What is the definition of life?

[PB666]

I'll mention it again, as it seems to have been missed. All those using "chemistry" in their definitions. Life as we know it, is not a chemical process alone. It requires mechanical and logical processes.

DNA is our logical operator, that stores information, and mechanical processes to read/transcribe and action it. All life has these processes, no life as we know it relies on chemical processes. Viruses included.

Try not to constrain the argument with artificial barriers, and in this case the barrier is wrong, there are a fair number of RNA viruses.

Some suspect that the origins of life lay in RNA that acted both as information and as functional entity. We actually do not know the replication basis of life prior to the last common ancestor of all life, this is a common problem in molecular paleontology (e.g. recently discovered Y in human points to an older TMRCA comparable to mitochondrial eve, and neither demonstrate the leaky species barrier between desinovans and Neanderthals).

Your approach is fallacious in nature, because DNA based cellular life likely represents the most efficient, but probably does not represent the earliest form of life. On a different world other life-forms may not have evolved DNA or nucleotide usage as on earth, in fact it is extremely unlikely they would use the same codons or the same 20 amino acids, and therefore the choice DNA or RNA may also be different. Instead of 2-amino acetic acid (glycine) as a basis it could be 3-amino propionic acids. Instead of using phosphate in the backbone of DNA sulfate or arsenate might be used. Critical events in the evolution of life very early on eventually determine the course that life takes, and some of these events may have been semi-random.

You really don't know what life is until you have studied the biochemistry and molecular biology.

Try this game out, watch the starting conditions and see what kind of structures evolve. If you play this several times widely different structures will ultimately displace everything, highly dependent on the initial starting conditions, this likely happened as and before the MRCA of all known cells appeared.

HTML5 Genetic Algorithm 2D 3-Wheelers - Chrome recommended

From a molecular biology point of view (i.e. advanced bio-chemisty) the logical process (informational) is in the structure function relationship of DNA, RNA (including the forgotten t-RNAs) and proteins, there is no contradiction, evolved life has no logic other than it is that which survives and reproduces. The t-RNA are the most important of all, because they are the keepers of the code, without which DNA is completely useless.

For example mitochondria lost almost all of their genes, they borrow heavily from their host, but they retain all the t-RNA genes, that is how important these are.

[gamowin]

Hmm, life would probably be any self replicating structures capable of adapting to their environment over time through one or many generations (evolution).

[PB666]

When it spends all of its energy storage (ATP), it will stop resisting and soon equlibirium will occur. Death.

Of course, there isn't a special "force" that makes the cell behave like that.

What about Creatine phosphate, what about NADPH?

You could have a reserve of protein sulfides in an oxygen rich environment.

You could conserve acidic in a basic or neutral environment (How mt make ATP)

There's thousands of ways to make energy depending on what a cell might have and the environment is rich in.

On a different world it could be deoxyGuanidine tri-arsenate.

Once again you think inside the box, life on other world will not duplicate the energetics on this world, because there are nearly random choices to be made, it is not likely to drift in the same directions life on earth has.

ATP on earth is intercellular energy, GTP is used for regulatory phosphorylation. It could be reversed, it could be UTP or TTP or ITP.

[Skyler4856]

I cant tell you exactly what it is, but I know it when I see it.

[KerikBalm]

I doubt that.... please refer to the edge cases already discussed, and pronounce which ones are alive, and which ones are not.

Again. I don't know what the confusion is. Sorry. Yes, there is no consensus amongst the entire world, but that's true for the colour green. Or the planet Pluto.

Ummm..... there is consensus that pluto is not a planet, and that the color green is light that activates our photoreceptors most sensitive to 534-545nm light

But both concepts can be stated scientifically.

Some concepts can be stated technically and specifically. Science is something else.

The "soul" is a concept... "god" is a concept... neither is amenable to a technical, specific, or scientific description.

Yes both have edge cases, so we can say "this specific wavelength" or "this specific sized planetoid is orbiting a star with fusion" and rule out as many edge cases as possible.

And we can talk about this specific specie of bacteria, or this specific class of RNAs...

None of that helps answer the question of what is life.

There are always edge cases. That's reality for us. But it does not stop astrophysicists, particle physicists or anyone else. We just learn what the edge cases are, and how we need to apply the information we learn from them. To either improve understanding, or change our definitions (such as with Pluto ).

