Does life have to be Biochemical?

[magma]

Would Aliens require oxygen to generate themselves ATP as energy?

[Doodler]

Atp?

[Swift]

magma

I take those two questions "Does life have to be biochemical" and "Does life need ATP" as two very different questions.

I suspect, though I'm not sure, that there are life forms on Earth that don't use ATP. Even if not true, it seems easy to imagine life that didn't, there are a lot of biochemical cycles that one might use.

Does life have to be biochemical.... are you talking about an inorganic lifeform (silicon?) or something made of energy? There are previous discussions of both of these around this thread.

[magma]

Atp?

Adenosine triphosphate.

Swift - i would like to know if life elsewhere has to be biochemical to function. Can there possibly be cars/ robots that 'live' if they were synthesised in a way (e.g. we obtained chemical info from non-biochemical species and made a car from it). Forgive me if i'm not making sense.

[Swift]

Swift - i would like to know if life elsewhere has to be biochemical to function. Can there possibly be cars/ robots that 'live' if they were synthesised in a way (e.g. we obtained chemical info from non-biochemical species and made a car from it). Forgive me if i'm not making sense.

I don't know. Carbon-nitrogen-oxygen-hydrogen chemistry is just so darn useful and versatile (and this is coming from an inorganic chemist!). Just look at all the compounds humans have made from them. While one can imagine life based on something like silicon, it just doesn't make as many different kinds of things.

As far as naturally occurring lifeforms that were like robots, it is very hard for me to imagine how such a thing would come about, but maybe that's just my lack of imagination. Could a synthetic lifeform like that exist (think Data or Hal) - yes I can imagine that. But someone (or something) would have to build it.

[BioSci]

Would Aliens require oxygen to generate themselves ATP as energy?

to answer the two questions:

"Does life have to be biochemical?" this is a "circular" question since the definition of Bio-chemical means the chemical reactions that are involved with living organisms. Therefore, if you define something as living - its chemical reactions will be "biochemical".
Perhaps you mean "will alien life have the same biochemical reactions as Earth life?" The answer to that question is unknown since we do not have any evidence for what alien life will be like. But we can guess that alien life is most likely to include some similar "biochemical" reactions but also biochemical reactions that may be quite different. It is highly unlikely that our biochemistries would be "compatible" (that is, we would not be edible nor would they be edible)

"Would Aliens require oxygen to generate themselves ATP as energy?" The answer is no - even on Earth there are organism (anaerobes) that do not require oxygen to generate ATP.
Although all known Earth organisms do use ATP, it is unlikely that an alien organism would actually use ATP. Even if they had a similar biology, the odds are that they would have developed using a different "high-energy" molecule - and even if they used a triphosphate, it is more likely that it would use some other nucleotide as the base molecule - simply on a statistical basis.

[Swift]

Thanks BioSci. So all Earth organisms use ATP, even anerobes (learn something new everyday). I suppose there is speculation on when in the history of life on Earth organisms started to use ATP. Are there ideas about what was used before?

[Van Rijn]

to answer the two questions:

"Does life have to be biochemical?" this is a "circular" question since the definition of Bio-chemical means the chemical reactions that are involved with living organisms. Therefore, if you define something as living - its chemical reactions will be "biochemical".

I suppose it would be difficult to avoid chemical reactions, but we can imagine something along the line of macroscopic machine replicators that might well process materials in bulk similar to today's industrial processes, and where many life functions were mechanical and electrical in nature. Something like that might require a different classification.

[BioSci]

Thanks BioSci. So all Earth organisms use ATP, even anerobes (learn something new everyday). I suppose there is speculation on when in the history of life on Earth organisms started to use ATP. Are there ideas about what was used before?

Any such speculation is just so ... speculative.

There are a number of hypotheses regarding how the various biochemical pathways and molecules developed including the use of ATP. The problem is that any hypotheses on abiogenesis are very difficult to test and remain very specualtive.

[BioSci]

I suppose it would be difficult to avoid chemical reactions, but we can imagine something along the line of macroscopic machine replicators that might well process materials in bulk similar to today's industrial processes, and where many life functions were mechanical and electrical in nature. Something like that might require a different classification

Yes, and perhaps the first classification question may be: "Is it living?"

