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Author Topic:   Is there a border dividing life from non-life?
dokukaeru
Member (Idle past 2144 days)
Posts: 129
From: ohio
Joined: 06-27-2008


Message 121 of 132 (481784)
09-12-2008 2:38 PM
Reply to: Message 115 by AlphaOmegakid
09-12-2008 10:03 AM


Re: Resurrection of topic due to interest
AOKid writes:

A regious zealot who ignores scientific evidence about life and pursues mythological stories about the origin of life coming from the evolutionary emergence of chemicals.


This is your own made up definition. You cannot reference one, correct?

AOKid writes:

Yes, and I think the last time I checked 100% of scientists in the world would still predict that those who have been brought "back to life" will still die eventually.

That is not the point. The point is they have crossed the boundry you say cannot be crossed.

AOKid writes:

Except for the one who has power (that's a physics term) over life and death (those are biological terms)....Jesus Christ who rose from the dead and lives today. I put the parenthetical statements in because this is a science forum.

You do realize the ressurection myth was around well before Christians commandeered it?

wiki writes:

Centuries before the time of Jesus Christ the nations annually celebrated the death and resurrection of Osiris, Tammuz, Attis, Mithra, and other gods" [1]. A cyclic dying-and-rising god motif was prevalent throughout ancient Mesopotamian and classical literature and practice (eg in Syrian and Greek worship of Adonis; Egyptian worship of Osiris; the Babylonian story of Tammuz; rural religious belief in the Corn King).

Specifically, some of language concerning resurrection in the Hebrew Bible appears to have origins in Canaanite belief as demonstrated by the Baal cycle found at Ugarit in Northern Syria. Ba'al-Hadad's battle against Mot seems to be the origin of the some of the resurrection imagery found in Hosea, Isaiah and Daniel. This influence survives into the New Testament and even Rabbinic literature, with agricultural imagery regarding resurrection in 1 Corinthians 15:36-37 and in John 12:24 reflecting the agricultural images of the Ba'al myth. [1]


This message is a reply to:
 Message 115 by AlphaOmegakid, posted 09-12-2008 10:03 AM AlphaOmegakid has not yet responded

    
Dr Adequate
Member
Posts: 15950
Joined: 07-20-2006
Member Rating: 4.6


Message 122 of 132 (481788)
09-12-2008 3:00 PM
Reply to: Message 104 by AlphaOmegakid
08-25-2008 4:15 PM


Re: Resurrection of topic due to interest
There is a distinct border between chemicals and living organisms.

I still can't figure out whether you're pushing vitalism or not.

There is no border, because living organisms are made of chemicals.


This message is a reply to:
 Message 104 by AlphaOmegakid, posted 08-25-2008 4:15 PM AlphaOmegakid has not yet responded

  
Rahvin
Member (Idle past 716 days)
Posts: 3964
Joined: 07-01-2005


Message 123 of 132 (481795)
09-12-2008 4:10 PM


In any question over the dividing line between life and non-life, we first need to discuss what life is. Arbitrary assertions of "that's alive" and "that's not" are uselessly subjective and carry a discussion nowhere. We need a set of properties that all life posesses so that we can identify any specimen as "alive" or "not alive" by a comparison to those criteria only, and not subjective preconceived conclusions. This is the way that all of taxonomy works, by classifying organisms according to their properties.

So what defines life?

1) All life reproduces, though the manner of reproduction varies significantly (sexual, mitosis, etc).

2) All life metabolizes energy from its environment, though the method again varies significantly (photosynthesis, consumption of organic matter, etc).

3) All life responds to stimuli (though all forms of life do not respond to all stimuli).

That's about it. We know that all life we've ever seen is organic (carbon-based), but we don't know whether that's the only possibility, so there's no reason to include that in the definition. We know that all examples of life we have ever seen came from pre-existing forms of life, but we know that it's possible for life to arise from non-living matter (whether spontaneously or directly created by an intelligence), despite the fact that the manner in which this occurs is still unknown, so saying that all life comes from pre-existing life is needlessly exclusive - if we find a specimen that meets all of the other deifinitions of life but which was not spawned from a pre-existing life-form, defining the specimen as "not alive" would be arbitrary and subjective.

