it's possible. (We want to maintain our complexity plus occupy more niches.)
https://en.wikipedia.org/wiki/Adeno-associated_virus#Infecti...
A virus needs a host like any parasite, without the host many parasites would not be able to reproduce.
To be pedantic, all you need is at most two (or three, maybe?) of the right gender to reproduce in a vacuum (metaphorically) to make it a living organism. A virus can't reproduce with another virus that way because it can't do anything on its own other than float around waiting for a host, no matter how many strains you mix it with. The host does the actual reproducing for the virus.
Cells can repeatedly produce certain proteins. For instance, a silkworm can spin out a thread of silk. That doesn't meant that molecules of silk are alive because they are reproducing.
Any parasite that requires its host for reproduction could be said to be a byproduct of the host continuing its biological functions usually at the expense of the host.
Nature draws no clear lines, humans apply taxonomy, any line we draw about what is alive and what isn't will be arbitrary.
My opinion is a virus is alive as it core process is based on how all life on earth operates through DNA/RNA. That is my arbitrary line, a distinct self contained genetic code that continues to replicate and evolve is alive. If that code can no longer continue replicating successfully it is dead.
Potassium cyanide can alter what happens in a cell; that doesn't mean potassium cyanide is alive.
Evolution/competition between ribosome encoding and capsid encoding organisms[1] has driven a lot of cool stuff to be developed: for example, bacteria and archaea (+ eukaryotes) gained DNA separately (presumably from viral infection) and retroviruses enables placentas.
It is tremendously difficult, perhaps impossible.
A chair is something you can sit on (but you can also sit on a rock)
&& it has a backrest (but the foot of a tree serves as a backrest)
&& it elevates you off the floor (but not all chairs take you above floor level very much)
&& it is manmade.
Eg, a chair is any object whose primary purpose is to sit a single individual
If it's meant to seat multiple people, it's a bench, a sofa, etc, but not a chair
If it's meant to be extra comfortable, it might be a single-seat sofa, but this itself a chair
If it's a rock, but positioned such that it's primary purpose is to sit an individual, such as next to a table, then it's a chair.
And most notably, primary purpose is subjective -- it might be understood as a chair, or as a doorstop, depending on your viewpoint, and what you use it for.
To sit an individual at close to, or at, a right angle in regards to their legs
A small rock versus a big rock; Approximating a squat, or standing, is out of bounds
But a stool may consistute a chair when sitting a child
Regardless, I'm mainly talking about the approach to defining it, and that definition by purpose rather than structure is more likely to find a correct definition, not that my example definition is sufficient
So is a zabuton[1] a chair?
It's a game you cannot win.
There are also ergo chairs that you "kneel" on instead!
EDIT: Addendum: It may also be worth asking what definition of truth you're using if we're going to be getting into philosophical arguments about what things are: https://en.wikipedia.org/wiki/Truth
1. A fish, and a flatworm.
2. The end parts of an anchor.
3. The fins on a whale's tail.
4. A stroke of luck.
The meanings are etymologically distinct (for the most part) and it's only chance they ended up wit the same spelling and pronunciation.
If that's philosophically troublesome, linguistics is not for you.
That is, when we refer to a word like “chair” we use quotes, but without the quotes, we can say that an accounting department chair is not a chair.
Alternatively, we could analyze “accounting department chair” as a use of metonymy.
Virions
Viroids
Satellites
Prions
Defective interfering particles (DIPs)
[0] https://en.wikipedia.org/wiki/Virus_classification#Subviral_...
> in the scientific communities
"Is it alive? <long property checklist> Yes/No" is an example of K-12 science education content diverging from science community practice. Both by emphasizing a little used concept, and by being inconsistent with community use.
With bonus points for it being... widely taught; taught as if it were science; an unnecessary hook for learning a set of properties; and an incoherently unfruitful predicate.
I don't know if there's a real name for such? I call them science-education-isms.
Google trends has data to 2004. "living nonliving"[1], aside from being a school-year detector, seems to show a 3x increase in the 2010's?
I'll also link [2], but I don't know what to make of it.
[1] https://trends.google.com/trends/explore?date=all&q=living%2... [2] https://books.google.com/ngrams/graph?content=living+and+non...
But it's a thin line, and it depends on which definition you want to use.
Or rather SARS-CoV-2 is the nonliving static code. COVID-19 is the “living” process interpreting the code.
Or your DNA is the code, you’re the living process interpreting that code.
The CPU, in this analogy, is physics.
We just got used to the DNA=life, but is this a valid assumption?
Some exotic lifeforms could encode their self-defining information on silicium magnetic polarisation, electron spin or whatever. And you would call them life if they were standing and moving in an animal-like way.
____
Tangentially related, I sympathize with Earth parasite Musk who wishes for us to infect another cell— err, I mean, planet. Shoosh, Earth, back to sleep, nothing to see here...
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[1]: I wonder who's the chicken, here. Certainly, the virus is the egg, right? It's all a plan to engineer the actual masters of this universe?
[2]: A long, long time ago...
[3]: Well, the 10% of my weight with my DNA. I feel more like an ecosystem, I am a legion of species, a myriad DNAs, we are millions in those guts. "I" is not even the same "I" when travelling to a different biome: you are what you eat, quite literally, however you want to spin that idea.
If viruses are on the edge of alive, then books and posters might be too, in some sense.
Virus's are "life" without replication machinery. And what is a book but a similar sort of dormant form, without the fertile replication machinery of the [human] mind to remix it and help its ideas fuck with other ideas. This view of viruses and words as life perhaps isn't as wrong as it first sounds, and some linguists on the fringes argue that language is more like a semiotic symbiont that has "moved into" our biology, specifically our neural structures, like a creature moving into an ecological niche and modifying it to suit its purposes. Or as I prefer to think about it: maybe we're already cyborgs straddling structures of biology and semiotics. (See: The Leiden School of Language[1]).
Maybe humans are just the first example of this language portion of our organism starting to venture cautiously outside of our biology, like astronauts exploring outside spaceship corpus ;) Reality might be pretty weird imho, and hard to see for what it truly is.
[1]: https://books.google.ca/books?hl=en&lr=&id=_ind5AbdQaAC&oi=f...
Maybe they actually are vastly superior to us and the hosts are just their air to breathe.
Therefore: The definition of life is "not eternal" (if you assume the law of excluded middle - actually the definition of "eternal" is "not life" :)
I always presumed that viruses, similar to other microorganisms, are alive. Until reading the above quote, I had never considered the idea there was any question about this. I was intrigued by the concept that they many not really be alive so looked up the Wikipedia article [1] which says that
> Viruses are considered by some to be a life form, because they carry genetic material, reproduce, and evolve through natural selection, although they lack key characteristics (such as cell structure) that are generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life", and as replicators.
One of the Wikipedia references is Are viruses alive? The replicator paradigm sheds decisive light on an old but misguided question [2] which looks at different replication mechanisms as a continuum rather than a simple “life vs non-life” dichotomy.
[1] https://en.wikipedia.org/wiki/Virus
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5406846/