definition of life ?

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sorry if that has been posted before, or if its such an easy question that i shouldnt even be asking it

but i wonder whats the scientific definition of life ?

ultimately, what distinguishes an animal from a plant ? from a rock ?

is there common ground between a rock and an animal ? bewteen a dead body and a living one ?

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We have done this before in other threads, but it is an interesting debatable question.

Without looking up a "classic" definition, I think I would define it something like this:

* Must be able to replicate itself
* Must consume and excrete (this removes viruses from "life" and is probably debatable on that merit, however, it fits my definition).

Replicative molecules are, in my mind, a chemical process. And viruses are parasitic, and can really only exist if there is other "life" around to parisitize. So I tend to rule out these things as being "alive".

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thanks.

i couldnt find the threads talking about it. could link me please ?

Must be able to replicate itself

replicate ? really Confused

i didnt really know the word and thats the definition i found : produce a replica of itself

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miguelito21 wrote:

thanks.

i couldnt find the threads talking about it. could link me please ?

Try this one.

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The famous problem with most definitions of life is that they include "fire".

Fire does everything that living organisms do, It consumes food, excrete waste, breathes air, and replicates itself-- yet no one ever says fire is alive.

My son just came back with his definition of "life" which included all of the normal criteria with one addition... it says to be alive you must be made of cells.

I don't find this very compelling... it will be interesting to see how this classification changes as we learn more about life in the Universe.

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ebrown_p wrote:

The famous problem with most definitions of life is that they include "fire".

Fire does everything that living organisms do, It consumes food, excrete waste, breathes air, and replicates itself-- yet no one ever says fire is alive.

Fire doesn't replicate itself (as in reproduction). It spreads (a purely chemical process). To me that's different.

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'Life' is a difficult definition, one that requires several other aspects--i.e. terrestrial life is carbocentric (theoretically there are other possibilities).

Wikipedia ptovides a short discussion if the definition of Life that includes some proposed definition and discusses insufficiencies.

Interestingly one definition includes 'cell(s)' and consequently define virus as non-life.

Rap

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rosborne979 wrote:

ebrown_p wrote:
The famous problem with most definitions of life is that they include "fire".

Fire does everything that living organisms do, It consumes food, excrete waste, breathes air, and replicates itself-- yet no one ever says fire is alive.

Fire doesn't replicate itself (as in reproduction). It spreads (a purely chemical process). To me that's different.

At the core of our reproduction is the process of "cell mitosis" which is a purely chemical process. In fact, after the act takes place (which isn't even necessary for many types of life), everything is a purely chemical process.

Of course to you that's different than fire... I am just making the point that describing this difference in any meaningfulway is difficult.

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ebrown_p wrote:

rosborne979 wrote:
ebrown_p wrote:
The famous problem with most definitions of life is that they include "fire".

Fire does everything that living organisms do, It consumes food, excrete waste, breathes air, and replicates itself-- yet no one ever says fire is alive.

Fire doesn't replicate itself (as in reproduction). It spreads (a purely chemical process). To me that's different.

At the core of our reproduction is the process of "cell mitosis" which is a purely chemical process. In fact, after the act takes place (which isn't even necessary for many types of life), everything is a purely chemical process.

Of course to you that's different than fire... I am just making the point that describing this difference in any meaningfulway is difficult.

Maybe we should change replication to "replication of information".

Structural information is contained in DNA. Maybe information itself needs to be included in the definition of life.

We need something to differentiate simple chemical processes from "living" chemical processes. As you say, everything is a chemical process at some level, but we still perceive some things to be "alive" and others not, so where is the line drawn.

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DNA is carbonist bigotry.

In the proper environs other elements could prevail over carbon as the basic element of life---

'The ammonia breathing liberation front'
Rap

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raprap wrote:

DNA is carbonist bigotry.

In the proper environs other elements could prevail over carbon as the basic element of life---

Possibly. But if they replicated by splitting and passing information, then the information content would be the process.

definition of life ?

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