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Thread: When do we consider something "live"? What are the "requirements" of life?

  1. #1 When do we consider something "live"? What are the "requirements" of life? 
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    When can we say that something is alive and therefore can be distinguished from "dead matter"?


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    Quote Originally Posted by N0VUS View Post
    When can we say that something is alive and therefore can be distinguished from "dead matter"?
    Opinions differ. Key features would be self replication and descent with modification. There's no real distinction between living matter and dead matter in itself. The carbon atoms in your DNA are no different to the carbon atoms in a pencil.


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    We tend to make distinctions and comparisons to understand our world. We break things down into individual examples. Maybe life is actually a coordinated effort of the universe, rather than the individual effort of each "living" being. In which case everything is alive. Or maybe we are distinct from viruses or even monkeys. Maybe life is sentience, or perceived sentience (in which case, your computer could be said to be alive). Does life have DNA or RNA? What is it about these chemicals that cause us to define them as life? They may be the blue prints of our beings but at this point, at least in humans, the DNA would not go so far without the help of the being which it expresses (as in the rest of the mind and body). I imagine the best one could do is pick a subject to discuss and agree on the definition ahead of time.
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    This is a perennial topic, discussed over and over by persons interested in biology all round the world. There is no universally agreed answer, though The Biologista's answer is about as sensible and realistic as you are likely to encounter.
    Last edited by skeptic; July 22nd, 2011 at 09:20 PM. Reason: spelling
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    The inadequacies of language come to the fore when you try to define life rigorously in a catchy little sentence that you can easily regurgitate on demand. There is also, I think, a difference between "life" and "alive" to make things a little more muddled. The alternative to a simple definition is to produce a list of criteria that must be met; however, biology is an old hand at throwing up difficult exceptions that ignore one of the requirements.

    The simplest (that is, shortest) and most useful definition is perhaps that proposed by NASA sometime in the 1990's: "a self-sustaining chemical system capable of Darwinian evolution" which is more or less what The Biologista said. As far as I can tell this definition will only breakdown when confronted by non-biological beings from the world of science-fiction.

    Life is a property of living systems and generally only becomes problematic when you go to extremes: are viroids alive? Or ecosystems?
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    Quote Originally Posted by Zwirko View Post
    The simplest (that is, shortest) and most useful definition is perhaps that proposed by NASA sometime in the 1990's: "a self-sustaining chemical system capable of Darwinian evolution" which is more or less what The Biologista said. As far as I can tell this definition will only breakdown when confronted by non-biological beings from the world of science-fiction.
    Nothing is self sustaining unless you include the environment which contains it, and of course the environment which contains that, and so on. If one part of such a system is capable of "Darwinian evolution" that would make the entire system capable since the evolution would not be possible without the assistance of the system. So, it seems to me that, by this definition, the universe is a living thing.
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    Quote Originally Posted by DaBOB View Post
    Nothing is self sustaining unless you include the environment which contains it, and of course the environment which contains that, and so on. If one part of such a system is capable of "Darwinian evolution" that would make the entire system capable since the evolution would not be possible without the assistance of the system. So, it seems to me that, by this definition, the universe is a living thing.
    We already have a word for the universe. We already know that its components are deeply interconnected in various complex ways. We're trying to make a useful demarcation between life and non-life in the same sense as we distinguish between rivers and oceans, mountains and planes. Not because these things are entirely distinct and sharply separated, but because they aren't. You're broadening the meaning of the word 'life' to the point of making it totally useless.
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    Quote Originally Posted by TheBiologista View Post
    Quote Originally Posted by DaBOB View Post
    Nothing is self sustaining unless you include the environment which contains it, and of course the environment which contains that, and so on. If one part of such a system is capable of "Darwinian evolution" that would make the entire system capable since the evolution would not be possible without the assistance of the system. So, it seems to me that, by this definition, the universe is a living thing.
    We already have a word for the universe. We already know that its components are deeply interconnected in various complex ways. We're trying to make a useful demarcation between life and non-life in the same sense as we distinguish between rivers and oceans, mountains and planes. Not because these things are entirely distinct and sharply separated, but because they aren't. You're broadening the meaning of the word 'life' to the point of making it totally useless.
    Yes, I tend to do that with many things. Whereas you answered the question by saying there is no one answer, I answered it by making the one answer useless. However, I actually haven't defined it myself. I instead was only trying to support the current conclusion, as well as agree with Zwirko, about the language issue.