Geez.... stop with the strawmen... I'm not saying lacking a definition for life stops any of this.

*Nothing* you've said comes anywhere close to answering the question of this thread "What is the definition of life"

*Nothing*

Or we can state parasitic life is parasitic, life within an ecosystem is living within an ecosystem, and rocks are rocks.

Congratualtions, you know how to construct tautologies.

Do you have any more non-sequiturs to inject into this conversation?

So, can we not ask, is a virus alive in the same way a cat is alive? Is a virus alive in the same way the cells of a cat are alive? Or is a virus only one part of life, in the same way DNA is only one part of life?

But we can also ask if a plant is alive in the same way a human is alive. Is one member of a sexually reproducing species alive in the same way a member of an asexual species is alive.

Is a non-dividing cell of a multicullular organism alive in the same way as a unicellular organism?

Is an obligate parasite alive in the same way as a free-living organism.

Is an autotroph alive in the same way as a heterotroph?

These questions are more relevant to the thread, but they still simply amount to describing differences, and can be used to sort them once you have a definition.

But we don't have a definition.

Edited July 16, 2015 by KerikBalm

[Technical Ben]

Try not to constrain the argument with artificial barriers, and in this case the barrier is wrong, there are a fair number of RNA viruses.

Interesting to learn that some viruses are RNA based. I must have missed that detail reading up on them previously.

We can make lots of suppositions on what could have been. Would we consider the suppositions for our definitions or the observations of life?

Try this game out, watch the starting conditions and see what kind of structures evolve. If you play this several times widely different structures will ultimately displace everything, highly dependent on the initial starting conditions, this likely happened as and before the MRCA of all known cells appeared.

Seen it. No idea how or what that has to do with defining observations we currently have. Can we not observe how and what a virus is, and define that? Can we not observe the same things for a bacterium, a cat etc? Then define either the process, structure or individual observation?

evolved life has no logic other than it is that which survives and reproduces.

After observing the processes involved, DNA, RNA and polymerase, I don't see how that view can hold for much longer.

Ummm..... there is consensus that pluto is not a planet, and that the color green is light that activates our photoreceptors most sensitive to 534-545nm light

Exactly! How did we reach those consensus, if not through observations?

The "soul" is a concept... "god" is a concept... neither is amenable to a technical, specific, or scientific description.

So are you saying life is such a concept? I'd say we observe it as a purely mechanical process. Other processes are based on gravitational forces. Yet others are chemical. But I see life is mechanical.

And we can talk about this specific specie of bacteria, or this specific class of RNAs...

None of that helps answer the question of what is life.

So, we can decide what the colour green really means, make a specific definition. Make it part of science. We can decide what we really meant by "planet" and adjust or remove the mistakes. Use science to decide (is it orbiting the sun, has it cleared the neighbourhood, is it even a good definition or do we need a different "name"). But we cannot for what we observe as a Cat, Dog, Bacterium or Virus? Why? Who has said so?

Congratualtions, you know how to construct tautologies.

Do you have any more non-sequiturs to inject into this conversation?

So scientific or biological categorisation is just tautological and a non-sequitur? Why attack me for pointing out we can find a benefit in categorization and naming? That everyone in science even does this? What have I done to deserve that personal attack when just talking about the subject?

But we can also ask if a plant is alive in the same way a human is alive.

Yes. Exactly. I never said this is not of benefit, or that there is no value. There are many many different types of "star". Even though there are edge cases, blurred lines we can still talk about stars. We can still define them. (Is a black hole, still a star, is a neutron star, is a gas giant. Some lack fusion, some do have a small amount, some are so close to the edge case, we must add new definitions and tests). But at no time, to we attack people for asking what the current definition and observations are, do we?

But we don't have a definition.

Sorry, many will strongly disagree with you. So we might need a better way to express why and show how that is.

Perhaps tell me about the simplest part you know of. The virus or the RNA you think is the edge case and why that is so?

Edited July 16, 2015 by Technical Ben

[lajoswinkler]

What about Creatine phosphate, what about NADPH?

You could have a reserve of protein sulfides in an oxygen rich environment.

You could conserve acidic in a basic or neutral environment (How mt make ATP)

There's thousands of ways to make energy depending on what a cell might have and the environment is rich in.

