Definition of Life

Message 16 of 77 (334207) 07-22-2006 6:48 AM

Reply to: Message 15 by nwr 07-22-2006 12:52 AM

Is a fire alive?

Jon

Message 17 of 77 (334211) 07-22-2006 7:31 AM

Reply to: Message 9 by RAZD 07-21-2006 7:41 PM

Totally agree. After all, stellar evolution plays an essential role in abiogenesis. Even though they're only 2-3 generations old, I have always felt that stars have to be included someway along the non-life--->life spectrum.

Ok, let's start :)

Message 18 of 77 (334222) 07-22-2006 8:19 AM

Reply to: Message 14 by Jon 07-22-2006 12:43 AM

Glad you read it - fascinating eh? You get the feeling that no definition will ever suffice. It certainly seems to cover all the problems.

Maybe what is needed is a definition where you need to have 7 or 8 out of a possible 10 characteristics? A life {pass\fail} score?

I was considering what needed to occur to take the first steps from chemical to life, and had not included {reproduction of the whole} yet in my package for {proto-"ur"-life}, not necessarily going "all the way" at this time.

Technically the mule can still 'evolve' (it can mutate, make copy errors during cell replacement, it can react to the environment to live or die, etc), what they lack is the ready ability to pass on their {changes\adaptations\selection fitness} to another generation.

And any other individual organisms that are sterile, like Lance Armstrong, all females in all species beyond menopause, worker bees, etc. etc. (some mules can reproduce btw, females more than males, just not very common).

Now modern medical science can get around some of these "little problems" - Lance has kids because they froze sperm before the radiation treatments made him sterile, and we also have the grandmother that just gave birth, so it is conceivable () that mules could be reproduced artificially. It is also possible that given enough {testing} that the number of mules that could reproduce would increase (would they become a new species? I think so), but that doesn't answer the question.

One could argue that these organisms are in the process of de-selection ...

The problem is that we are {conflating\equating} the definition of {life in general}, {life for organisms in a group} and {life for an individual} -- as pointed out in the article one (sexual species) individual cannot reproduce without a sexual partner. This kind of requires a definition that is {group} based rather than {individual} based for "advanced" life ... perhaps a distinction between what is {living} and what is {life} needs to be involved.

• Life {general} includes all {groups of living individuals},
  
• Life {group} is any {group} of living {individual} organisms that as a {group} exhibit the ability to create more living {individual} organisms of similar form and function, even though some living {individual} organisms may lack that ability or are not selected for that function, and which, as a group, have variations and adaptations that allow some individuals to be selected over other individuals depending on fitness to the environment or fitness for reproduction.
  
• Life {individual} involves the ability to process raw materials into {molecules\assemblies} needed to repair or replace damaged, worn or non-functioning parts of the {individual organism} or to provide the energy to do such work.

Thus {individual} life does not guarantee that {group} life will exist, and {individual} life could have occurred many times before {group} life developed. Further, (general} life begins with the first {group} life but is not guaranteed to continue until there are several {group} life categories (species) such that extinction of one or more still leaves other {group} life (species) to carry on the process, and so that extinction events do not catastrophically bring an end to {general} life.

This would bridge from the previous discussion of "animate" versus "life {individual}" versus "life {group}" versus "life {general}" (ie - "life {individual}" employs "animate" chemical processes to ... etc)

Enjoy.

Edited by RAZD, : clrty

Message 19 of 77 (334223) 07-22-2006 8:20 AM

Reply to: Message 1 by Jon 07-20-2006 8:32 AM

Language and meaning are derived from utility. I think the question you need to ask (and answer) in order to answer this question is,

For what purpose am I using the word "life"?

Once you answer that question, you can come up with a definition of life that fits your purpose and see what fits in it, and what falls outside of it.

Remember, though, that your purpose for the word "life" may not be the same as the purpose of others--and thus a different word might be more appropriate than "life". Overloading definitions like that usually just leads to confusion and unnecessary arguments over semantics.

Message 20 of 77 (334224) 07-22-2006 8:26 AM

Reply to: Message 19 by Ben! 07-22-2006 8:20 AM

My impression (although it could be due to my focus on the issue) is that it is for the discussion of abiogenesis -- what is the dividing line between non-life and life or what are the lines between non-life \ animate \ individual \ group \ general life ...