    I think I still stand by my first response, that the definition must be relative to those using it. However, I think that if we tried to find a single absolute definition I would probably argue that the universe itself is alive. The word "universe" does not automatically imply life. For, if it did, we wouldn't be having this discussion. Therefor I see nothing wrong with saying the universe is alive while the word "life" and "universe" remain two distinct things. The word "universe," to me, implies a certain amount of space and everything within it. "Life" implies a certain direction. At the moment I'm not convinced evolution is the appropriate name for that direction, but I think it's a fine example. It's definitely not an easy thing to define. I think most things aren't however. Language is naturally imprecise. I think if it were precise than life would be less involved (hmm... maybe there's another way to define life, simply as relative or imprecise, but then we already have words for that I suppose). At the moment though, I am not trying so much to support my theory of a single, objective definition. It gets a little philosophical, and it's been so long since I've had to support it that I would probably not do so good.
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    Quote Originally Posted by DaBOB View Post

    Nothing is self sustaining unless you include the environment which contains it, and of course the environment which contains that, and so on. If one part of such a system is capable of "Darwinian evolution" that would make the entire system capable since the evolution would not be possible without the assistance of the system. So, it seems to me that, by this definition, the universe is a living thing.
    This is unhelpful thinking. The phrase "self-sustaining" does not mean that the system is found in complete isolation unconnected to and unreliant upon any other component of the universe.


    I could envisage having a mix of catalytic self-replicating RNAs in the lab. I could control their environment, monitor, maintain and adjust their reaction conditions as I saw fit. This is not self-sustaining because it requires my direct interference - intervention by a higher power, as it were. The RNAs are a chemical system and are also capable of Darwinian evolution; they don't however form a self-sustaining system and thus are not life according to that particular definition. Humans fit the definition because there is no one around to pull the plug on the reaction vessel - we are not artificial, we continue to propagate naturally in a self-sustaining manner. I think your over-stretching the meanings of the terms used in the definition I offered. "Self-sustaining" can have several meanings depending on how you use or define it.
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    Quote Originally Posted by Zwirko View Post
    The phrase "self-sustaining" does not mean...
    Again we run into the constraints and impreciseness of language. I feel there must be a better word than impreciseness. Maybe unpreciseness, but alas, spell check believes that is not a word. How about inaccuracy. The inaccuracy of language. No, I think I need a completely different word. Ah yes, a good sciency word: the relativity of language. I think that is more precise.

    Quote Originally Posted by Zwirko
    there is no one around to pull the plug on the reaction vessel
    I disagree, however I believe that the entity (shall we call it life) that has the capability of pulling the plug is the same entity that is so intent on not pulling the plug. I am being forced into defending myself. I will try to remain as ambiguous as I can.
    Last edited by DaBOB; July 23rd, 2011 at 12:15 PM.
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    Best not to be too ambiguous though. Although language can be imprecise at times, the terms used in a definition may themselves be precisely defined elsewhere (as part of the larger body of work that produced the definition). Each component of a carefully worded definition such as this more than likely has a great deal of argument behind it. It may be better to write the definition as: "a self-sustaining* chemical* system* capable of Darwinian* evolution*" where each asterisk refers one to an extensive discussion of the meaning of these terms, detailing precisely how they are being used in this particular context. Then again., maybe it was just thrown together with little though behind it - I don't know the background of this definition.