On a different world it could be deoxyGuanidine tri-arsenate.

Once again you think inside the box, life on other world will not duplicate the energetics on this world, because there are nearly random choices to be made, it is not likely to drift in the same directions life on earth has.

ATP on earth is intercellular energy, GTP is used for regulatory phosphorylation. It could be reversed, it could be UTP or TTP or ITP.

Once again, you are either trolling or not being able to understand what I was talking about. I took an example and your job was to look at the greater picture. It's you who's thinking inside the box here. It doesn't matter if it's ATP or anything else. The point was the living thing is actively resisting to change its internal environment.

It resists the change of energy and matter content. It's called homeostasis and it's the foundation of biological life. It's not an Earth thing. It's what makes life living.

[Vanamonde]

Watch the tempers, guys. Don't make it personal.

[Bill Phil]

Nope. Sorry. Look into the details. Life can exist with zero chemical processes. In fact, current life is not a chemical process, it's a mechanical one. Proteins do not fold via chemical interactions, but mechanical (atomic scale mind) ones.

Mixing the chemicals, providing the chemicals and adding energy is not enough. We have to, or life has to, physically put the building blocks into the specific place/chain/order.

Fire does not carry any information, or "multiply" (copy it's self). It spreads, but that is not a copy of it's self. Fire is like running water. Life is like a car or a house.

Life is many processes.

The process of extracting energy is chemical. The process of movement is mechanical. The process of copying DNA is mechanical and chemical.

[KerikBalm]

FWIW, Arsenate rather than Phsopahte wouldn't work for a DNA backbone... not stable in water.

There's a reason that life in mono lake hasn't evolved to use arsenic (despite what that paper claimed).

And yes, GTP, TTP, CTP, UTP, etc are also used in life, and there's no reason I can think of (off the top of my head), that life wouldn't use CTP instead of ATP, if we went back in time and "rolled the dice" again.

Even though there are edge cases, blurred lines we can still talk about stars. We can still define them. (Is a black hole, still a star, is a neutron star, is a gas giant. Some lack fusion, some do have a small amount, some are so close to the edge case, we must add new definitions and tests). But at no time, to we attack people for asking what the current definition and observations are, do we?

I'm attacking your argument. Your argument seems to be saying we can describe groups... great... we can also say what is a virus an what is a plant, just like a neutron star vs a white dwarf... etc.

That is all *completely irrelevant* to the question at hand.

Continued irrelevant arguments gets quite annoying.

So, we can decide what the colour green really means, make a specific definition. Make it part of science. We can decide what we really meant by "planet" and adjust or remove the mistakes. Use science to decide (is it orbiting the sun, has it cleared the neighbourhood, is it even a good definition or do we need a different "name")

Science does not decide. It describes and explains. Humans may decide how to make useful categories on the basis of those descriptions.

Yes, we *could* make a definition for life, but just like the distinction between a brown dwarf and a super jupiter, there would be a spectrum, and the finall division would be arbitrary.

We *can* make a definition. Congratulations...

Thats not the debate here.

The debate is basically: "what *should* that definition be?"

-and your answers are completely irrelevant to that.

Interesting to learn that some viruses are RNA based. I must have missed that detail reading up on them previously.

I'm pretty sure that has already been mentioned multiple times in this thread already, including by me.

Also, it is very well known, and a basis for the major groupings of viruses... it would be hard to read up on a subject as diverse as viruses, and miss that point, so I am skeptical that you've read up on them at all.

The common cold: RNA viruses (coronavirus, Rhinovirus)

The flu: RNA virus

HIV: RNA virus

Ebola: RNA virus

How could one miss that there are RNA viruses... as far as the human viruses you hear about the most... they're RNA viruses!

(including the forgotten t-RNAs) and proteins, there is no contradiction, evolved life has no logic other than it is that which survives and reproduces. The t-RNA are the most important of all, because they are the keepers of the code, without which DNA is completely useless.

For example mitochondria lost almost all of their genes, they borrow heavily from their host, but they retain all the t-RNA genes, that is how important these are.

Who forgets tRNAs? I certainly don't.

FYI, you need to specify *mammalian* mitochondria.

Many many mitochondria have lost various amounts of tRNAs, and instead import nuclear encoded tRNAs.

