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What is life?

PostPosted: May 12th, 2017, 8:02 pm
by Alan McDougall
What is life?

Give your best short definition of what life really is below.

Re: What is life?

PostPosted: May 12th, 2017, 8:18 pm
by TheVat
viewtopic.php?nomobile=1&f=37&t=6722

A fairly extensive SCF discussion on this question. I haven't reread it, so can't totally vouch for its usefulness, but perhaps worth a look?

Re: What is life?

PostPosted: May 13th, 2017, 4:04 pm
by Alan McDougall
Braininvat » May 13th, 2017, 2:18 am wrote:http://www.sciencechatforum.com/viewtopic.php?nomobile=1&f=37&t=6722

A fairly extensive SCF discussion on this question. I haven't reread it, so can't totally vouch for its usefulness, but perhaps worth a look?


The "Cambrian Explosion" refers to the sudden appearance in the fossil record of complex animals with mineralized skeletal remains.

It may represent the most important evolutionary event in the history of life on Earth.

The Cambrian explosion makes one suggest that the theory of evolution is not 100% correct?

Re: What is life?

PostPosted: May 13th, 2017, 4:06 pm
by DragonFly
Life is of metabolism in a system not in equilibrium.

Re: What is life?

PostPosted: May 14th, 2017, 3:52 am
by Alan McDougall
DragonFly » May 13th, 2017, 10:06 pm wrote:Life is of metabolism in a system not in equilibrium.


We exist as living beings on a knife edge of conditions and if just one of them goes out of wack we die.

Re: What is life?

PostPosted: May 14th, 2017, 6:28 am
by BioWizard
Alan McDougall » 14 May 2017 02:52 am wrote:
DragonFly » May 13th, 2017, 10:06 pm wrote:Life is of metabolism in a system not in equilibrium.


We exist as living beings on a knife edge of conditions and if just one of them goes out of wack we die.


I don't know if I can agree with this. Our bodies will adapt in all sorts of ways and will try to keep us alive under extreme environmental and health conditions. People survive all sorts of crazy stuff all the time. Biology is quite robust and not the fickle balance on a knife's edge you seem to think it is.

Re: What is life?

PostPosted: May 14th, 2017, 12:38 pm
by Alan McDougall
A candle or even a crystal could be taken as a form of life?

Re: What is life?

PostPosted: May 14th, 2017, 12:53 pm
by BioWizard
Alan McDougall » 14 May 2017 11:38 am wrote:A candle or even a crystal could be taken as a form of life?


Not really.

Re: What is life?

PostPosted: May 14th, 2017, 4:44 pm
by doogles
Life is a coordinated series of electron shifts mediated by enzymes under gene control.

Re: What is life?

PostPosted: May 19th, 2017, 10:50 am
by Eclogite
Alan McDougall » Sat May 13, 2017 8:04 pm wrote:The "Cambrian Explosion" refers to the sudden appearance in the fossil record of complex animals with mineralized skeletal remains.

It may represent the most important evolutionary event in the history of life on Earth.

The Cambrian explosion makes one suggest that the theory of evolution is not 100% correct?
I thought I would use my 'please select your preferred answer on this one', so here goes.

Please select your preferred answer from the following responses:

1.The Cambrian explosion appears sudden, but in many respects it is not. The Eocardian fauna predate it, for example. Other examples exist. Further examples are likely to be found in future.

2. Some used to say that the Cambrian explosion represented the first appearance of life. We modified that to the present statement of complex animals with minerliased skeletons. Then we had to change it to macro fossils of complex animals, since Precambrian microfossils of complex animals were discovered. And so it goes. Nothing to see here. Move along.

3. One may say this questions the theory of evolution, but tens of thousands would say it is wholly consistent with it. The "sudden appearance" after a Snowball Earth episode is probably not a coincidence.

4. No theory is ever 100% correct. This is science, not religion.

Re: What is life?

PostPosted: May 19th, 2017, 3:45 pm
by hyksos
Alan McDougall » May 13th, 2017, 4:02 am wrote:What is life?

Give your best short definition of what life really is below.

In universities they tell the biology students a kind of non-committal definition of life. That if a thing X reproduces progeny and transmits traits to them by DNA, that thing X is alive. In informal settings you can get it smaller, "If it copies DNA, it is alive". So doogle's answer is really close to what you hear on campus.

