What Defines Life: Is It DNA, RNA, or a Universal Programming?

[Skhandelwal]

I read that DNA is where life begins and therefore Viruses are hard to fight b/c they are RNA. Anyways...how is this claim supported? Aren't we programmed in certain way? Including electrons which carry information. How come everything is not a life? Or better yet, how can anything be life?

 

[Phred101.2]

Life is seen (by us who have the property of being alive), as a thing that moves around (mostly) looking for food, reproduces (copies itself), and processes external stimuli in order to have a "map" of itself and its surroundings.
The simplest concept of something "alive" is a thing that uses stored energy. It uses it to find more energy to store. This is an ongoing process, so its always a trade-off. Viruses don't carry around much energy except for the bit they use to get inside a cell or bacterium. Viruses co-opt other forms of life that follow the above general outline (they go around looking for more energy to store).

 

[jim mcnamara]

There are several slightly differing definitions of life, depending on what the guy doing the writing is dealing with.

For example, blue-green alage are considered alive by first definition definition above, but some folks would quibble about the 'stimulus' & 'moves' parts of the definition. And as Phred mentions there are things like viruses and prions that defy the first definition completely.

You'll have to learn that in Biology there is no one perfect definition for most broad terms, like 'what is life', you have to pick one that suits what you are working with, then convey it to anyone reading your work.

As long as you say 'this is my definition' and stick to it, then the most anyone else can say is:' such and such species/thing/gizmo is outside your definition'. What Phred & I showed with Phred's #1 definition. Notice we did not say it was wrong - just that it could be quibbled with: it didn't fit with viruses.

 

[Phred101.2]

You could say that having stored energy is a necessary condition, but it needs to use it both to store more, and (if it can), move around. Some things seem to be only like an arc of the "life" circle.

 

[jim mcnamara]

Quibble: I'm not sure you could say that prions store energy.
The $$PrP^{sc}$$ protein acts as a catalyst or maybe enzyme, to transform
$$PrP^{c}$$ into $$PrP^{sc}$$

I'm not also sure that prions are life anyway.

 

[mgb_phys]

As jim says - it depends on who you ask.
Chemists talk about respiration and energy. Maths/CS people talk about inheriting characterstics. The definition about having DNA is a bit circular - if aliens turned up with TNA they would still be alaive.

Not sure if prions/enzymes can pass-on favourable characterstics and so be considered alive.

 

[Skhandelwal]

Aren't these opinions? What the factual theories in existence considering this issue?

 

[Phred101.2]

Fact 1. Life uses energy
Fact 2. Life stores energy (storing energy requires energy)
Fact 3. Life reproduces itself (this uses energy)
Fact 4. Life maintains some 'map' of itself and its environment (this requires energy too)
Fact 5. Some life is mobile. (guess what mobility requires)

 

[AppleBite]

I would just like to modify the use of the word "mobile" into "responsive".
Not all forms of life are mobile (except when they grow in size) but what is meant by the term mobile is that a living organism has to be responsive to external stimuli.

 

[jim mcnamara]

Skhandelwal -

What you are seeing is exactly what you were told. It is not opinion, although it looks kinda like we are just throwing stuff out there.

Do you understand Math? If you know what the Axiom of Choice is, then you will understand what is going on here. There is a theorem - Goodman's Thoerem.

Goodman proved that if the axiom of choice vx3yA(x, y) ->
3fVxA(x, f(x)) is added to intuitionistic arithmetic (here
x, y9 and / are functionals of finite type), then no new arithmetic
theorems are obtained.

This is basic Math. The idea is that accepting or rejecting certain Axioms gives you different results - or not. We are essentially defining biological postulates, not voicing opinions necessarily. Read about Koch's postulates which define what is required to demonstrate the existence of a pathogen.

It is NOT opinion. It is the fact that it's diffcult to create a definition of life that always works because the huge number of weird things we find over time. Nobody really knew about prions or even suspected them prior to 1975, for example. They bent the rules.

 

[Skhandelwal]

So what you guys are trying to tell me is that we don't have an exact definition of life...the more life we discover, the better our definition gets. However, so far, scientists make us look "superior" to nonliving things b/c we have the ability to make a choice. But may be, we don't make choices at all...we are programmed that way in our DNA.

