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The definition of life

Posted by: SuperShuki - Fri Oct 09, 2009 11:03 am
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The definition of life 
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Post The definition of life   Posted on: Fri Oct 09, 2009 11:03 am
How do you define life? What characteristics would an extraterrestrial entity need to be defined as living?

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Post Re: The definition of life   Posted on: Fri Oct 09, 2009 3:54 pm
DNA?

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Post Re: The definition of life   Posted on: Fri Oct 09, 2009 9:02 pm
traditional definitions of life involve self-replication and reaction to stimuli. i think DNA is NOT a necessary condition for life as it is theoretically possible an alternate chemistry could perform the encoding function differently.

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Post Re: The definition of life   Posted on: Fri Oct 09, 2009 11:43 pm
Selfreplication
Adaptation to medium / hability to adapt the medium to itself
Evolution to progress in getting better on previous points.


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Post Re: The definition of life   Posted on: Sat Oct 10, 2009 8:43 am
Reproduction, Respiration.

Easy, innit. :mrgreen:


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Post Re: The definition of life   Posted on: Sat Oct 10, 2009 6:26 pm
Monkey Liar wrote:
Reproduction, Respiration.

Easy, innit. :mrgreen:

Why respiration? How do you define respiration? Does a bacteria respirate?

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Post Re: The definition of life   Posted on: Sat Oct 10, 2009 6:39 pm
yes they do. respiration is the process of converting sugars into ATP/whatever else energy source. so even plants respirate, after they photosynthesize.

EDIT: as defined, there are probably other chemical energy sources that would not count as respiration so i say that's not a good requirement.

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Post Re: The definition of life   Posted on: Sat Oct 10, 2009 9:57 pm
Why does the process have to be chemical? Isn't it possible for an organism (theoretically, at least) to get energy from, say, atomic nuclear reactions?

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Post Re: The definition of life   Posted on: Sun Oct 11, 2009 4:44 am
Is a virus alive? A Prion?

Ideas replicate, are they alive?

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Post Re: The definition of life   Posted on: Sun Oct 11, 2009 10:04 am
A virus cannot replicate without a host. Of course, many organisms are dependant on other organisms to survive. I think that it would be good to try to pin down exactly what we mean by replication and respiration - or any other definitions of life. Being specific helps.

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Post Re: The definition of life   Posted on: Sun Oct 11, 2009 3:43 pm
idiom wrote:
Is a virus alive? A Prion?

Is it is considerated aislated, no because they couln't selfreplicate itself, but if you define the enviroment of virus as a life cell, then yes, because virus can selfreplicate on a cell. So virus are life inside life. Remove the host and you kill the virus.

idiom wrote:
Ideas replicate, are they alive?

Using the same argument, no outside of human, but yes if you restrict ideas to that enviroment then yes.

OF course, a lot of people restrict the meaning of life only to selfcontained matter with this properties and anothers like methabolism, so the only life we know is carbon life on Earth.
But another people extend that and they don't have problems naming ideas "life" in this sense.


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Post Re: The definition of life   Posted on: Sun Oct 11, 2009 4:12 pm
I think that life can only be defined relative to the life we know. The only way you can define anything is according to what you know. So, be the definition general or specific, it has to be an extension of the life we know of. Otherwise, the definition doesn't have any meaning. Or rather, it has a made-up meaning.

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Post Re: The definition of life   Posted on: Sun Oct 11, 2009 11:00 pm
Better hope it has DNA I'll probably shoot it if it dosen't ! :)

Monroe

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Post Re: The definition of life   Posted on: Wed Oct 14, 2009 7:16 am
Monroe wrote:
Better hope it has DNA I'll probably shoot it if it dosen't ! :)

Monroe

Sorry bout that little buggy :)
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Hey, don't shoot the mRNA.


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Post Re: The definition of life   Posted on: Wed Oct 14, 2009 7:38 pm
I'd like to think of life as an opposing force to decay. Non-living things just are, and wither away over time. Living things keep repairing and recreating themselves. In more physical terms, perhaps we could say that something is alive if it comprises one or more processes that locally decrease entropy?

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