[Van Rijn]

Yes, and perhaps the first classification question may be: "Is it living?"

Assuming a complex system could self replicate in a natural environment, why wouldn't it be considered living?

Edited to add:

Assume this is a complex organized system, it processes energy and materials for itself (metabolism), can respond and adapt to the environment, can repair itself and can replicate based on a detailed stored pattern, but is essentially mechanical/electronic based.

[BioSci]

Assuming a complex system could self replicate in a natural environment, why wouldn't it be considered living?

Edited to add:

Assume this is a complex organized system, it processes energy and materials for itself (metabolism), can respond and adapt to the environment, can repair itself and can replicate based on a detailed stored pattern, but is essentially mechanical/electronic based.

Good question and one that is not simply answered.

From Wiki:

A conventional definition

Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life exhibits the following phenomena:
1. Homeostasis: ...
2. Organization: ...
3. Metabolism: ...
4. Growth: ...
5. Adaptation: ....
6. Response to stimuli: ...
7. Reproduction: ...

Note that this definition includes the disclaimer that it is limited to a "biological manifestation". Most likely to differentiate from things like storms, flames, software, etc.

If some sort of "organism" met your criteria - it might be considered "alive" - or "just a robot?"

[Ronald Brak]

I'll mention that people have made simulated life inside computers. They anabolize and catabolize (make stuff and break stuff) in their electronic worlds and I'm tempted to count them as alive, if only to score brownie points with our future electronic masters.

[Van Rijn]

Heh. I was thinking about software, though I think current examples are too simple. In his "Uplift" universe, David Brin had these "physical" designations for known life forms: Oxygen-breathing, hydrogen breathing, mechanical, memetic, and quantum. (For civilization types, there was also "retired" and "transcendent.")

Of course that's fiction, but I have this image of a mechanical species debating whether greasy waterbags full of complex chemicals could be considered alive. However things turn out, the question of a careful definition of life is indeed a hard one to answer, and is likely to get much harder.

[weatherc]

Of course that's fiction, but I have this image of a mechanical species debating whether greasy waterbags full of complex chemicals could be considered alive.

Which brings us to Bisson's short story, "They're Made out of Meat" which has been discussed on this board before.

[eburacum45]

I have only read one Uplift novel; how do 'memetic' lifeforms operate? Are they, as I suspect, the equivalent of computer viruses? That is quite a nice distinction.
In some ways memes (as defined by Dawkins) themselves could be considered self-replicating entities in a culture; perhaps memes could evolve to such a level of sophistication (by 'survival of the most believable') until they are self-evidently separate entities.

[Dr Nigel]

Good Note that this definition includes the disclaimer that it is limited to a "biological manifestation". Most likely to differentiate from things like storms, flames, software, etc.

If some sort of "organism" met your criteria - it might be considered "alive" - or "just a robot?"

Additionally, many biologists include that something alive would have a boundary of some kind, which mainly serves to distinguish presently-known organisms from other natural phenomena that could meet the other aspects of the definition. Or, in other words, a clarification of the "biological manifestation" aspect of Wiki's definition of life.

Although, if you think about it, the term "biological manifestation of life" is a tautology and does not actually help to clarify anything.

[Van Rijn]

I have only read one Uplift novel; how do 'memetic' lifeforms operate? Are they, as I suspect, the equivalent of computer viruses? That is quite a nice distinction.

A bit more than that. In his stories, they are "life" that can operate in logic or minds of other lifeforms, or in "E space" (some dimension or hyperspace).

I found a sample on his website that has one scene with a sentry operating in E space:

http://www.davidbrin.com/heavensreachsample5.html

[springa]

I think that mechanical and "memetic" life is quite possible, but wouldn't any such life have to be originally created by a chemical/biological lifeform? I can't imagine how such a life form could arise on its own without lots of manipulation by an already-existing intelligent lifeform. Then again, as a previous poster commented, this may just show the limits of my imagination!