Message 21 of 77 (334232) 07-22-2006 9:04 AM

Reply to: Message 17 by cavediver 07-22-2006 7:31 AM

Certainly without stars we would not have the larger atoms to build with, but even more than that, I am convinced that stars also produce molecules -- especially in their dying throes as the gases cool, the atoms 'thrown' together have opportunity, motive and method to commit formation.

I am also convince that some of these molecules are {pre-biotic\pre-organic} molecules that contributed directly to the formation of life as we know it (RAZD - Building Blocks of Life):

"So far over 130 different molecules have been discovered in interstellar clouds (2 anon 2004). Most contain a small number of atoms, and only a few molecules with seven or more atoms have been found so far. The most abundant family of molecules in the interstellar medium, after molecular hydrogen and carbon monoxide, are the polycyclic aromatic hydrocarbon (PAH) molecules. These molecules contain about 10% of all the interstellar carbon (3 Bregman & Temi).

In the farthest depths of the universe polycyclic aromatic hydrocarbon (PAH) molecules have been found by the Spitzer Space Telescope, 10 billion light-years away (4 Hill 2005). Other deep space organic compounds that have already been found are the 7-atom vinyl alcohol (5 anon 2001), the 8-atom molecule propenal and the 10-atom molecule propanal (2 anon 2004), all in interstellar clouds of dust and gas near the center of the Milky Way Galaxy, all some 24,000 light-years away - a distance so far, the molecules could not have come from earth."

But it may be even more {involved\incestuous} than that ... consider the formation of {second\plus} generation of {star\planet\debris} systems is accelerated by anything that contributes to "clumping" ... heavier atoms have higher mass to accomplish this.

But consider that {pre-biotic\pre-organic} molecules would also have increased mass and multiple ionic electrical charge areas, and thus would tend more to {interlock\bond} rather than bounce -- they may be {assistance\helpful\necessary\critical} for the early stages of planetary formation, especially considering the current thoughts on the makeup of oort cloud objects and the {pre-biotic\pre-organic} molecules in around and on comets.

Enjoy.

Message 22 of 77 (334234) 07-22-2006 9:06 AM

Reply to: Message 16 by Jon 07-22-2006 6:48 AM

I doubt that biological life just popped into existence. Before biological life there had to be some earlier proto-life systems. Maybe we could put fire as one entry in that category. A proto-life system need not have been based on DNA. Some proto-life systems could have been more capable than fire, at modifying their own behavior. And those self-modifying systems could have evolved into biological life, discovering DNA along the way.

Message 23 of 77 (334289) 07-22-2006 1:59 PM

Reply to: Message 19 by Ben! 07-22-2006 8:20 AM

This is just my feeling I don't have a developed defense of it but I suspect that it will take a much better understanding of consciousness and its relationship to matter/energy/space/time before we really move towards understanding what life is.

All the biology that is being done is very important but so much remains. The functioning chemical complexity of a cell is so staggering. Is it entirely based on chemical reactions? The function that the ancients called spirit or soul might more accurately be termed consciousness. Does consciousness have yet unrecognized roles in the function of cells? I am not speaking of the self consciousness of humans using various abstract systems but of something more elementary.

My bias is that I would like this to be the case but I don't see anyway to know if it is at present. You've been interested in this subject. I'd liked to hear your comments.

lfen

Message 24 of 77 (334384) 07-22-2006 7:41 PM

What are these "common definitions"? Can you quote them? Are they any good? Are they better than the "common definitions" according to which a whale was a fish?

A virus is alive, certainly. Prions, AFAIK, don't fall under "catalyze their own synthesis".