 

[jim mcnamara]

S -

Yes, you got it. I don't know if defintions get "better" or not but they do change. Your idea of better may not be what mine is.

 

[Phred101.2]

But may be, we don't make choices at all...we are programmed that way in our DNA.

Skhandelwal: this issue is something we still can't really say too much about. Except that we know neurons grow and connect to other neurons, and this is 'controlled' by signalling molecules -ultimately DNA 'produces' a neuron's environment but a neuron is also affected by the external world...

 

[ganstaman]

I read that DNA is where life begins and therefore Viruses are hard to fight b/c they are RNA. Anyways...how is this claim supported? Aren't we programmed in certain way? Including electrons which carry information. How come everything is not a life? Or better yet, how can anything be life?

I may have missed it, but I didn't see anyone make this correction yet. Viruses don't all have RNA. They can have DNA too (like HepB, for example). And that's hardly what makes them hard to fight -- I thought it was more that viruses are basically parasites feeding off our cells, so 'killing' them is hard to do without killing our own cells.

Also: Viruses may or may not be life. We may or may not have free will.

 

[Eshi]

I'm only a high school student, but having recently studied the nervous system I would have to say that there is free will, if free will is defined as the ability for the brain to analyze senses and make create different options, in some cases each with a probability of living, for example if u are on the edge of a cliff, and you look down, ur eyes perceive the depth and height at which you are and this information is transmitted to ur CNS(i'm pretty sure that this isn't an automated response) and you have the choice of going closer, which increases ur probability of falling(which is going to equal death in this hypothetical situation) and backing off which will increase ur chances of survival. So now u make the choice of stepping back, if u did the opposite you are taking a risk factor. Which surprisingly is also a tendency that humans have, since evolutionary speaking living things must take risks to survive sometimes(this tendency is what drives gambling addictions and the rush u get when u win). Now the only reason why you might step forward is because of an advantage you would gain from doing this, such as respect from the community(i.e. your friends being impressed with you). If there is no advantage, then you brain will tell you to back off, and if you do the opposite that usually means ur crazy. I would consider this free will, because u do have the choice. Free will really comes into play in situations where there isn't an advantage, such as taking a left or right at an intersection(and you u don't know where either leads), where u just have to guess, and that is what free-will really is, the ability to take risks and adapt

Hope this isn't too off-topic, kinda was just inspired to write after the last few posts. Everything i said of course can be debated, most advanced brain functions are still being researched more fully, so its tough to say anything about the 'big' questions. I also agree with post #8 by Phred and #9 by Applebite

 

[Phred101.2]

Right. Free will is something we perceive ourselves (and other forms of life) as having because it is an advantage to be able to choose (between chasing your lunch or waiting somewhere for it to come to you, for example). Or alternatively, life is compelled to do this (there is no choice), but this is because life needs to learn about things...

 

[ganstaman]

I'm only a high school student, but having recently studied the nervous system I would have to say that there is free will, if free will is defined as the ability for the brain to analyze senses and make create different options, in some cases each with a probability of living

I'm not really sure if that's how most would define free will. The argument against free will is that when the brain is "analyzing" and "creating options" all that's going on is some chemical reaction and some electric forces being passed around. It's not a "soul" that is doing the thinking, it's just a sac of chemicals acting solely on the laws of physics and chemistry.

If I make a robot that can sense its environment and create different options for how to react to what it senses, does it then have free will? Absolutely not -- it simply follows exactly what I programmed into it. That the brain is more complex to the point where we can't fully know what's going on doesn't mean that it's not analagous to my robot's software.

 

[Eshi]

If I make a robot that can sense its environment and create different options for how to react to what it senses, does it then have free will? Absolutely not -- it simply follows exactly what I programmed into it. That the brain is more complex to the point where we can't fully know what's going on doesn't mean that it's not analagous to my robot's software.