    A better test of the NASA definition would be to think of situations where it does not apply. I can think of several.
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    Quote Originally Posted by Zwirko View Post
    A better test of the NASA definition would be to think of situations where it does not apply. I can think of several.
    I see what you mean. I, however, am still unsatisfied by the definition. I'll refrain from sophistry though. I think we understand each other. I think the most important thing, for us anyhow, is that it's a good exercise. Food for thought, as they say.

    Novus, have you any thoughts?
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    The Biologista's two criteria are still the best. Reproduction and evolution.

    The reproduction part excludes mountains, rivers and the universe. The evolution part excludes certain runaway chemical reactions like a forest fire.

    "Self sustaining" is not a criterion. There are simple bacteria that are parasitic and totally dependent on their hosts for large parts of their life sustaining processes. Those bacteria are not self sustaining, yet they are alive.
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    Quote Originally Posted by skeptic View Post
    The Biologista's two criteria are still the best. Reproduction and evolution.

    The reproduction part excludes mountains, rivers and the universe. The evolution part excludes certain runaway chemical reactions like a forest fire.

    "Self sustaining" is not a criterion. There are simple bacteria that are parasitic and totally dependent on their hosts for large parts of their life sustaining processes. Those bacteria are not self sustaining, yet they are alive.




    As I mentioned earlier "self-sustaining" in this context doesn't mean that an organism is dependent upon another for its survival. Wolbachia is a perfectly self-sustaining organism, even though it is an obligate endosymbiont. The term can be loosely translated to mean "reproduction"; I think the term is designed to exclude artificial systems that exhibit both reproduction and evolution (see my catalytic, self-replicating RNA example above). The NASA definition is thus the same as that offered by TheBiologista, except that the term "reproduction" has a caveat attached that necessitates a rewording.

    Imagine if I took my replicating and evolving mix of RNAs from my microfluidics device and chucked them in the nearest farmers field. The reaction mix would rapidly cease to replicate and evolve or, for that matter, be a chemical system. So while in the lab under strictly controlled unnatural conditions they exhibit reproduction and evolution they are not self-sustaining.


    self-sustaining = reproduction; persistence in the natural world; not a lab-bound phenomenon etc.
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    Apologies, first sentence should read:"'self-sustaining" in this context doesn't mean that an organism is not dependent upon another for its survival'".

    Rather drastic difference in meaning with "not" added.
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    Zwirko

    The term 'self sustaining' does not exclude some of those artifical systems you refer to. For example ; there are now many computer programs that simulate life, and the software permits changes caused by both reproduction of the simulated organism, and its evolution. Inside the computer, those simulations are indeed self sustaining. Life on Earth is self sustaining, but depends on the terrestrial environment, as those simulations depend on the computer generated environment.

    I have seen one definition, which used the phrase 'complex system of organic molecules' to exclude such simulations. I do not think the word 'complex' is needed, though. In fact, I suspect it was added purely to exclude viruses. The first life on Earth was, no doubt, a simple system of self reproducing nucleic acids, with other molecules to support that. eg. fatty acids forming a protective vesicle. This simple life slowly evolved into more complex life, and there would have been no point at which you could clearly delineate 'life' after that point, and 'non-life' before.
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    Quote Originally Posted by skeptic View Post
    I have seen one definition, which used the phrase 'complex system of organic molecules' to exclude such simulations. I do not think the word 'complex' is needed, though. In fact, I suspect it was added purely to exclude viruses.
    Are viruses alive? I believe they fit any definition given thus far when in their intracellular phase. Are they dead when they're outside a host cell? Personally, I'd consider them alive but 'inert', the same as fungal spores or plant seeds that are still viable, but haven't germinated. Then, wouldn't the potential to at one point become a self-sustaining, replicating entity possibly be classified as a lifeform?
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    I don't mean to be rude Skeptic, but I don't understand why everyone who has responded to my comments has failed to grasp the meaning of self-sustaining as it is being used in the context of this definition. From this discussion I think I've maybe been convinced that "self-sustaining" is a somewhat problematical wording and could perhaps be re-worded. I wouls still maintain that the term adequately deals with computer programs and chemicals in a test-tube. I'm getting a little frustrated that my lack of literary skills prevent me from finding a better way of capturing this property of life that distinguishes it from something like a batch of replicating and evolving chemicals. In fact, I now have a thumping headache so I'm gonna quit on this issue before I suffer a stroke.