Let's take a look at some examples of living things. We all know that these things are alive, so there should be no controversy.

1) Human beings. Obviously, we're an example of life. We reproduce, we metabolize energy from our surroundings, and we respond to a great deal of stimuli.

2) An oak tree. Trees reproduce, though the method is compeltely different from human reproduction. They metabolize energy, though again it's in a completely different manner from ours. They respond to stimuli, though very differently and over longer timescales than we do - trees grow towards light, for example.

Let's look at a few things that are not alive.

1) A desk. Though it can be made of once-living matter, desks cannot reproduce, they do not metabolize energy, and they do not respond to stimuli.

2) A rock. Again, rocks respond to no stimuli, do not reproduce, and do not metabolize. They are inert.

Suppose somewhere (deep in the ocean, or maybe on Io, it doesn't mater) we find something intresting - a complex crystalline object that grows towards heat sources, and uses that heat energy combined with the surrounding matter to grow. After enough growth, peices of the crystal will break off due to its size, and the peices will continue to grow, metabolize the heat, and respond to the presence and absence of heat.

Is this object alive?

By the earlier definitions, yes it is. It responds to stimuli (heat), reproduces (by a version of budding), and metabolizes energy from its environment.

But lets say we find a specimen that's a bit less clear-cut. This next example reproduces, but needs a host organism in order to do so. It metabolizes energy only within the host. It responds to stimuli only by the presence or absence of its host, and irrevocably ceases metabolization and reproduction if removed from the host.

This would loosely meet the conditions we set earlier. But what did I just describe?

Did I describe an immobile parasite with a life-cycle compeltely dependant on host organisms to feed and reproduce? Many parasites are compeltely dependant on their hosts for metabolizing energy (many "hijacking" the host's own digestive system so that the parasite can simply absorb the already-digested nutrients) as well as reproduction (there are species of parasitic wasps for example that reproduce only in the bodies of spiders paralyzed by their sting), and respond to stimuli only by being "active" in their adapted environment.

Or did I describe a virus like HIV? Viruses require host cells to reproduce and metabolize energy ("hijacking" the machinery and even DNA of the cell to perform both functions), and again only respond to stimuli in becoming active inside of a proper host cell. When outside of a human body, the virus quickly "dies" due to an inhospitable environment, irrevocably losing the ability to function even with a host cell.

Most people would identify a parasite as "alive." Yet for viruses, their status as "living" or "nonliving" is debateable. Many people insist that viruses are not alive becasue they are not composed of cells, but that's an arbitrary classification - why must all life be cellular even if it meets all of the other conditions for being defined as alive? AOKid claims that viruses are not alive outside of a host cell, but why, if they can still become active when placed in the environment of a host cell where they can function? A better definition of "dead" in this case would be that the virus can no longer become active, as is the case of HIV when out of the body. At the very least this claim is an admission that viruses are "alive" inside of a host cell, meaning they are still an interesting example of something that doesn't fall neatly into the "alive"/"not alive" categories. In a bit of irony, you could say that in this instance AOKid is even admitting that the nonliving matter of a virus becomes alive in a cell, and nonliving matter becoming alive spontaneously is the very definition of abiogenesis.

What about prions? Even simpler than viruses, prions are complex proteins that essencially turn other proteins into additional prions. They're responsible for such things as "Mad Cow Disease," and basically contradict everything we knew about reproduction. They definitely reproduce, but they don't really metabolize and can't really be said to respond to stimuli any more than a bicycle - if the structure is broken, neither continue to function.

What about sperm? They don't directly reproduce, they're a means for reproduction - sperm do not beget additional sperm. Yet they metabolize energy and respond to stimuli, but they don't metabolize from their surroundings, they don't have "food" or derive energy from photosynthesis. They can be said to "die" due to temperature or Ph differences, becoming inert. Most people would count sperm as "alive."