I'm not a personal fan of the DNA=life motto. I'm much more excited about the metabolic non-equlibrium theories. But they are still (unfortunately) still fringe science as of today.

I think we have a resident biologist here. (maybe he already posted in this thread). I think he can vouch for these things.

Re: What is life?

PostPosted: May 26th, 2017, 11:59 pm
by mitchellmckain
I would say that...

Life is a dynamic self-organizing process (in a universe with many such processes) which has attained the capacity for adaptation so that it can maintain its own internal organization apart from the environment through a range of environmental changes. This means the system has something like an awareness of environment and self for it is sensitive to changes in them and responds to these changes. As such, life is a is a highly quantitative characteristic for the degree of this adaptation, sensitivity, and responsiveness varies greatly.

I would argue that the attributes growth and reproduction often used in the definition of life are actually particular strategies of maintenance and adaptation rather than definitive of life itself. For I would argue that organisms do not cease to be alive when they cease to grow or reproduce. But once an organism ceases to maintain its own organization apart from the environment then it has indeed entered into the process we call death. In other words, we call something alive because it does things for in own reasons in response to the environment but when this breaks down so that everything is simply a direct effect of changes in the environment then it is no longer alive.

You can say this means there is a layer of complexity involved between the environmental changes and the internal adaptations. But it is not just complexity because there are reasons for them. For example, an organism typically generates heat in response to a drop in environmental temperature in order to keep the chemical process going which are needed for its own organization and maintenance.

Re: What is life?

PostPosted: July 14th, 2017, 9:54 am
by richardsalvo
According to wikipedia Life is s a characteristic distinguishing physical entities having biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate.

Re: What is life?

PostPosted: July 14th, 2017, 9:05 pm
by Sivad
Life is a chemical process that took on a life of its own.

Re: What is life?

PostPosted: July 14th, 2017, 9:19 pm
by Sivad
...life is a verb. It is not a property that one ascribes to structures per se, but rather to the activity of a structure. Once one makes this simple paradigm shift in thinking, many other apparently mysterious aspects of “matter in the living state” become understandable.

Life is a Process, Not a Thing

Re: What is life?

PostPosted: July 14th, 2017, 11:01 pm
by BioWizard
By the way, whoever thinks all life is fickle should look up tardigrades or extremophiles.

Re: What is life?

PostPosted: July 18th, 2017, 11:41 pm
by mitchellmckain
Sivad » July 14th, 2017, 8:05 pm wrote:Life is a chemical process that took on a life of its own.


Perhaps this was meant to be humorous, but taking it seriously... not only is this circular but it is too restrictive. Chemical process is only one medium in which the process of life can occur. Just because it is happening in the media of nuclear reactions, electronic machinery, or internet communications, for example (all suggested in science fiction), does not mean it isn't life. Indeed I would argue that the human mind is an example of life in a different medium (i.e. in the medium of human language concepts and ideas -- meme life rather than gene life).

Sivad » July 14th, 2017, 8:19 pm wrote:
...life is a verb. It is not a property that one ascribes to structures per se, but rather to the activity of a structure. Once one makes this simple paradigm shift in thinking, many other apparently mysterious aspects of “matter in the living state” become understandable.

Life is a Process, Not a Thing

My definition of life (see it earlier on this page) and the above comment on your post is a follow through on this idea. If life is a general type of process rather than a particular example of it happening in particular stuff then it can be extended to the same type of process occurring in different mediums.

Re: What is life?

PostPosted: July 19th, 2017, 9:02 am
by TheVat
That possibility of different substrates is what Hilary Putnam and other philosophers referred to as "multiple realizability." It is central to the philosophic position, popular with many scientists, called functionalism.

https://plato.stanford.edu/entries/functionalism/

The causal relationships between parts of the system are what matter, not the underlying material.

Re: What is life?

PostPosted: July 20th, 2017, 5:27 am
by mitchellmckain
Braininvat » July 19th, 2017, 8:02 am wrote:That possibility of different substrates is what Hilary Putnam and other philosophers referred to as "multiple realizability." It is central to the philosophic position, popular with many scientists, called functionalism.

https://plato.stanford.edu/entries/functionalism/

The causal relationships between parts of the system are what matter, not the underlying material.


Sure, the term can be adapted in such a way, I suppose. Functionalism was originally about mental states and thus saw the possibilities of intelligence or mind in other mediums. I am instead applying it to the process of life and then see menatility as an example of life in a different substrate.