Yes, i agree with you, that's because robots do a linear process form(i.e. sense --> analzyze --> respond(action)) and the human mind is a cyclic cycle, right? So that means humans will sense something like heat and move away, then sense some more and continue doing this cycle. whereas the robot would just sense the fire move away and be done with that process. So the robot separates each process and the human kinda integrates multiple processes together and puts them on repeat?

 

[Phred101.2]

There is a sense, or an apprehension we have of "something" that does the thinking. Except of course, we can view thinking as a response, rather than a 'self-initiated' process by some "independent" being. This last (which is pretty much the classical view) then begs the question: where is this independent self? What is behind it (is there a higher "self of selves", and etc.)?
I personally think that this sense we have (of being independent of our thinking) is due to our advanced brain, which has so much circuitry that we have the capacity, unlike most other animals, to diverge from immediate concerns, and think (a lot) about things that aren't to do with finding food, or shelter, or getting a fire going, or any of the ongoing tasks that life requires. Once we started to just think, for the sake of it, we diverged from the usual environmentally-directed thought patterns, and learned to philosophise. This explains our belief in our 'free' ability to think and act because of it, rather than just responding (but it's probably an illusion).

 

[DaveC426913]

Life
1] metabolizes - consumes fuel and excretes waste
2] reproduces - makes copies of itself
3] responds to external stimuli
4] grows

 

[Phred101.2]

1) To "consume fuel", it needs a store of energy
2) Reproduction is an energy-using process
3) Responses to stimuli involve energy use
4) Growth is the "conversion" of energy to cellular material (proteins, carbohydrate stores, etc.)
Conclusion: life is something that stores energy and uses it for all of the above...

 

[DaveC426913]

1) To "consume fuel", it needs a store of energy
2) Reproduction is an energy-using process
3) Responses to stimuli involve energy use
4) Growth is the "conversion" of energy to cellular material (proteins, carbohydrate stores, etc.)
Conclusion: life is something that stores energy and uses it for all of the above...

While true, it does not exclude things that are not life. Basically, what you've defined is the set of energy-using systems of which life is a subset.

It does not serve as a useful definition.

 

[ganstaman]

Yes, i agree with you, that's because robots do a linear process form(i.e. sense --> analzyze --> respond(action)) and the human mind is a cyclic cycle, right? So that means humans will sense something like heat and move away, then sense some more and continue doing this cycle. whereas the robot would just sense the fire move away and be done with that process. So the robot separates each process and the human kinda integrates multiple processes together and puts them on repeat?

I may be misunderstanding you, but I think my answer is: no.

I think you're making a distinction that doesn't exist. Robots and humans sense, then analyze, then react, and then repeat it all. Why would you say the robot isn't integrating these? Does the robot stop sensing the heat once it moves away from the fire once?

 

[Phred101.2]

1) To "consume fuel", it needs a store of energy
2) Reproduction is an energy-using process
3) Responses to stimuli involve energy use
4) Growth is the "conversion" of energy to cellular material (proteins, carbohydrate stores, etc.)
Conclusion: life is something that stores energy and uses it for all of the above...

While true, it does not exclude things that are not life. Basically, what you've defined is the set of energy-using systems of which life is a subset.

It does not serve as a useful definition.

You mean things like batteries that store energy, or cars or robots? These do not respond to stimuli the same way. A robot cannot learn (they only respond in a preprogrammed way) and evolve due to the accumulation of ¨learning¨ (DNA modifications or mutations -group knowledge). How many robots can reproduce or grow? I´m sorry, but your blanket statement does seem a little trite, at least.

Why would you say the robot isn't integrating these

What does this integration represent? Is it an equivalent of what some organism does (say a blue-green alga), when it measures something (say the light near the water´s surface)?

 

[DaveC426913]

You mean things like batteries that store energy, or cars or robots? These do not respond to stimuli the same way. A robot cannot learn (they only respond in a preprogrammed way) and evolve due to the accumulation of ¨learning¨ (DNA modifications or mutations -group knowledge). How many robots can reproduce or grow?

The fact that life stores energy to do its functions is incidental (i.e. of little use) to its definition (since many things store energy for their functions).

It is those functions that makes life unique, and thus define it from cars and batteries and robots.