It would seem that the question of "living" vs "nonliving" is not the binary yes/no, black/white classification it is commonly assumed to be. Many things in the world meet some of those conditions, but not all of them. I wouldn't say that prions are alive, certainly, but I would say they are more alive than an inert rock. I would say that viruses are more alive than prions, but less than bacteria or plants or animals. It would seem we have a spectrum at the simple levels of life, a gradual progression from completely inert matter to simple chemical compounds that meet some of the conditions of life and leading eventually to truly living things.

Discussions regarding abiogenesis are useless without defining what life is. Subjectively claiming "viruses are not alive" or "sperm is alive" are nothing more than bare assertions without the qualification of the properties that define life. And when we come up with such properties, so long as we maintain objectivity and do not arbitrarily restrict our definition to extant forms of life, we inevitably find that the line between life and death is blurry.


Replies to this message:
 Message 124 by New Cat's Eye, posted 09-12-2008 4:47 PM Rahvin has responded
 Message 126 by cavediver, posted 09-13-2008 8:25 AM Rahvin has not yet responded

  
New Cat's Eye
Member
Posts: 11704
From: near St. Louis
Joined: 01-27-2005
Member Rating: 2.3


Message 124 of 132 (481798)
09-12-2008 4:47 PM
Reply to: Message 123 by Rahvin
09-12-2008 4:10 PM


So what defines life?

1) All life reproduces, though the manner of reproduction varies significantly (sexual, mitosis, etc).

2) All life metabolizes energy from its environment, though the method again varies significantly (photosynthesis, consumption of organic matter, etc).

3) All life responds to stimuli (though all forms of life do not respond to all stimuli).

That's about it.

You didn't mention homeostasis.

From a lecture outline from Biology 111 chapter 2 from an accredited university:

quote:
2.1 What Does Life Require?
A definition of life:
There is no simple definition of life
• How can scientists determine if something is living and what characteristics do all living things possess?

A Definition of Life
• Some characteristics of living organisms are shared with some non-living things, like fire:
– Growth (develop and metamorphose)
– Metabolism (chemical processes that occur in the cell)
– Movement
– Reproduction
– Response to external environmental stimuli

A Definition of Life
• All living organisms…
– contain a common set of biological molecules
– can maintain homeostasis (a roughly constant internal environment)


bold added for emphasis

Edited by Catholic Scientist, : No reason given.


This message is a reply to:
 Message 123 by Rahvin, posted 09-12-2008 4:10 PM Rahvin has responded

Replies to this message:
 Message 125 by Rahvin, posted 09-12-2008 5:38 PM New Cat's Eye has not yet responded

  
Rahvin
Member (Idle past 716 days)
Posts: 3964
Joined: 07-01-2005


Message 125 of 132 (481804)
09-12-2008 5:38 PM
Reply to: Message 124 by New Cat's Eye
09-12-2008 4:47 PM


My intention was not to provide an exhaustive set of properties shared by all life, but rather to show that, once those properties are defined, it is inevitable that there will be examples that partially satisfy those properties and occupy a "gray area" of sorts. In some cases there will be "organisms" that fully satisfy the condiions of being defined as "alive," but not as clearly so as other examples.

The properties of what defines a living thing are always going to be somewhat arbitrary and are of necessity based only on the examples of life we see here on Earth. It's always possible that we'll find something that, while technically not meeting the conditions we've defined, is undeniably "alive." For example, I remember a textbook that included a precondition that all living things are carbon-based, and of course we have AOKid's assertion from another thread that all life is cellular. While those are the case here on Earth so far, if we observed a silicon-based entity that met every other condition of being defined as "alive," it would be difficult to justify the arbitrary inclusion of the "must be carbon-based" condition. This is a significant issue in the search for extraterrestrial life - there's no guarantee that life we find away from Earth will be even remotely similar to life we observe here. Knowing that life works one way doesn't mean life cannot work in a different way.

