Development of life on earth question

[John21]

I'm assuming two points to ask a question:
1) That life began on earth, regardless of exactly where, how, or at a particular point in time.
2) Since the emergence of life, the process has not happened again.

So my question is: why hasn't it happened again?
Was it simply that macro environmental changes occurred that prevented the particular circumstances from re-occurring?
Or, did the emerging life produced conditions that would prohibit a future emergent process?
Do we know?

[luckyme]

[ QUOTE ]
So my question is: why hasn't it happened again?

[/ QUOTE ]

And where are the Bison?

Basic resourses are exhausted when all supply is consumed.

luckyme

[peritonlogon]

[ QUOTE ]
I'm assuming two points to ask a question:
1) That life began on earth, regardless of exactly where, how, or at a particular point in time.
2) Since the emergence of life, the process has not happened again.

So my question is: why hasn't it happened again?
Was it simply that macro environmental changes occurred that prevented the particular circumstances from re-occurring?
Or, did the emerging life produced conditions that would prohibit a future emergent process?
Do we know?

[/ QUOTE ]

I think there are biologists who doubt 2).

As for the Neo-Darwinian answer assuming 1) and 2) it would go something like this. The raw materials which would be needed to start life anew is already in heavy demand and existing life forms are already competing hard to aquire them. So, the circumstances of life begining from scratch again don't exist since the materials of life are in use, and if some life form were to miraculously begin to exist, it would probably not last long against organisms that have been here for millions of years.

[madnak]

There are biologists who doubt 1 and 2.

Best responses? Well, for one the environment has changed dramatically. Our current atmosphere is probably not very conducive to the formation of life. Oxygen has a tendency to disrupt things, for example.

Also it took billions of years to happen the first time. Not exactly an everyday thing. Even assuming ideal conditions, we don't know exactly how long it takes to happen "on average." But it's probably in the billions of years.

Finally, the life present here would probably elminate the beginnings of new life even if it were to "beat the odds."

[John21]

So loosely, can I say something to the effect that the energy contained in life on earth forms some sort of closed quantum?

I'm trying to work my mind around the concept that with the aid of the sun's energy, biological evolution (as a whole) is kind of forcing itself uphill against entropy. Or with the above definition: the quantum of life energy on earth is using the sun's energy to counter the 2nd law in a closed system.

I'm not assigning or implying any purpose to the process, just trying to grasp the abstract concept behind it.

[tolbiny]

[ QUOTE ]
the quantum of life energy on earth is using the sun's energy to counter the 2nd law in a closed system.


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Kind of. Its more like the earth isn't a closed system because the sun inputs energy into it.

[madnak]

It's not. Life is physically entropic. "Entropy" in the physical sense isn't quite the same as what many of us would call "chaos." The free energy of the universe is going down. In fact, life forms are stable largely because they're "destruction machines," constantly moving energy into more disorganized forms.

That's, hey, that's what we do. The energy from the sun is just what allows us to keep "destroying" order without ever "running out." Energy from the sun powers endergonic reactions in plants and bacteria through electron transport chains. Then the stored energy from that is stored again as exergonic reactions power new ("weaker") endergonic reactions to create storage compounds (glucose primarily). Those compounds are broken down into new exergonic reactions that power new endergonic reactions when the cell needs energy (ATP), and then those molecules are broken down to power cell machinery or new endergonic reactions. I know it gets way more complicated than that, but the point is that at every "step" energy moves to a less organized state (heat).

There is no closed system at all - every living system must get fuel from outside, because every living system is inherently destructive/entropic. Similarly, populations and ecosystems require inputs of more-organized energy to "destroy," and the biosphere as a whole requires the energy of the sun for that purpose. The second law of thermodynamics isn't violated by living systems.