    My original intention was to merely throw this defintion out in to the discussion as being one of the more robust definitions we have. Since I now find it quite a good one and note that the definition itself has not been seriously challenged with a possible exception, I will defend it some. For example, a computer program that simulates life fails because it is not *ahem* self-sustaining, nor a chemical system (it's electrical charge stored on a chip). I'd also argue that it doesn't evolve, but merely simulates evolution (I understand and accept that others would see that differently though). We also should note that the definition "reproduction + evolution" fails to exclude a life-simulating program. By adding "self-sustaining" and "chemical system" we can exclude such a program. As you say, "a complex system of organic molecules" also gets around the problems these programs can present to many definitions of life. Likewise, a microfluidics chip with a population of rapidly replicating and evolving RNAs would also be classed as life if we used the two criteria of reproduction and evolution or if we used "a complex system of organic molecules". It fails to be classed as life under the definition I presented - if we can get to grips with the contentious term mentioned at the top of this post, or find a new way of expressing this property.

    I know there are more definitions of life than we can shake a stick at, many of which have minor niggles or can't deal with everything we throw at them - that's what happens when you try to define the most complex thing in the universe in a funky little one-liner. Other than the quaint, and not terribly useful, "life is a property of living systems" I'm coming round to the opinion that the definition I presented is the strongest that I've seen. Ignoring some hypothetical scenarios one could dream up from the realms of science-fiction I can't think of a situation where the definition has a major problem. I'd be interested in learning about any examples that escape this definition. The best I could come up with on short notice was prions: chemical system; self-sustaining; capable of evolving (sort of). I'd be very reluctant to describe prions a life however.




    Spoonman, it's fashionable these days to view viruses as life (although many would still refuse to accept them and could maybe build a strong case in support of their opinion). Can we have non-living life? As you point out, the virion (virus particle) would be better described as being inert, rather than dead. Their complex life cycles and intracellular phase makes a strong case for them being life. A few virologists have suggested that the infected cell is actually the virus, the particle just being equivalent to a spore. In such a hypothesis we are asked to think of a virus as being like an organism that is too lazy to have its own cell. The idea has some merit and is fun to think about rather than being one that is taken seriously.
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    Quote Originally Posted by Zwirko View Post
    A few virologists have suggested that the infected cell is actually the virus, the particle just being equivalent to a spore. In such a hypothesis we are asked to think of a virus as being like an organism that is too lazy to have its own cell. The idea has some merit and is fun to think about rather than being one that is taken seriously.
    I've never heard this before, it's quite an abstract and interesting way to view the 'life'-cycle of a virus but I imagine it has little scientific usefullness when studying the molecular biology and pathology of viruses, it would be difficult to include the innate cellular-response to the infection into this definition. Nevertheless, as you said, it's fun to think about.