I think it's pretty obvious that the statement you bolded, that "there is no simple definition of life," is completely accurate, and saying as much was basically the entire point of my post.


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cavediver
Member (Idle past 1173 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 126 of 132 (481873)
09-13-2008 8:25 AM
Reply to: Message 123 by Rahvin
09-12-2008 4:10 PM


Thanks Rahvin, great post. I've never been able to dissuade myself completely of the notion that stars are 'alive' to some limited extent, given their entire life-cycle taken over successive generations. As for AOKid - anyone who continues to suggest that somehow the LoB has anything to do with abiogenesis, does not have sufficent mental capacity to engage in rational discussion. He should be ignored until he's reached his twenties and gained some maturity in his thinking.
This message is a reply to:
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AlphaOmegakid
Member (Idle past 405 days)
Posts: 564
From: The city of God
Joined: 06-25-2008


Message 127 of 132 (482109)
09-14-2008 6:20 PM
Reply to: Message 119 by dokukaeru
09-12-2008 2:20 PM


Re: Resurrection of topic due to interest
doku writes:

This is not true. Blood cells have an average life of 4 months. You are saying that when one of my blood cells dies, I die.


More fallacies doku. This is a total strawman argument. Yes bood cells die all the time. Blood cells are organisms. And like all organisms, they die. I guess you don't know the difference between a multicellular organism and a single celled organism.

doku writes:

Science has had problems trying to define death because new technologies have extended life past previous definitions. New definitions rely on the cessation of brain activity and function. What is to stop science from keeping a brain alive indefinitely?

Death....................and God for that matter.

Biological science has problems definining alot of things. That's why they can fool people like you.

doku writes:

The analogy still holds. The machine's functions stop. The cell's functions stop.

The analogy doesn't have a leg unless you agree with itelligent design. With no intelligence, no design changes, and no ability to fix the failing machine. The medical field is wonderful evidence of intelligent design. But even the most intelligent human designer cannot prevent death indefinitetly.

doku writes:

Actually yes I do. there is scienctific evidence for it. Here are 2 examples:

1. The hydra is a radially symetrical organism ranging in size from 1mm-20mm. Hydras do not age. They are biologically immortal.

I think your fallacies are immortal doku. Now you equivocate aging with dying. All hydras die. They just don't age.

doku writes:

2. Did you know that some cultivars of grapes are clones that have existed for thousands of years? Did you know every Granny Smith apple comes from a single chance plant that was grown in 1868 in Austailia by Maria Ann Smith? You cannot grow a Granny Smith or any other variety of apple from seed. Wouldn't you agree that is immortality?

Nope. Fallacy after fallacy! I guess tulips and potatos are immortal too? They aren't grown from seeds either. Maybe we shouldn't be so hard on Mickey D's for frying all those immortal taters. Who knows, It seems to me that life expectancy started increasing about the time McDonalds came into the world. Maybe the potatto is the tree of life! :laugh::laugh:

doku writes:

The telomeres do not have to be infinitely long, just infinitely extended.

This one takes the cake doku. I guess every 40 years or so we will have microscopic surgeries to have telomere extensions for all of our 6 trillion cells. Yes, He has the faith!

And you guys think creos are religious?


This message is a reply to:
 Message 119 by dokukaeru, posted 09-12-2008 2:20 PM dokukaeru has responded

Replies to this message:
 Message 128 by AdminNosy, posted 09-14-2008 7:08 PM AlphaOmegakid has not yet responded
 Message 129 by dokukaeru, posted 10-24-2008 11:21 AM AlphaOmegakid has not yet responded
 Message 131 by DevilsAdvocate, posted 11-19-2008 11:49 AM AlphaOmegakid has not yet responded

  
AdminNosy
Administrator
Posts: 4753
From: Vancouver, BC, Canada
Joined: 11-11-2003