Edited July 17, 2015 by KerikBalm

[Technical Ben]

Thanks Bill Phill. That seems right.

Is it correct to say that we observe life on earth as using chemical energy in a mechanical process?

I ask as we could of cause imagine robotic life or some other form of life that follows the same processes and functions but using different chemicals or none at all (say an electric robot carrying out all the same functionality as a cell).

[PB666]

Thanks Bill Phill. That seems right.

Is it correct to say that we observe life on earth as using chemical energy in a mechanical process?

I ask as we could of cause imagine robotic life or some other form of life that follows the same processes and functions but using different chemicals or none at all (say an electric robot carrying out all the same functionality as a cell).

So one aspect of life is the instruction set they carry is basically the only set that if can pass on (with small deviations) this affords evolution and diversity. About a billion years ago sexual reproduction evolved this allow two biotes (one to create a cell with a haploid nucleus and the other to basically dump a nucleus in the cell) creating a chimera, a programmed change. Augmenting this in the prelude to microbe ..., the cells that would become haploid underwent programmed recombination in which bits and pieces of the parental derived chromosome where swapped out. This sexual reproduction with preprogrammed recombination built random chromosomal evolution into the system. Just to see how effective this is go to . . .

https://www.ebi.ac.uk/ipd/imgt/hla/stats.html (these are not stats for some exotic creature, these are the human stats, each table entry is the amount of variation for a single gene, some of these variants alleles have been carried from the time of the ancient apes forward).

This system of recombinative sexual reproduction allows for the carrying of variation in the population, it increases the ploidy, but is also provides a potential selective framework, heterozygotes versus homozygous selection that allows some genes like actin and histones to never change and other genes like HLA and KIR genes to maintain intense diversity in the population. To give an example, both the mtDNA and Y chromosome (haploid) show a time to most common ancestor in the human population of 200,000 years. The DRB1 locus shows a time to more common ancestor of 60M years.

Robots would produce clones, with the highly occasional error but with a parity bit this would be detected and corrected. Over time the robot popultion would drift to a single version and would not evolve further. To replicate evolution and to arrive at diversification and niche specialization you would need robots that could exchange information, change the information, and enter random errors and exchange those random errors with other robots.

Without this all you need is one nefarious outsider to create a robot with a virus and find a way of transmitting it and all the other robots would stop working.

- - - Updated - - -

Once again, you are either trolling or not being able to understand what I was talking about. I took an example and your job was to look at the greater picture. It's you who's thinking inside the box here. It doesn't matter if it's ATP or anything else. The point was the living thing is actively resisting to change its internal environment.

It resists the change of energy and matter content. It's called homeostasis and it's the foundation of biological life. It's not an Earth thing. It's what makes life living.

As discussed complete dormancy with an event triggered end is possible, therefore constant homeostasis is not necessary in all stage of life, just in some stages of life. Revival from homeostasis does not need ATP, it could rely on other sources of energy, which is my point. There are constraints with dormancy, in a oxidative atmosphere like ours, complete dormancy is not plausible for extended periods (millions of years), but for hydrocarbon pools deep in the earth that are protected from oxidation by high level of reductants, some biotes could maintain complete dormancy. I believe there have been papers describing how certain microbes survive in these environments were the source of oxidants appear over geological timeframes (the permissive conditions for growth once all metabolic oxygen sources - sulfate, nitrates, sugars, oxygen) have been expended.

[Technical Ben]

That's a lot of things about sexual reproduction. We would first need to prove life requires sexual reproduction for our "robot life" to require such a trait. Looking at some simple observations, life does not require sexual reproduction. So my theoretical robots don't either. (But I'm willing to hear the alternative argument)

Robots would produce clones, with the highly occasional error but with a parity bit this would be detected and corrected.

As I specified we can theoretically create a robot that carries out all the functions of a cell (that is including it's internal workings). I could for example simulate an entire bacterium or amoeba on a computer. Or alternatively, I could reconstruct it's functions in a robotic form. If my robot is constrained to error checking overrunning adaptation, then this holds true for biological life too. If biological life can find a balance between error checking and adaptation, then so could our theoretical robot made to emulate the same system.