 

[Phred101.2]

The fact that life stores energy to do its functions is incidental (i.e. of little use) to its definition

You think? I would say that because life is obliged to store energy and use the store to find more energy (to store), defines it pretty closely. It has to grow (extend), and perhaps move around to do this. Also it necessarily must be able to determine (discriminate or measure) its environment to do this, and measure its own internal ´environment' simultaneously. Bacteria do this. Learning is the accumulation of this measurement and discrimination, and storage of this too (in DNA and protein). How does a car or a battery or a machine -a robot, do this?

 

[DaveC426913]

I have 47 gadjillion distinct objects on a (large) tray and I want to separate them into life and non-life. (The act of separating the two is the embodiment of having a definition. If we have a non-ambiguous definition of life vs. non-life we can do this, if we do not, we cannot.)


I keep all things that (metabolize and reproduce and grow and respond) on the tray, and toss everything else off the tray. I have 11 brazillion objects left.

I decide to enact your criteria and (from the remaining 11 brazillion objects) remove all that do NOT store energy for these functions.

How many do I have left? Exactly 11 brazillion.

"Storing energy" does not contribute to our isolating the set of things that are life from the things that are not life. Thus it is an irrelevant criteria in defining life vs. non-life.

 

[Phred101.2]

"Storing energy" does not contribute to our isolating the set of things that are life from the things that are not life. Thus it is an irrelevant criteria in defining life vs. non-life.

So there is no way to distinguish a battery or a jar full of some chemicals (that have a potential energy say, if someone opens the jar and chucks a lit match in), from a bacterial culture? There is no way to tell if a bit of wood or a rock is alive or not, because containing energy is an irrelevant distinction? How do you personally decide if something, say, is not alive? Just for argument´s sake, what criteria do you look for?

I keep all things that (metabolize and reproduce and grow and respond) on the tray

How can you hope to determine that things are metabolising or reproducing, for example, surely this must be impossible?

Frankly I think you are completely wrong, actually incorrect, and you definitely need to review what you know about this subject (you´re talking rubbish, in other words).

1. Things contain or store energy. All things made of matter can be converted to some kind of energy.
2. Life stores energy. It has to use energy to do this.
3. Life uses energy to find more energy, things can store energy (have or contain some), but only life (is obliged to) goes around looking for more of it. All by itself.
4. Life tracks its environment by using energy to maintain a map of external and internal information
5. Life grows (extends itself) by converting energy into more ´life´.
6. Life reproduces, this requires energy.
7. Life shares information with others. This sharing is not an energy-free process.

 

[DaveC426913]

So there is no way to distinguish a battery or a jar full of some chemicals (that have a potential energy say, if someone opens the jar and chucks a lit match in), from a bacterial culture?

?

Of course there is - the four criteria defined: metabolism, reproduction, stimulation and growth.

 

[DaveC426913]

1. Things contain or store energy. All things made of matter can be converted to some kind of energy.
2. Life stores energy. It has to use energy to do this.
3. Life uses energy to find more energy, things can store energy (have or contain some), but only life (is obliged to) goes around looking for more of it. All by itself.
4. Life tracks its environment by using energy to maintain a map of external and internal information
5. Life grows (extends itself) by converting energy into more ´life´.
6. Life reproduces, this requires energy.
7. Life shares information with others. This sharing is not an energy-free process.

Again, I am not saying these things aren't true, I'm simply saying that the "uses energy" part doesn't help to distinguish life from non-life.

Take #6 for example:
"Life reproduces, this requires energy."

Do you know of any circumstance in the universe where a process "reproduces" without "requiring energy"? If there are no processes that reproduce without requiring energy, then this criteria does not narrow the choices by any. After applying it, you have the same number of items on your tray as you had before.


Or #4:
"Life tracks its environment by using energy to maintain a map of external and internal information"

Do you know of any process in the universe where a system "tracks its environment to maintain an external and internal map" - but does NOT "use energy" to do so? If you do NOT know any, then this criteria does not help narrow the definition any. same items on tray.

Simply put, you are confusing properties of life with definitions of life. What you are listing is properties that life has. But those properties do not help narrow the definition of life.