Defining Life: The Debate Over Whether Viruses Qualify

[SpaceGuy50]

Are viruses life?

 

[Ygggdrasil]

It depends on how you define life (which surprisingly is not very well defined).

 

[DaveC426913]

What are your thoughts on the matter?

 

[symbolipoint]

Do they perform metabolism, even if using a hosts organisms cells to do so?
Are virii irritable?
Can they reproduce?

If yes to all of those, then virus seems to be life.

 

[DaveC426913]

Are virii irritable?

As a discrete unit, no.

Can they reproduce?

As a discrete unit, no.

Virii corrupt living cells. Arguably, it is the living cells that is doing the irritation and reproduction.

 

[Moridin]

One of the main issues with discussions whether viruses are living or not, is that we are trying to establish a discontinuous, essentialist barrier on what is most probably a continuous transition. None of the proteins, carbohydrates or lipids in your body are alive, however, in certain configurations together with other building blocks, something we call life emerge on a higher level of analysis (but of course completely explicable from these basic building blocks; no particular elan vital or life force).

 

[mgb_phys]

As a discrete unit, no.
Virii corrupt living cells. Arguably, it is the living cells that is doing the irritation and reproduction.

Virii have inheritable traits that they pass on to their offspring so they are alive.
They can't reproduce without a host cell but lots of species can't reproduce without a host body, from tape worms to cuckoos.

 

[DaveC426913]

Virii have inheritable traits that they pass on to their offspring so they are alive.

Logical phallacy: hasty conclusion. That is not the only criteria for life.
[/QUOTE]

 

[granpa]

all living systems depend on some external factors beyond their control for survival. we depend on the sun for energy. are we therefore not really alive?

reproduction and the ability to evolve are the 2 most basic necessities for life. but like all categories, inclusion within the category 'living' is not all or nothing. see the wikipedia article on 'fuzzy logic' for more on that idea.

 

[CRGreathouse]

I'd like to see some examples of creatures that can't reproduce on their own -- I'm sure there are some corner cases. That might be an illuminating comparison.

Grammar nazi alert:
1 virus, 2 viruses; 1 criterion, 2 criteria.

 

[cesiumfrog]

Logical phallacy

Whatever you say, Freud.

 

[Moridin]

all living systems depend on some external factors beyond their control for survival. we depend on the sun for energy. are we therefore not really alive?

reproduction and the ability to evolve are the 2 most basic necessities for life. but like all categories, inclusion within the category 'living' is not all or nothing. see the wikipedia article on 'fuzzy logic' for more on that idea.

Hard to evolve if you cannot reproduce.

 

[DaveC426913]

Whatever you say, Freud.

 

[DaveC426913]

I'd like to see some examples of creatures that can't reproduce on their own -- I'm sure there are some corner cases. That might be an illuminating comparison.

Grammar nazi alert:
1 virus, 2 viruses; 1 criterion, 2 criteria.

Then you don't believe in:
1 forum, 2 fora
1 vox, 2 voxen

 

[Andy Resnick]

1 mongoose, 2 mongooses
1 axis, 2 axes

This is fun!

 

[philnow]

Every living this is dependent on something, as has been said. I don't think that virii require host cellular machinery is sufficient to rule out virii are "alive".

Really, this could all be straightened out if we had a better definition of life.

 

[DaveC426913]

Every living this is dependent on something, as has been said. I don't think that virii require host cellular machinery is sufficient to rule out virii are "alive".

But it's more than merely a dependency. Sorry, I can't back that up with facts...

Really, this could all be straightened out if we had a better definition of life.

(Sorry phil, but I gotta: ) This is kind of stating the exceedingly obvious. No discussion of "is a virus alive" in the history of the universe has gone more than 3 nanoseconds before resulting in the question "what is the definition of life"? And it's never been satisafactorily answered.

 

[granpa]

Hard to evolve if you cannot reproduce.

what is your point exactly?

 

[ViewsofMars]

Are viruses life?

Good question. Thank you. (A nice break from what I had planned to do.) What came to my mind is a quote, "Viruses today spread genes among bacteria and humans and other cells, as they always have... We are our viruses " by Lynn Margulis, 1998, Symbiotic Planet: A New Look at Evolution, Basic Books, 1998. p 64. This link tells you about Lynn Margulis. If you would like more information about her I can provide it.
http://en.wikipedia.org/wiki/Lynn_Margulis

And what a fasinating and awe inspiring world it tiss even when one is flat out tired from a four day wedding event of a good friend.

 

[mgb_phys]

Logical phallacy: hasty conclusion. That is not the only criteria for life.

No - but it's a good one

The question is of course - what is life? I was just putting forward one definition.