Why am I confident of this? Because life is a mechanical processes. Any chemical systems within it can also be described mechanically for the purpose of my theoretical "robot". Thus all we need to do is decide how many functions a robot would need to have the same living capacity, as say a bacterium... right? (Note I am not asking if a robot is the same as a cat or human, as that's more functions than I could ever list )

What I need for my robot, would also be what I would test against for a definition, or a test when asking "is this other thing, perhaps on a another planet, also alive?"

Why are we confused as to "is dormancy living"? We can look at a fossil. We can look at a rock. We can look at a frog while it eats and we can look at a frog while it is frozen and dormant (I'll assume perfect suspended animation). What is the difference between these 4 things. Is it undefined and fuzzy, or can science both collect data on it, order the data, and perform tests to decide where to call them "the same" and where to call them "different" so as to label one as "a living frog" one as a "dormant frog" and one as a fossilised frog? The last being "not alive and a rock"?

Basically, we have to first decide if we are talking about the entire system or a singular part. The entire history, or the single instance in time. Yes, in the smaller measurement it is one thing (alive or dead), other the longer period of time it is both (not alive, then living, possibly later dormant, then living again, then finally dies...).

Edited July 17, 2015 by Technical Ben

[WinkAllKerb'']

life is defined by movement in contrast to immobility.

Related paradox is the inertial frame of reference to define said movement.

Annoying often observed disambiguation is.

0 up to ±≈130

+

/random more or less anoying event between and related egotist to often way to watch/feel/perceive other environemental event inacurate scale(size,time,etc.) related kind of thingies ...

(wich is accuratly 101% related to habits and knownledge transmission between generation rate this last 50 000 years for "humanity", aka too much outdated excessive conservatism in // regards with since 1900 tech/social/communication/media/"growing satelite earth perception as a planet instead a old bunch of residual old days frontier and country archaic middle ages sum related source of conflict within and between, without the above said global perception available and rising nowdays"/etc.&etc. evolution(s) exponential growth rate)

Edited July 17, 2015 by WinkAllKerb''
*shrug* +*"slighty" bored*

[magnemoe]

Thanks Bill Phill. That seems right.

Is it correct to say that we observe life on earth as using chemical energy in a mechanical process?

I ask as we could of cause imagine robotic life or some other form of life that follows the same processes and functions but using different chemicals or none at all (say an electric robot carrying out all the same functionality as a cell).

Robotic life is plausible, its simply an robot complex who is able to build copies of itself. Say complex as one robot would not work. More probably its an fabric with other robots who gather raw materials and do maintenance.

However the origin of the robotic life has to be biological.

An self replicating ship like this would be an nice way to explore the galaxy.

You send on to an nearby star, it contains an factory capable of at least build the tools you need to build an copy of the starship. So you build an comunication relay, you build probes to explore and more ships if needed before moving on. The new fabric is left and can be used to build later projects.

Then we talk about proof of life in space the definition of life is a bit redundant, a virus would prove life as it could not exist without other life. Same will go for lots of organic materials, even fossil structures might prove life.

Main problem is exotic and very primitive life. Here the replicate and use energy works well enough.

[Xannari Ferrows]

Life is sentience. Sentience is relative. Life is awareness. Awareness is variant. Life is intelligence. Intelligence is linear. Life is relative.

Life is infinite.

[Technical Ben]

However the origin of the robotic life has to be biological.

Sorry, can you explain that further? Biological has many interpretations or definitions. What would have to be the source of the robots, and why could it not be a human and/or not a human? But why would it not be biological if a human made it? (We do make copies of ourselves in a different manner already)

Then we talk about proof of life in space the definition of life is a bit redundant, a virus would prove life as it could not exist without other life. Same will go for lots of organic materials, even fossil structures might prove life.

That's not a problem with the definition. A virus would be observation of enough evidence to say other parts of life must exist to support it. It would not be an observation of life in and of it's own (but close enough for inference of such an observation).

Likewise, seeing fossils is not an observation of life, but one of fossils. It is proof of life though.

That's rudimentary, and just in our decision on the temporal terms "life/lived/living". That's not a problem with the definition or science in the slightest. We just have an additional step to decide, "is this past/present and is it active/inactive".

Yes, it's near impossible to derive if an inactive object has the capability to "live", because living is an activity... so we'd need to see it living. Then we can know if a fossil is one of life or one of something else. On earth we are familiar with the life, so can infer it from the fossils already. We can infer it from some things, but only with a lot of data (say for example a fossil of a robot would take inordinate detailed knowledge of it's parts and observation of the fossil to know if it could replicate. Again, no problem with life/fossils on earth as we have those observations already).

