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.