 

[philnow]

That's more of a definition of one of the factors in a list of criteria for life. That sole statement has never been a definition of life in itself.

 

[Moridin]

what is your point exactly?

Reproduction is already included in the criteria for evolution, so it is uncalled for to state it a second time.

 

[ViewsofMars]

The question is of course - what is life? I was just putting forward one definition.

Good answer. The question is too. What is life?

Here's an excerpt from NASA-Astrobiology Roadmap, Goal 3: Understand how life emerges from cosmic and planetary precursors, Perform observational, experimental and theoretical investigations to understand the general physical and chemical principles underlying the origins of life:

Origins and evolution of functional biomolecules. Life can be understood as a chemical system that links a common property of organic molecules—the ability to undergo spontaneous chemical transformation—with the uncommon property of synthesizing a copy of that system. This process, unique to life, allows changes in a living molecular system to be copied, thereby permitting Darwinian-like selection and evolution to occur. At the core of the life process are polymers composed of monomeric species such as amino acids, carbohydrates, and nucleotides. The pathways by which monomers were first incorporated into primitive polymers on the early Earth remain unknown, and physical properties of the products are largely unexplored. A primary goal of research on the origin of life must be to understand better the sources and properties of primitive polymers on the early Earth, and the evolutionary pathway by which polymerization reactions of peptides and oligonucleotides became genetically linked.
http://astrobiology.arc.nasa.gov/roadmap/g3.html

Science is my baby! I just love it!

 

[DaveC426913]

Life can be understood as a chemical system that links a common property of organic molecules—the ability to undergo spontaneous chemical transformation—with the uncommon property of synthesizing a copy of that system. This process, unique to life, allows changes in a living molecular system to be copied...

Except that it is a definition of organic life.

 

[mgb_phys]

Origins and evolution of functional biomolecules. Life can be understood as a chemical system that links a common property of organic molecules—the ability to undergo spontaneous chemical transformation—with the uncommon property of synthesizing a copy of that system. This process, unique to life, allows changes in a living molecular system to be copied,

There are self-catalysing chemical reactions for which this is true.
there are even a couple of them that take different pathways depending on external conditions and so can be said to adapt. But they don't pass on the 'chosen' properties so don't have inheritance.

 

[ViewsofMars]

Ahhh, a meeting of the minds! Remember it wasn't me that brought up this sub-topic, What is Life?. I admit it is a worthy pursuit and am grateful for the input and our ability to learn by sharing. By far, that is highly important to me and other interested parties. I'm not in the mode to critique only examine pertinent material while enjoying what I love - Science.

Let’s continue onward and further explore by reading the Nobel Prize Organization’s 'perspectives' of What is Life? Erwin Schrödinger's idea that physics could help solve biological riddles was the spark that led many researchers to try to unlock the secrets behind our book of life, the structure of DNA.
http://nobelprize.org/educational_games/physics/imaginglife/documents/article_med_1962.html

As well as WHAT IS LIFE? , ERWIN Schrödinger, published 1944. What is life? The Physical Aspect of the Living Cell. Based on lectures delivered under the auspices of the Dublin Institute for Advanced Studies at Trinity College, Dublin, in February 1943.
http://whatislife.stanford.edu/Homepage/LoCo_files/What-is-Life.pdf

I discover something new each time I open a new door. I did wholeheartedly agree with what the Nobel Prize Organization noted "Looking at heredity from his perspective, Schrödinger argued that life could be thought of in terms of storing and passing on biological information. Understanding life, which would invariably involve discovering the gene, could possibly go beyond the laws of physics as was known at the time, he stated."

 

[//:phoenix:\\]

One of the main issues with discussions whether viruses are living or not, is that we are trying to establish a discontinuous, essentialist barrier on what is most probably a continuous transition. None of the proteins, carbohydrates or lipids in your body are alive, however, in certain configurations together with other building blocks, something we call life emerge on a higher level of analysis (but of course completely explicable from these basic building blocks; no particular elan vital or life force).

Wouldn't that mean they are just pseudo life, in that they cannot live on their own? I would say viruses weren't living things but rather a type of false life as they can't live without infecting a host organism.

 

[philnow]

Erm, so you're implying that they're "alive" when they infect a host but "false alive" when on their own?

 

[DaveC426913]

Erm, so you're implying that they're "alive" when they infect a host but "false alive" when on their own?

Yes. Without a host, they do not metabolize at all; they are nothing more than fragments of DNA in a shell. (Caveat: My facts may be out-of-date and this may be oversimplifying.)

 

[CRGreathouse]

Wouldn't that mean they are just pseudo life, in that they cannot live on their own? I would say viruses weren't living things but rather a type of false life as they can't live without infecting a host organism.

Wouldn't this mean that no parasites are living?