    What this discussion has made me realise is that, in order to accept a working definition of life, you may have to accept some short-comings and exceptions, and the best/strongest definition is the one that has the least exceptions. Bare in mind that such exceptions that have been raised in the discussion include computer simulations that have only relatively recently been produced. Before these, definitions that have been stated would have had almost no exceptions (at least none that I can think of). Maybe in the near future, novel scientific terminology will be able to produce a working definition with no exceptions. But for now, the option seems to be, either accept some short-comings or ignorantly conclude that everything is alive or everything is dead.
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    Quote Originally Posted by spoonman
    What this discussion has made me realise is that, in order to accept a working definition of life, you may have to accept some short-comings and exceptions, and the best/strongest definition is the one that has the least exceptions. Bare in mind that such exceptions that have been raised in the discussion include computer simulations that have only relatively recently been produced. Before these, definitions that have been stated would have had almost no exceptions (at least none that I can think of). Maybe in the near future, novel scientific terminology will be able to produce a working definition with no exceptions. But for now, the option seems to be, either accept some short-comings or ignorantly conclude that everything is alive or everything is dead.
    The issue here is language. For example, I may use words like velocity, force, and power all the time. These words have meaning but I'm probably not giving them the same meaning as a physicist would. The word life is especially difficult. There are many fields of study which use the term. Physics, biology, medicine, philosophy, etc. To some it's more important to define and in some fields the definition may change among users. The way different people define it can have enormous significance. In the field of medicine for example, a person's understanding or definition of the word may effect the way they work. Or someone who is dying may be treated differently. Language is imprecise. The thing to remember is that language is a human construct, and it is something we share. Even if all of the worlds biologists decided on a single definition someone would be unaware of flat out disagree. Rather, we need to develop situation specific definitions where they are needed and leave the rest to philosophers.

    I often think of machines as alive. It may seem as though I'm just trying to think of way off topic things for the sake of argument but it's not so. Machines, over time, develop a certain personality because of how they are used and how they wear. They appear alive and in treating them as a living thing they function better than if treated as a lifeless thing. You could say rather than having their own life they are an extension of our life. What's really cool about this is that a number of minds probably went into making it and then any number of minds also go into using it. So this extension to our life is made up of many lives rather than just our own.

    I'm not sure how many people here are familiar with the anime Ghost in the Shell. One of the main themes is this very question. If you have a human with a fully prosthetic body, and the only thing still from the original human is the brain and spinal cord, which are also both augmented are these people still living beings? The "ghost" is often what the characters refer to as something that reminds them they are alive. They get "ghost whispers" or feelings. At what point do we have so many prosthetics that we are no longer considered alive? The character's augmented brains are called cyber brains and they can transfer their ghost from one to another. The main character had an AI merge with her (classic scifi). Can an AI be alive? If it is able to sustain it's life and evolve, as our popular definition says? How is evolution measured? Is evolution progress, or just evolution? When it gets down to it evolution is just survival, isn't it? Then, we could say life is anything which can take part in it's own survival.
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    Quote Originally Posted by DaBOB View Post
    The issue here is language.
    Agreed, but what I said is entirely relevant to creating a working definition... expect and accept short-comings and exceptions.

    Quote Originally Posted by DaBOB View Post
    I often think of machines as alive. It may seem as though I'm just trying to think of way off topic things for the sake of argument but it's not so. Machines, over time, develop a certain personality because of how they are used and how they wear. They appear alive and in treating them as a living thing they function better than if treated as a lifeless thing. You could say rather than having their own life they are an extension of our life. What's really cool about this is that a number of minds probably went into making it and then any number of minds also go into using it. So this extension to our life is made up of many lives rather than just our own.
    Yes, we frequently personify or anthropomorphise objects that appear to do things unexpectedly. Which is why when your computer flashes up an "error" message and it simultaneously closes Word document you were working on, you shout at it as though it were a person. The machine doesn't develop a personality, rather, you develop one for it in your mind. We always personify objects: cars and boats are often referred to as 'she' by people where I'm from (not sure if it's a global thing).

    Here's an interesting article I read last night about creating self-replicating RNA in the lab, eliminating the need of any protein or membranes. They were able to create different 'species' and mix them together, there was some recombination and a new 'species' evolved that was able to reproduce faster than the others. The resulting population had very little of the beginning species, and one dominant species reproducing exponentially: Health | Alien life-forms may be nearer than you think | Seattle Times Newspaper
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    Quote Originally Posted by spoonman View Post
    The machine doesn't develop a personality, rather, you develop one for it in your mind.
    Yes, it's the same way we communicate with other people too. Ever caught yourself being romantic, talking, or arguing with someone in your head. Ask yourself who you are communicating with. Then, when the person is actually around are you still communicating with the fantasy person or the real one? Personality to me seems more a creation of the observers than the observed. Do you ever notice many people say you are a certain way, and find yourself disagreeing? Your car is probably wondering why you always refer to him as a her.

