Spark versus murk.

[Learjeff]

@Stranger_On_A_Train

Viruses are not ‘alive’ by and functional definition of life. That they interact with other proteins and can alter the functioning of cells is not in question, but the inability to self-replicate and self-repair (due to the lack of any kind of functioning metabolism or energy storage mechanism) makes them fundamentally non-living. They are best viewed functionally as a really complex, multifunctional enzyme.

And yet they proliferate and evolve. See? They’re not “red herrings” but borderline cases that help us hone in on what we mean by “life”. I say “borderline” but I do not say that viruses are organisms. But are they life-forms of some sort? I say yes, but that’s a purely semantic statement.

Every single organism–that is, everything that has an intrinsic ability to regulate energy usage and storage via internal mechanisms, and use that energy to maintain and reproduce itself, is cellular in nature. And while we only have data from our single terrestrial cohort, there are some pretty good arguments for why any form of life, regardless of the substrate or information coding mechanism, is almost certain to be cellular in nature. The complex systems which form life are built from very similar, limited individual functions, which themselves arise from a handful of simple amino acids and a long chain information-storing molecule, which are all produced from a few relatively abundant family of atoms. In order to give rise to a functional complex system with sufficient flexibility to evolve in arbitrary fashion, a cellular organization is almost certainly necessary.

I agree, especially the “almost certainly” part. The “almost” part is due to the possibility of life forms that are totally alien to us, and might use some other organizing principle (i.e., as connected together rather than as contained together).

I admit I can only vaguely conceptualize a counterexample. “Almost certainly” is apt. Until we have a good data point to convince us otherwise, it’s a good principle.

[Becky2844]

naita thank you! I’ve been trying to find it.

Day-um, this is interesting.

Yes, “zapping the soup” was basically what I was wondering about when I first posed the questions. From reading these posts and links I’m getting a better grasp of the interactions needed for life. Reproduction seems to be the recurring key though. Am I wrong to wonder if the evolution of the building blocks is a kind of reproduction in itself, because it’s persistent and progressive? And if that’s true, doesn’t have to be confined within a cell?

[Chronos]

It’s a real stretch to call the emergence of the building blocks “reproduction”, because the production of new building blocks didn’t depend on the existing building blocks. It’s like a factory that churns out cars: The factory works the same way if there are finished cars sitting at the end of the line or not. It might even be slowed down by having too many cars at the end of the line, since then there isn’t enough room for new ones. With true reproduction, though, the production of new organisms depends on the old organisms.