Message 128 of 132 (482117)
09-14-2008 7:08 PM
Reply to: Message 127 by AlphaOmegakid
09-14-2008 6:20 PM


AoK 24 hours
You are suspended AoK for a day. This will give you time to discuss in a semi adult manner. When you are prepared to actual answer the posts in the discussion and behave with some more maturity then you can continue.
This message is a reply to:
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dokukaeru
Member (Idle past 2144 days)
Posts: 129
From: ohio
Joined: 06-27-2008


Message 129 of 132 (486762)
10-24-2008 11:21 AM
Reply to: Message 127 by AlphaOmegakid
09-14-2008 6:20 PM


Curious if you have any more input
Have you thought any more about Message 119 or Message 120 or anyones post after those?
This message is a reply to:
 Message 127 by AlphaOmegakid, posted 09-14-2008 6:20 PM AlphaOmegakid has not yet responded

    
Fosdick 
Suspended Member (Idle past 3029 days)
Posts: 1793
From: Upper Slobovia
Joined: 12-11-2006


Message 130 of 132 (488474)
11-11-2008 7:32 PM
Reply to: Message 1 by sidelined
05-01-2004 11:47 PM


sidlined writes:

I hold that there is no actual border between the two and that it is a matter of bias on the part of we conscious humans.


The border in question may not be a physical or a chemical one. Instead, it may be an informational one. You could go to another planet with all the physical and chemical attributes of Earth, but if there were no genetic information there would be no life. Life didn't start until the genes got here. And that's border in question, IMO.

—FTF


I can see Lower Slobovia from my house.
This message is a reply to:
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DevilsAdvocate
Member (Idle past 631 days)
Posts: 1548
Joined: 06-05-2008


Message 131 of 132 (488913)
11-19-2008 11:49 AM
Reply to: Message 127 by AlphaOmegakid
09-14-2008 6:20 PM


Re: Resurrection of topic due to interest
AlphaOmegakid writes:

More fallacies doku. This is a total strawman argument. Yes bood cells die all the time. Blood cells are organisms. And like all organisms, they die. I guess you don't know the difference between a multicellular organism and a single celled organism.

Blood cells are not living organisms and they are not single celled organisms. They are biological components of a larger organism the that serve specific functions for that organism. Red blood cells have no nucleus and thus no DNA. They cannot reproduce and after they leave the body of their host they begin to decompose (due to their lack of ability to metabolize). That is why cryogenically preserved blood only lasts a couple of months before it has to be discarded. However individual blood cells death does not equate to an organisms death unless it is in large quantities as the result of disease, etc. The bone marrow in our bodies produce new red blood cells at the rate of millions per second and these blood cells live for approximately 4-5 months before decomposing back into the blood stream. In fact, none of the cells in our bodies are more than 10 years old at any point in our lives.

Thus doku is correct to say that cellular death does not necessarily equate to an organisms death.


This message is a reply to:
 Message 127 by AlphaOmegakid, posted 09-14-2008 6:20 PM AlphaOmegakid has not yet responded

  
DevilsAdvocate
Member (Idle past 631 days)
Posts: 1548
Joined: 06-05-2008


Message 132 of 132 (488974)
11-20-2008 1:09 PM
Reply to: Message 130 by Fosdick
11-11-2008 7:32 PM


Fosdick writes:

The border in question may not be a physical or a chemical one. Instead, it may be an informational one. You could go to another planet with all the physical and chemical attributes of Earth, but if there were no genetic information there would be no life. Life didn't start until the genes got here. And that's border in question, IMO.

But then the question become could this genetic information have chemically evolved naturally in the right conditions (i.e. low oxygen levels in early Earth atmosphere, etc) from naturally present organic compounds & molecules found in that environment. Or not. So again the scenario you pose does not elimate the question of what is life and what is not-life. IMHO.


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 Message 130 by Fosdick, posted 11-11-2008 7:32 PM Fosdick has not yet responded

  
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