Message 25 of 77 (334440) 07-22-2006 11:28 PM

Reply to: Message 24 by Dr Adequate 07-22-2006 7:41 PM

See wikipedia
http://en.wikipedia.org/wiki/Life
particularly the "conventional definition
http://en.wikipedia.org/wiki/Life#A_conventional_definition

While there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life exhibits the following phenomena:

1. Organization - Living things are composed of one or more cells, which are the basic units of life.
2. Metabolism - Metabolism produces energy by converting nonliving material into cellular components (synthesis) and decomposing organic matter (catalysis). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
3. Growth - Growth results from a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter. The particular species begins to multiply and expand as the evolution continues to flourish.
4. Adaptation - Adaptation is the accommodation of a living organism to its environment. It is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolized substances, and external factors present.
5. Response to stimuli - A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. A response is often expressed by motion: the leaves of a plant turning toward the sun or an animal chasing its prey.
6. Reproduction - The division of one cell to form two new cells is reproduction. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from at least two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth.

This is reviewed by Joseph Morales on
http://baharna.com/philos/life.htm

He ends by concluding that there are degrees of life, different levels that apply.

Not to everyone, ergo NOT certainly ...
http://en.wikipedia.org/wiki/Virus

Viruses are similar to obligate intracellular parasites as they lack the means for self-reproduction outside a host cell, but unlike parasites, which are living organisms, viruses are not truly alive.

Now I would put viruses at a protolife level - they may be remnants of some first forms of life, just as life may have started with RNA before it got into DNA.

Technically viruses highjack a cell to do their work for them.

And another problem with this definition is that life (as we know it) has {elements\sections} that synthesis all the parts of the cell, not just replicate their own molecules.

Message 26 of 77 (334698) 07-24-2006 12:53 AM

Reply to: Message 23 by lfen 07-22-2006 1:59 PM

Yes, it's been a long time, but it's good to talk again after a while and catch up.

I agree with you that we're still at the stage where we're guessing--we're making progress with the simplifying assumption that everything is based on chemical reactions, but at the same time unable to know if we can account for everything that way. Seems to me the right way to proceed, but actually accepting the hypothesis at this unrefined stage is ... moving from science to philosophy it seems.

I kind of understand. I'm not sure why you use the term "consciousness" to describe this possible phenomenon. Maybe due to what you've read. But anyway, I do understand that you dont' mean the self-consciousness of humans and I have some sense of what you mean by "consciousness" from previous discussions. But not a great grasp :)

I am definitely open to the possibility of such a phenomenon. But honestly at this point I am such a pragmatist that I don't even bother wondering about the "truth" of the matter or whether the answer is knowable. If the suggestion has use, if it pushes people to have better lives, to live more in harmony with each other and their environment, then it sounds good to me. :)

I don't think there's any way to know it. And even if we are able to convincingly account for everything using explanations only from chemistry, that doesn't preclude there being some kinds of conscious forces anyway. They might operate at a super- or sub-chemical level, or they might just offer a different model with different explanatory power than a chemistry-based theory.

Which finally gets back to the topic at hand--the meaning of "life". It seems to me the desired meaning of "life" is tied so closely to a person's philosophy that it's actually impossible to be even remotely objective about it. There's never any necessity to admit anything is life. "Life" is one of those words that seem to be inextricably bound to our perceptions, rather than bound to objective measurements. Thus including or excluding entities within the word "life" would show simply a different philosophy, not an important phenomenon about the entity.

That's probably confusing. I'll leave it up to others to try and unravel it.

Ben

Message 27 of 77 (334704) 07-24-2006 1:50 AM

Reply to: Message 26 by Ben! 07-24-2006 12:53 AM

My interest in consciousness is ultimately my interest in my own subjectivity and some sort of desire to tie it to the apparent objectivity of matter/energy/space/time. The approaches of meditation are pragmatic and the other is philosophy, possibly phenomenology.

One of my suspicions is that consciousness is a fundamental property of the universe, sort of like the inside of matter/energy but it's just a hunch that makes a sort of sense to me. I don't have a great grasp of what I mean by consciousness. I think of it as what I am and it can be very hard to see the seer.

lfen

Message 29 of 77 (334716) 07-24-2006 2:21 AM

Reply to: Message 28 by nwr 07-24-2006 2:13 AM

The notion I put forward makes a certain sense to me in terms of qualia. Though I admit it's just a speculative hunch of a possibility. How do neurons give rise to the subject experience of red, or sour? I have no trouble with how vision, or taste works until the final step of the experience of it. Where does that come from?

lfen