We don't get that in outer space, but again, that's a limit of our observations, not of the definition.

Edited July 17, 2015 by Technical Ben

[WinkAllKerb'']

1 - basically atoms are everywhere

2 - most commonly they move even if not seeable directly

3 - even if around -270 kelvin and "could appear" mostly immobile/static/inactive , universe related and changing you inertial frame of reference scaling they switch to moving/active

Definition of life is a human perception egotist nonsensical related thing (human are the everithing superior species often statistically more or less admited alike thingy and tralala god(s) belief without any disrespect in the said beliefs, just a fast way to speach scale(s) related metaphorically) ... simply ... no more no less

Edited July 17, 2015 by WinkAllKerb''

[Aanker]

Defining life is certainly not nonsensical: to begin with, life as we know it is a chemical and mechanical system centered around a few select basic atoms. This 'special chemistry' of carbon, hydrogen, etc warrants a label alone. And from there, we can add other traits that clearly define what we know as life from non-living things.

[Wallygator]

I relation to the OP - I was taught early on that the basic definition of "life" is an entity that:

1) Consumes energy

2) excretes waste

3) Can reproduce

The backdrop of a specific chemistry paradigm is irrelevant.

Maybe I've forgotten a few details over the the years...

OH yes... And that the definition of "Life" should never be commingled with the definition of "Intelligence"

I am an entity that consumes energy, excretes waste and "can" reproduce (but have chose not to) - so I probably qualify as as an example of "life".

Now as to the "intelligent" bit, Hmmm... Guess Jury is still out ;-)

[Darnok]

Anyone mentioned this one https://www.newscientist.com/article/dn25894-meet-the-electric-life-forms-that-live-on-pure-energy ?

[WinkAllKerb'']

(it's not because we're not yet able to see atoms poo and reproduce that's they don't, it's not because we're not yet able to see smaller particule that constitute atoms that they don't exist, it's not because the universe is like a molecule wandering in some random biggy primitve soup and that we're to small to see the next closest mollecule that there don't have one)

I need an apple, a plane earth and a newton ... some established belief are just boring and restrictive ... believer in thoose belief are even more boring and restricted ...

"Learn to unlearn all that you have learned" - Encyclopedia of relative & absolute knowledge - Bernard Werber -

defining life is useless ... it's everywhere ... highlight it in all it's form(s) instead of uselessly attempting to define it related to human perception(s) standard(s) ...

Edited July 18, 2015 by WinkAllKerb''

[PB666]

Anyone mentioned this one https://www.newscientist.com/article/dn25894-meet-the-electric-life-forms-that-live-on-pure-energy ?

electrons are not pure energy, and they are not unbound either, they are simply in an exploitable higher energy state. There is nothing truly peculiar about this.

The mitochondria in your cells are part of a double bi-layer membrane, they dump electrons down the electron transport chain which eventually hand the electrons off to oxygen (reducing them), and increasing the acidity in the mitochondria. The H+ pump then flow in reverse, creating ATP from ADP.

[KerikBalm]

The "H+ pump" doesn't flow in reverse.... the H+ ions flow back across the double membrane, and the ATP synthase is simiar to an ATPase running in reverse.

It may be similar to an H+ pump running in reverse, but the ATP synthase only runs one way, and the H+ gradient is not generated by it.

As to the rest... I haven't seen much in the last several post worth dignifying with a response

[Technical Ben]

electrons are not pure energy, and they are not unbound either, they are simply in an exploitable higher energy state. There is nothing truly peculiar about this.

The mitochondria in your cells are part of a double bi-layer membrane, they dump electrons down the electron transport chain which eventually hand the electrons off to oxygen (reducing them), and increasing the acidity in the mitochondria. The H+ pump then flow in reverse, creating ATP from ADP.

That they are not using external materials and chemical compounds for their energy source outside of the organism is rather new. (AFAIK, not heard it refereed to historically)

Yes, the internal workings has been known. Even some bacteria that use oxidisation as an energy source. But the article states it is knew to find out they can use the electron flow in and of it's self (If I'm reading it correctly).

- - - Updated - - -

[edit]

...What KerikBalm said, I agree.