The biggest problem with all speculations about life beyond the earth is that the only life that we have solid facts about is earth life. We're trying to guess the nature of life in many different parts of the universe based on a representative sample of 1 planet. Any statistician will tell you that a representative sample of 1 is not something that you can use to draw reliable conclusions about a large group.

[Amber Robot]

Carbon-nitrogen-oxygen-hydrogen chemistry is just so darn useful and versatile (and this is coming from an inorganic chemist!).

Not to mention that they are the most common elements in the universe!

[eburacum45]

Mechanical-synthetic lifeforms might need to be created by biological creatures like ourselves, but once created they might prove to be more versatile and capable of replicating in more diverse environments than biological life. It may easily be the case that the most common form of self-replicating complexity in the universe is mechanical in nature, robots and Von Neumann machines created by a billion dead civilisations.

Can such a form of self-replicating complexity arise spontaneously? Geological processes create some remarkably complex structures under different circumstances; could it be that occasionally a simple mineralogical self replicating entity arises, one with the capacity to evolve into more complex forms? It seems very unlikely, but it would be interesting to be proved wrong.

[Thanatos]

Can't help but wonder if somewhere 'out there' are sentient machines who speculate they are ancestors of primitive nanites produced by chance collisions between nickel iron meteors and mineral deposits. Of course, they would reciprocate their EM sensors in derision at the notion the chemically engineered molecular systems they create to produce fuels and building materials could arise spontaneously.

[Dr Nigel]

Not to mention that they are the most common elements in the universe!

Er ... yes, also Helium, which is the second-most common element after hydrogen, but is not so useful to life, being chemically inert.

[Dr Nigel]

I don't know. Carbon-nitrogen-oxygen-hydrogen chemistry is just so darn useful and versatile (and this is coming from an inorganic chemist!). ...

Yes, but life as we know it could not get by without also having access to sulphur and phosphorous.

[bindegal]

Can't help but wonder if somewhere 'out there' are sentient machines who speculate they are ancestors of primitive nanites produced by chance collisions between nickel iron meteors and mineral deposits. Of course, they would reciprocate their EM sensors in derision at the notion the chemically engineered molecular systems they create to produce fuels and building materials could arise spontaneously.

LOL

I really like that thought, and why not?

[Romanus]

<<Would Aliens require oxygen to generate themselves ATP as energy?>>

Probably not; then again, anaerobic ETs would probably live an extremely lethargic existence compared to us crazy oxygen-burners.

[greenfeather]

Would Aliens require oxygen to generate themselves ATP as energy?

As to whether life has to be biochemical...I'm reading the coolest book, THE SUNBORN by Gregory Benford. It portrays these plasma intelligences that live in the space beyond the solar system (and thru most of the galaxy). "They live through the adroit weaving of electrical currents.They feed on the electrical potentials that trickle through the comet clouds. Their interiors are highly ionized plasmas...."

These Beings tell strange tales of "the little rocky worlds that have been lately rotting into life." "A low obscene hot life. SOLIDS. Not powered by the clean transformations of electromotive force, but by the clumsy building up and tearing down of molecules."

This is some great prose!! And it makes you think: there is so much energy, heat and power in space, could something have evolved that can use that power? Also, when you think about molecular processes like the breaking down of the glucose molecule and the creation of ATP... those are some awfully clumsy processes. Who knows, maybe there are other processes going on.

[Dr Nigel]

Who knows, indeed?

I have to say, it would be extraordinary indeed if lifeforms existed that were composed of rarefied plasma. How would they maintain structural integrity?

[Amber Robot]

I have to say, it would be extraordinary indeed if lifeforms existed that were composed of rarefied plasma. How would they maintain structural integrity?

Magnetic fields?

[greenfeather]

Who knows, indeed?

I have to say, it would be extraordinary indeed if lifeforms existed that were composed of rarefied plasma. How would they maintain structural integrity?

Um...electromagnetics? Gravitational flows? (we're talking large beings here. Larger than planets.

We'd better ask Greg Benford, the author. Matter of fact there was a thread here about plasma life. Apparently plasma can form membrane-like bubbles.