The question of what is life came up over coffee this morning. It is actually not that easy to put a finger on. Some things we have no hesitation in calling alive – like ourselves. With others it is less obvious.
In my first ever biology class at school, I was taught that there were seven characteristics of life, which if memory serves me right include the fact that life has to feed (acquire building blocks), move, grow, respire (produce energy) be organised into cells, be sensitive to the environment and be adaptable. I would also add that it has to locally reverse entropy too.
So, we all do these things, but are they universal? Viruses for example don’t grow or move. They don’t even respire in the sense that they make their own ATP. They get that from their host cells. They are not cellular in nature and are only adaptable in the sense that mutations can occur – they can’t adapt in the sense that a Venus flytrap can turn on antifreeze proteins when they are chilled. So, are viruses alive? They do reverse entropy and appear sensitive to the environment in that some can use cues inside the host cell to reproduce – Herpes for example lies latent for long periods of time.
So, are viruses alive?
Many invertebrate embryos are not initially cellular either – they are syncitial (no cellular divisions between nuclei). Slime Moulds also spend much of their lives in a syncitial state too.
What about salt crystals? It can grow by reversing entropy. Split them in two and given the right conditions, they can grow into two new crystals. It is sensitive to the environment; it “knows” when to grow and when to dissolve. Its component parts have all the information needed to produce an identical crystal, and is organised into unit cells, so is it alive?
Discuss!
In my first ever biology class at school, I was taught that there were seven characteristics of life, which if memory serves me right include the fact that life has to feed (acquire building blocks), move, grow, respire (produce energy) be organised into cells, be sensitive to the environment and be adaptable. I would also add that it has to locally reverse entropy too.
So, we all do these things, but are they universal? Viruses for example don’t grow or move. They don’t even respire in the sense that they make their own ATP. They get that from their host cells. They are not cellular in nature and are only adaptable in the sense that mutations can occur – they can’t adapt in the sense that a Venus flytrap can turn on antifreeze proteins when they are chilled. So, are viruses alive? They do reverse entropy and appear sensitive to the environment in that some can use cues inside the host cell to reproduce – Herpes for example lies latent for long periods of time.
So, are viruses alive?
Many invertebrate embryos are not initially cellular either – they are syncitial (no cellular divisions between nuclei). Slime Moulds also spend much of their lives in a syncitial state too.
What about salt crystals? It can grow by reversing entropy. Split them in two and given the right conditions, they can grow into two new crystals. It is sensitive to the environment; it “knows” when to grow and when to dissolve. Its component parts have all the information needed to produce an identical crystal, and is organised into unit cells, so is it alive?
Discuss!
20 comments:
I may play devils advocate here just for the hell of it :-)
I have been thinking about this a lot recently. I don't think the term "life" has any useful meaning. It is simply complex structures that arise in far-from-equilibrium situations that can replicate.
I don't think crystals qualify. I think viruses do; they're life, but simply very weird life.
I freely admit this is just my personal opinion, and isn't backed up by much!
Interesting fact about the Venus Fly Trap: I didn't know that. Fascinating.
Damn biology questions and I've not even had my morning coffee.
Is there anything wrong with the definition that life is self-replicating chemistry? (I try and keep my biology simple)
Molecules that 'react' in an environment to produce more molecules that looks like itself?
I’ll get my coffee now... crap instant muck that it is (erm... I wonder if my dirty cup has evolved life over night? I hope it survives boiling water)
Lee
Steve It is simply complex structures that arise in far-from-equilibrium situations that can replicate.
I think that is what I meant...
Lee
I agree Steve. I dont think there is much other than replication and reversal of entropy that you can add.
Viruses are what I would describe as "simple" chemistry, however they cant replicate themselves. They need a lot of help from host machinery. Does this make them different to other parasite?
You kind of "feel" that salt crystals are not life, but they contain some of the characteristics of organisms - they can even "heal" damage given the right conditions. Just like any other species, they need the right conditions.
What Is Life?
Sorry, this song has been going around my head all day and since it is Billy's fault, I thought I would share it here.
http://au.youtube.com/watch?v=0Jy4tMySp5o
I didn't say I liked the song...
Lee
Arrggggghhh, Noooooo!
I was actually going to call it "I wanna know what life is" but couldn't get foreigner oot ma heed afterwards.
By the way, I've just found out that the real capital of Iceland is not Reykjavik. It is actually £3.50. I blame having to support Kerry Katatonia myself
Lee
I thought I would share it here.
Ta! :-)
When software eventually passes Turing's test, will it be life?
When software eventually passes Turing's test, will it be life?
Does life have to be intelligent?
That reminds me of bart simpson asking his sunday school teacher if robots get into heaven. She replies no, then Bart asks if a robot with a human brain would get into heaven
Does life have to be intelligent?
Nope
What about the software?
What about the software?
Squat down and make your case
Billy Arrggggghhh, Noooooo!
Sorry, but you started it... :-)
I been singing the song all day today as well - but the wife has never heard of it? How?
Lee
but the wife has never heard of it? How?
She was one of the lucky ones then
Computer viruses find a host, evade the host's defences and then replicate then find another host to attack. That seems pretty lifelike.
I don't know if this is adequate or not. Biology is not my strong suit.
You seem to do quite well :-) I really is a tough one even for a biologist. There are exceptions to most of the characteristics. If we stick to the seven in the post, we do have to exclude viruses and probably some bacteria too. However, why should boundries be clear cut. That is the way creationits would have it.
Isn't there a programme that attempts to act like a human on blogs etc?
Rune, More a question from my ignorance, but do computer viruses reverse entropy? It is a very interesting point though.
If we take it further and look at it in a selfish Darwinian way, who is the virus serving? Itself or the programmer? (now we are getting onto the idea of god)
Elbot does seem a bit random, but sounds like some people I have come across - like spiritual mysticists
do computer viruses reverse entropy?
I wonder how they could? They are stuck inside a machine that is heating up the room...
I wonder how they could? They are stuck inside a machine that is heating up the room...
I wonder if we should reconsider the need to reverse entropy?
However, that would require defining computer viruses as life. I'm still not convinced they are.
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