Viruses: alive or not?

[One Above All]

I wanted to know your opinions on this subject.

Long story short, viruses exhibit many of the same properties that "life" does, yet they don't belong in any eco-system[1] and can't reproduce (in the usual sense of the word). There are probably as many reasons for considering viruses to be alive as there are for considering them to be non-living.

1.	As far as I know.

[ParkingPlaces]

It has never made sense to me to say that viruses are not alive. They do stuff. Rocks don't. There should be some sort of differentiating label.

[Nick]

Depends.  Did Noah collect two of every kind for the Carnival cruise?

[mrbiscoop]

Viruses are an infectious biological agent. Whether they are considered alive or not is just semantics.

[jaimehlers]

I don't consider viruses alive.  They don't eat (not even to metabolize parts of the cells they hijack), for example (which is a key aspect of every other form of life).  They survive by hijacking a cell and using it to replicate themselves, rather than being able to reproduce using their own cell mechanisms (which is another key aspect of every other form of life).  Something that is missing two of the most important life functions really can't be considered 'alive'.

[Michal James]

*spammer deleted*

[screwtape]

I said "other".  I don't think it matters.  Alive is an arbitrary distinction at that point.

[Azdgari]

They are organic self-replicators.  This means they share with "living" things the most important trait of that category.  That said, I agree with Screwtape:  It's arbitrary.  Humans invented the word "alive" and assigned it a meaning.  We could have decided differently.  So what?

[mrbiscoop]

They are organic self-replicators.  This means they share with "living" things the most important trait of that category.  That said, I agree with Screwtape:  It's arbitrary.  Humans invented the word "alive" and assigned it a meaning.  We could have decided differently.  So what?

      They are not self replicators. Without co-opting a hosts DNA viruses are incapable of replication.

[relativetruth]

They are organic self-replicators.  This means they share with "living" things the most important trait of that category.  That said, I agree with Screwtape:  It's arbitrary.  Humans invented the word "alive" and assigned it a meaning.  We could have decided differently.  So what?

      They are not self replicators. Without co-opting a hosts DNA viruses are incapable of replication.

Elephant DNA cannot replicate until two elephants have sex. It cannot do it on its own.

Viruses just don't bother wasting their energy (indeed they use the hosts energy making mitochondria) to create a whole animal in order to replicate.

Anything that can cause itself to be replicated is a self replicator.

[shnozzola]

I said yes.  To think of it, the existence of viruses is just another excellent proof of evolution (and another reason to not suspect the existence of a perfectly omnipotent logical creator), and the niche that life finds.  It's just another offshoot of natural experimentation that has been successful.  IMO, quite beautifully demonstrates that there is no creator.


A devastating virus in some stone fruit species was in the news a few years ago - Plum Pox

http://www.aphis.usda.gov/plant_health/plant_pest_info/plum_pox/background.shtml

(This has been your atheist horticulture lesson for today.  )
  - my first attempt, that I deleted, was actually a fungus.   

[jaimehlers]

Elephant DNA cannot replicate until two elephants have sex. It cannot do it on its own.

Viruses just don't bother wasting their energy (indeed they use the hosts energy making mitochondria) to create a whole animal in order to replicate.

Anything that can cause itself to be replicated is a self replicator.

That's a bad example.  First off, elephant DNA does replicate on its own, whenever an elephant cell divides.  It happens lots and lots and lots of times during the life of an elephant.  Second, viruses don't have DNA in the first place.  They cannot divide like a true cell; they are not capable of self-replication.  They are capable of assisted replication, in that they can hijack a cell in order to make it produce copies of themselves.

I think of viruses as pseudolife - something that mimics some of the qualities of life without actually being truly alive.  Prions also fall into that category.

[Irish]

Ah, this question...

Yes, I do consider viruses to be alive because where I stand they fit all the properties of life.  That being said "life" is kind of a fuzzy concept.  Some things we consider to absolutely not be alive do share a few properties of life.  Some examples I've seen are stars, fire, and weather systems.

[Irish]

They survive by hijacking a cell and using it to replicate themselves, rather than being able to reproduce using their own cell mechanisms (which is another key aspect of every other form of life).

There are organisms that cannot freely replicate on their own but are still considered alive.  Chlamydia is an example.  They are obligate intracellular parasites, just like viruses, that cannot replicate outside of a host cell.

Second, viruses don't have DNA in the first place.

Some viruses do have DNA as their genetic material.  Viruses can have single stranded RNA or DNA, double stranded RNA or DNA, and both linear and circular varieties.  There's also some viruses with quasi-double stranded genomes.

[LoriPinkAngel]

I don't consider viruses alive.  They don't eat (not even to metabolize parts of the cells they hijack), for example (which is a key aspect of every other form of life).  They survive by hijacking a cell and using it to replicate themselves, rather than being able to reproduce using their own cell mechanisms (which is another key aspect of every other form of life).  Something that is missing two of the most important life functions really can't be considered 'alive'.

They also don't respirate.

[Fiji]

They're sort of the missing link between life and non-life. Whether you want to put them in the former or the latter or a new category is entirely arbitrary.

[Azdgari]

The acceptable degree to which something uses its own machinery, or borrows the machinery of its environment, for the purpose of self-replication is also kind of arbitrary, no?

[Mooby]

Nah, viruses aren't alive. They violate the Cell Theory and require cellular machinery of other organisms to carry out many of the functions of life. Same with prions and viroids.

[The Gawd]

this argument is just another way to divide organisms when we should be finding ways to unite...

[Mooby]

There's really no way to unite them, though. Viruses are basically rogue bits of subcellular machinery that mess up a cell's blueprint for how it's supposed to work.  If it does so in a way that makes more viruses, then evolution selects for it, but it's still a stretch to call that life.  It's just a piece of DNA or RNA and protein.

Compare to a viroid, which is just RNA, or a prion, which is just protein.  If a protein turns other protein into itself, is that protein suddenly an organism?  IMO it's just a rogue organic compound that stumbled into evolutionary selection by sheer accident.

[Truth OT]

Aren't we as humans just viruses on steriods that feed off of a host as other parasites do?

[wright]

  IMO it's just a rogue organic compound that stumbled into evolutionary selection by sheer accident.

Mooby, I'm honestly curious: you don't believe your god directs the evolutionary process?

[Mooby]

Actively? As in guiding individual mutations? No.