    This is an entirely different topic though. Yet, I still think it is tangentially related (are those two sentences contradictory?). Life is a construct of our minds. Are things not life simply because we know they are man made? Who's to say we aren't just machines made by someone else and our function is simply to imitate life? Or to define ourselves as such? In that case it might not even be a problem of language because we would be adopting someone else's language which may or may not be more precise. I feel I have left the realm of biology, and maybe the realm of reason.
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    Quote Originally Posted by DaBOB View Post
    Your car is probably wondering why you always refer to him as a her.
    Lol.

    Quote Originally Posted by DaBOB View Post
    Life is a construct of our minds.
    I think this is entirely relevant and also true. Perhaps this thread would have been more suited to the philosophy forum. We're trying to define life as a set of biological and chemical parameters when the idea of something being alive is a formulation of our intelligent minds. Although, in biology, a working definition is often useful.
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    Novus, have you any thoughts?
    Sorry, I haven't been near to computer for a while (I was in Egypt).

    My thoughts?

    I don't know (most likely I will never really know).

    The reproduction part excludes mountains, rivers and the universe. The evolution part excludes certain runaway chemical reactions like a forest fire.
    The reproduction part also excludes eunuchs, catholic priests, homosexual, and any asexual or sexually impaired organisms, while it would contain many computer programmes (almost anything which is programmed to, for instance, stupid spawning NPCs)

    The evolution part is just too broad I think. Everything evolves, the universe, the forum, ideologies, cities, technology, philosophy, even forest fires.

    So, I guess that's not 100% right.
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    Quote Originally Posted by N0VUS View Post
    The reproduction part also excludes eunuchs, catholic priests, homosexual, and any asexual or sexually impaired organisms, while it would contain many computer programmes (almost anything which is programmed to, for instance, stupid spawning NPCs)

    The evolution part is just too broad I think. Everything evolves, the universe, the forum, ideologies, cities, technology, philosophy, even forest fires.

    So, I guess that's not 100% right.
    Novus

    These discussions refer to species, not individuals. It does not matter that a eunuch cannot reproduce, because his species can.

    And no. Not everything evolves. True evolution is restricted to life and simulated life. Not even ideas, which change by a different process.

    The definition of life I offered before seems to cover all that.

    "Life is a system of complex organic chemistry which is able to reproduce and undergoes evolution."

    It is possible we may discover something in the future that is living but does not fit this definition. But for now, the above definition seems adequate.
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  27. #26  
    Forum Professor Zwirko's Avatar
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    Quote Originally Posted by skeptic View Post

    "Life is a system of complex organic chemistry which is able to reproduce and undergoes evolution."

    It is possible we may discover something in the future that is living but does not fit this definition. But for now, the above definition seems adequate.
    Conversely (just to be a pest), we may observe things today that fit this definition but are not living.
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    Quote Originally Posted by Zwirko View Post
    Quote Originally Posted by skeptic View Post

    "Life is a system of complex organic chemistry which is able to reproduce and undergoes evolution."

    It is possible we may discover something in the future that is living but does not fit this definition. But for now, the above definition seems adequate.
    Conversely (just to be a pest), we may observe things today that fit this definition but are not living.
    Well, actually, if they fit the definition, and it was the definition we agreed on than they would be living.
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    Quote Originally Posted by DaBOB View Post

    Well, actually, if they fit the definition, and it was the definition we agreed on than they would be living.
    Viruses are capable of complex chemistry and they can evolve, yet there is debate on whether they can actually be classed as being "Alive". The term can be used very adaptably which leads to a lot of confusion, there is no one set definition for the word and this means there are many different answers for the original question...
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    Thought for the day: is the polymerase chain reaction a living system? If not, why not?

