The Definition of Life

I was reminded of this in the thread 'So . . .'

How can you tell if something is alive? Not necessarily alive or dead, just alive or non-alive.
I believe you can't tell, that 'life' is not a property that something can have.

Does anyone disagree?

your table in front of you would be in a state of non-alive.

Yet you would be in a state of alive.

In other words i disagree

But can you prove that the table is non-alive?
Can you prove I am alive?
How did you know I had a table in front of me?

Why is the table non-alive? How did you decide that? Also, on a molecular basis, where do you end, and the rest of the universe begin? Is the hair on your head (assuming you have some ) alive, or where does it become non-alive?

this depends on your definition of life. I don't do biology but don't you need to consume and expend waste?

And you are on a computer are you not?

for an organism to be classified as living it must:

be able to respire (breathe)
(as Tim09 said) Expell wastes
Consume nutrients (cant think of the term but yeah.. eat stuff)
Be able to reproduce
It must be able to grow

etc.. cant remember the other conditions

Why must it be able to reproduce?

Surely it's just a matter that it must be a sustainable species, so theoretically it could handle that by being one massive plant that never actually breeds or dies (until we chopped it down to make Xavier's desk).

hehe but how did that tree get there in the first place? By reproduction! It would have to have the ability to reproduce.. just nothing to reproduce with.


A species is not sustainable if it doesnt have the ability to reproduce, no matter how long it lives for. Every living organism has the ability to reproduce.. thats what (biologists say) the meaning of all life is.. to reproduce and survive

Not every species last forever - that's what we have 'extinction' for ^_^

Siobhan Griffin wrote:Not every species last forever

Yeah, but they have a good crack at it before they do become extinct...
I dont think thats the argument at hand tho.

tim09 wrote:this depends on your definition of life.

I think that's what we're debating, the definition, not the meaning.

If you are looking for the meaning, go to the thread called "So...".

What I'm asking, slightly off topic I'll admit, is where the living organism ends, and the "rest" begins?

When it stops changing, I guess.

No no, not in time, physically. Where do the tree's molecules end, and the "rest" begin? The bark on some trees is not growing, supplied with nutrients or water. The same with "dead" skin cells. Where does the living organism stop?

When the core of the organism stops changing and all contiguous parts of the organism stop changing, the organism as a whole - which includes the 'dead' parts (bark, hair and whatnot) that are contiguous shifts from the living status it had, to a 'dead' status.

I'm not asking about whether its alive, I'm asking if the bark is alive, and if not, where you draw the line as to whether a "cell" say, is part of the living organism. Assume we are talking about a single point in time, and this "tree" is in the prime of its "life".

Too many inverted commas... I need to explain myself better.

My question: Where in space does the living organism end, and where do the non-living things begin.

Alex Steiner wrote:I'm not asking about whether its alive, I'm asking if the bark is alive, and if not, where you draw the line as to whether a "cell" say, is part of the living organism. Assume we are talking about a single point in time, and this "tree" is in the prime of its "life".

Too many inverted commas... I need to explain myself better.

My question: Where in space does the living organism end, and where do the non-living things begin.

The bark is more like the shell of a turtle, which isn't part of any biological systems (respiratory, cardiac), the bark of a tree can be ripped off with no adverse affect to the health of the tree, just leaving it open to physical damage in the future. It's like a human with a shield, if our shield breaks, we don't die.

Siobhan Griffin wrote:When the core of the organism stops changing and all contiguous parts of the organism stop changing, the organism as a whole - which includes the 'dead' parts (bark, hair and whatnot) that are contiguous shifts from the living status it had, to a 'dead' status.

So as above, a 'living organism' is a contiguous organism that at least one part of is still changing - doesn't matter how much dead material is wrapped around it.

So where does the tree end, and the "shell" begin? And can you give other examples of this? Also, when something "dies", bacteria and chemical processes begin to break the bonds between the different parts. Does this make it alive, because it is changing?

Also, if you go right down, what makes a molecule, say, part of the living organism? For example, the iron in your red meat; when is it part of you, and when is it just "in" you? Assuming you're not a vegan.

I like a good, completely pointless debate.

Alex

The shell is part of the tree, so it doesn't

Sea Urchins, dogs, birds and fish would all be other examples of this.

And yes, yes it does. I could argue soul with you, but that would take this into religious grounds I'd rather not slug it out in ^_^ Physically, yes it does make it alive even as it decomposes - or containing life, which is more to the point.

A molecule is 'part' of a living organism when it moves with it. So your food within you is part of you and is no longer part of you when you excrete it. And a baby is part of you until it is born.

Sorry, debate over

So, the laptop that moves with me as I carry it in a bag is part of me? Or something not quite so extreme, a band-aid over a cut on my arm (example, not actually there).

You're right, I'd rather avoid soul.

Also, what do you say to thing that live in the tree, such as termites? are they temporarily part of this meta-organism? And since the Earth moves, and changes, is it alive. Or the sun?

These points are backwards, so just link them to your points.

And it's not over 'til the fat lady sings.

Spoiler:

You maybe...

Ah finally i get your question!!!

something is part of an organism if its genetic code is EXACTLY THE SAME as the thing its attached to.

For example.. the cells in your arm is Genetically exact to the cells in the rest of your body.. therefore your arm is apart of You (the living organism)

A leech attached to your leg, has a completely different genetic code to your leg so it is not PART of you its merely ATTACHED but it IS alive. The band-aid would not be alive as it has absolutely no characteristics of life and is not part of you at all, merely attached

I hope that answers ur question.. please tell me if it doesnt and ill try explain it another way, or if i read your
question completely wrong


EDITED

Well, it's not really about answering my question, just arguing about it. I was really looking for others' opinions.

I think the thread is for deciding on a universal and generally agreed upon, definition of life; as in, a set of criteria, that if met, define something as "alive".

I think we need that before we can "answer" my question.

Tecchi wrote:for an organism to be classified as living it must:

be able to respire (breathe)
(as Tim09 said) Expell wastes
Consume nutrients (cant think of the term but yeah.. eat stuff)
Be able to reproduce
It must be able to grow

etc.. cant remember the other conditions

I did, got a whole list of em in Biology.. add that to my explanation.


EDIT: I remember 1 more.. a vital 1.. all living things must be made of at least 1 cell...

How do you define cell? Also, reproduce, consume, and respire?

These all link to the point of no life, where the organism ends, and the stuff stuck on it begins. (BTW, dead skin cells have the same genetic code as the rest, but are not "consuming" nutrients)

These points also only cover the organism as a whole, not parts of it.

Dead skin cells are still part of the living organism, so the same genetic code response works.

Tack 'organic material' and 'same genetic code' into my earlier explanation and I'll stand by it

As for your little spoiler... meet me in MSN and we'll see if you're still so cocky