Joined: Mar. 2006
I hope you'll pardon a reply and stupid questions from a definite non-scientist, but:
|1) A self replicating molecule or self replicating series of molecules or a series of interacting molecules that template the synthesis of other molecules.|
It seems to me that this is a basic requirement for us to term anything as "bio" (living or life-like) at all...is that right?
In that case, I would venture to guess that this would have to occur first, *except* that:
3) A series of effector molecules/physical scaffolding/chemoselective processes which allow for a relatively high level of "copying fidelity".
I don't quite understand this requirement. If there is zero "copying fidelity," how can we understand a set of molecules to be "self-replicating" in the first place? By identifying this as a requirement, doesn't it logically follow that 1) cannot occur without this?
I feel like I'm missing some important subtlety or detail here...wonder if you can help me out.
2) Some form of cellular encapsulation, which at least must incoporate a semi permeable membrane or barrier.
Daniel Dennett (not a scientist, I know, but certainly more well-read than I am) takes an interesting perspective on one aspect of life: the separation, or "dividing line" between the organism and its environment.
One property of living organisms seems to be that they expend energy to keep everything "inside" them ordered, essentially fighting against the increasing entropy of its environment and the universe at large.
For us, I guess the "line" would be our skin, or our epithelial layer, which (as I understand it) covers every part of our body that is exposed to the environment and literally acts as a wall, allowing us to expunge "disorder" (waste) while keeping out disorderly material from our environment.
But it seems like the line isn't quite as clear for some organisms; I think ants are an interesting example. If one of the requirements for calling something "living" is the ability to replicate on its own, then a single worker ant isn't technically "alive," is it? I.e., only one member of the colony, the queen, is actually capable of producing offspring.
If we look at the colony at large, though, it's the colony that replicates, right? If the queen dies, another ant becomes the queen so that the colony can continue to replenish itself. Therefore, it seems to me that the ant *colony* is in fact the "living" entity, while individual ants are "parts" necessary to make it work.
If that's true, then the "dividing line" isn't quite so clear anymore...the organism doesn't "end" at the exoskeleton of each individual ant, but includes a good portion of the environment, as well - e.g., the chemical trails that direct each ant to its task.
All of this is a long-winded way of saying that, if a similar situation can apply at a molecular level (not sure if it can), then 2) may well have developed after 1) and 3). Again, not being a biologist or chemist, I have no idea if this is actually possible, but at least conceptually, I can imagine it.