    > (Non-living in my book).
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    Life, is like a box of chocolates.
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  32. #31  
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    Quote Originally Posted by Zwirko View Post
    Thought for the day: is the polymerase chain reaction a living system? If not, why not?

    > (Non-living in my book).
    Strictly speaking, no. I am quibbling on definitions, mind you. The chain reaction is a process, not a system.

    You could reword it in a more difficult form if you wanted.

    There will always be a stage in this definition where it is necessary to draw arbitrary borders, between what is living and what is non living. A virus is one example. Is it alive or not? The other example which comes to my mind is in the early development of life on Earth. At which point in the development of organic and replicating molecules do you stop calling it chemistry, and call it life?
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    墨子 DaBOB's Avatar
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    Quote Originally Posted by skeptic View Post
    Quote Originally Posted by Zwirko View Post
    Thought for the day: is the polymerase chain reaction a living system? If not, why not?

    > (Non-living in my book).
    Strictly speaking, no. I am quibbling on definitions, mind you. The chain reaction is a process, not a system.

    You could reword it in a more difficult form if you wanted.

    There will always be a stage in this definition where it is necessary to draw arbitrary borders, between what is living and what is non living. A virus is one example. Is it alive or not? The other example which comes to my mind is in the early development of life on Earth. At which point in the development of organic and replicating molecules do you stop calling it chemistry, and call it life?
    Skeptic. At what point is something not a chain reaction? Actually, "chain reaction" is a great way to explain the Dao. Life is essentially a chain reaction, except that it seems we have the ability to alter that reaction to some degree in a particular direction. Then again, our tinkerings and consciousness may simply be a link in this chain reaction. This still does not help us to decide whether a chain reaction is life. isn't a system a system of chain reactions, just as a chain reaction is a chain of reactions.

    Something I am curious about is how do we distinguish the changes of the universe and the changes of a chemical organism. We say that living things evolve. Ok, but what are they evolving to? Evolution may just be a joke. Maybe a more precise term should be devolution. Evolution is essentially the meaning of change but with a direction do to certain influences (chain reactions?). What defines the direction? What makes the direction of the evolution of chemical systems different from non-chemical systems? If life came from accidental happenings of the universe than the universe must somehow be taking part in this evolution. Non-chemical systems do replicate but not in such an observable way. Rocks wear but other rocks are formed. Water is consumed and later secreted. The human body is not replicated any more so than these systems. Rather, the DNA is replicated. So does that make the organism non-living but the DNA living? Or does it count as the whole organism just because that organism contains DNA? The universe contains DNA.

    I think my sole purpose in life (or inanimateness) is to make all questions inconclusive.

    As a side note, what is the antonym for "life?" For example, if we were to decide that organisms aren't actually alive what would we call it. If I were having a conversation with someone would I say "oh yes, I've been studying that all my death, and plan to study it until the day I live." I kind of like that actually.
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    To DaBob

    Reproduction is not simply the creation of another similar material. A rock being worn down and another rock forming is not reproduction. We might as well say that tables reproduce because a furniture factory churns them out.

    Reproduction is the copying of information in a complex structure and using that information to make another version. Life carries information in the form of genes, and those genes are copied and carried with the new organism. Without information, there is not reproduction. A rock or a table does not carry the information for its own creation within.

    Similarly, evolution is not just change. Evolution requires natural selection, which means that many if not most changes are eliminated. Only the changes that lead to the new organism being adapted well to its environment will, in the long run, survive. The universe changes, but there is no selection of which changes survive.

    Your comments on DNA skim over the truth. Life is basically information, in the form of nucleic acids. This information is copied as it is passed down the generations, and some of the 'errors' in the copying process are retained long term, while others are eliminated - all by the process of natural selection.
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