1. We have added a Gift Upgrades feature that allows you to gift an account upgrade to another member, just in time for the holiday season. You can see the gift option when going to the Account Upgrades screen, or on any user profile screen.
    Dismiss Notice

Define life

Discussion in 'Off-Topic' started by insurgent, Aug 25, 2004.

  1. Bozo Erectus

    Bozo Erectus Master Baker

    Joined:
    Jan 22, 2003
    Messages:
    22,389
    On the basic level: anything that uses things found in its environment to produce copies of itself.
     
  2. hawai_74

    hawai_74 mac über alles

    Joined:
    Aug 5, 2003
    Messages:
    1,074
    Location:
    switzerland
    life is from the moment i wake up til i go to bed
     
  3. Marla_Singer

    Marla_Singer United in diversity

    Joined:
    Oct 24, 2001
    Messages:
    12,988
    Location:
    Paris, west side (92).
    I like that one. :)
     
  4. Aphex_Twin

    Aphex_Twin Evergreen

    Joined:
    Sep 7, 2002
    Messages:
    7,474
    A shot at it.

    The criteria in this order:

    1. Stimulus response
    2. Metabolism (ability to process things from the environment)
    3. Homeostasis
    4. Reproduction

    I define life as something that posesses at least the first 3 characteristics and is the offspring of something with all characteristics or can produce offspring with at least the first 3.
     
  5. Mise

    Mise isle of lucy

    Joined:
    Apr 13, 2004
    Messages:
    28,622
    Location:
    London, UK
    "Reproduce" as in "cell reproduction" rather than species propagation.

    But yes, I agree that it isn't a proper definition.

    Excrete as in release waste products from the system.

    Sorry it seems I should have elaborated. ("system" means organism in question)
    - Feed: ingest chemicals into the system
    - Breathe: take in oxygen and give out carbon dioxide
    - Respire: convert chemicals they feed on to release energy
    - Excrete: release waste products from the system
    - Grow: increase in size
    - Reproduce: multiply on a cellular level, or on the system level (i.e. make babies)
    - Respond: ~ to external stimuli
    - Move: umm... move.

    Homeostatis? How do plants do that? I thought this was a characteristic of animals, rather than life in general. Plants exchange gas at different rates depending on the light level, and overproduce CO2 or O2 as a result. That would indicate that they don't care much for keeping their levels of various chemicals constant.
     
  6. Phasmida

    Phasmida Chieftain

    Joined:
    Aug 24, 2004
    Messages:
    77
    Location:
    In a house
    Mise's definition seems pretty good to me... what living thing doesn't exhibit those traits?
     
  7. Aphex_Twin

    Aphex_Twin Evergreen

    Joined:
    Sep 7, 2002
    Messages:
    7,474
    For instance... An individual worker ant/termite/bee doesn't reproduce. Plants don't move. Not all beings grow throught their life. Certain butterflies never feed after they emerged from the cocoon.
     
  8. Marla_Singer

    Marla_Singer United in diversity

    Joined:
    Oct 24, 2001
    Messages:
    12,988
    Location:
    Paris, west side (92).
    So what. You're gettin examples of specialization... and in the case of butterflies, it's not because it doesn't want to feed anymore that it hasn't feed itself before to grow.... so it's rather pointless.

    But anyway, I like a lot the definition from DP. I like especially its simplicity. :)
     
  9. Mise

    Mise isle of lucy

    Joined:
    Apr 13, 2004
    Messages:
    28,622
    Location:
    London, UK
    Ant's etc. are made up of living cells which reproduce. Also, it could be argued that the *species* is capable of reproduction, therefore members of the species are living.

    Plants move! Their flowers open, their leaves fold at night, etc.

    What beings don't grow throughout their lives?

    Those butterflies still feed though, whilst in their cocoons. Humans feed, even though they dont do so for most of the day.
     
  10. Bozo Erectus

    Bozo Erectus Master Baker

    Joined:
    Jan 22, 2003
    Messages:
    22,389
    I think it says it all. Who would deny that something which takes energy from its environment and uses it to copy itself is alive? Nobody serious I think.
     
  11. Mise

    Mise isle of lucy

    Joined:
    Apr 13, 2004
    Messages:
    28,622
    Location:
    London, UK
    Fire does that too :p

    Damn fire! It spoils every theory!

    But it's one thing to say, "all living things do this," but quite another to say "no non-living things do this which living things do." Man that was a confusing sentence!
     
  12. betazed

    betazed Seeking...

    Joined:
    May 9, 2003
    Messages:
    5,224
    Not so fast. By that definition, thunderstorms would be alive. They take energy from the environment and make little thunderstorms. And What about waves in the ocean?

    Edit: x-post with Mise.
     
  13. Gastric ReFlux

    Gastric ReFlux Dispatch our Tech Staff

    Joined:
    Jun 25, 2002
    Messages:
    717
    I've seen this idea talked about here. It may well be correct to state that non-life to life exists along a spectrum and there is no real clear dividing line between the two ends.
     
  14. Aphex_Twin

    Aphex_Twin Evergreen

    Joined:
    Sep 7, 2002
    Messages:
    7,474
    What if we only know of a single member (a worker and) of an ant species. The species itself has no chance to reproduce (through usual means). Do we consider that ant living?


    Then we can only argue those living cells are alive and not the ant itself. The definition for a species requires a DNA. If we meet something on an alien planet which exhibits certain characteristics (stimumus-response, homeostasis,...) and we don't find a structure symilar to DNA can we conclude we have found life?

    Again what I said to Marla. If we have found a single butterfly that does not feed and that can't be catalogued in any known species, can we conclude it is life?

    Plants don't "move about", but I'll agree if you originally meant this.

    I'm trying to find a set of necessary and sufficient criteria for life. Meaning, given those and only those we can say for sure we have found life and not life in the general sense (species), but individual. In other words, what tests can we put a small/large lump of "something" to qualify as life.
     
  15. Bozo Erectus

    Bozo Erectus Master Baker

    Joined:
    Jan 22, 2003
    Messages:
    22,389
    Hmm.., Fascinating... I must think now.
     
  16. betazed

    betazed Seeking...

    Joined:
    May 9, 2003
    Messages:
    5,224
    Best of luck, sincerely. :) When you do find it do not forget to send it to NASA. They need it too.

    Btw, that is a key question in Astrobiology. I mean, how can we test for something if we cannot even define it properly? :crazyeye:
     
  17. Aphex_Twin

    Aphex_Twin Evergreen

    Joined:
    Sep 7, 2002
    Messages:
    7,474
    I can try, can't I? :)

    Give a shot at my criteria, and don't be afraid to tear them appart (as I know you will). ;)
     
  18. Marla_Singer

    Marla_Singer United in diversity

    Joined:
    Oct 24, 2001
    Messages:
    12,988
    Location:
    Paris, west side (92).
    No, that's neither true in the case of thunderstorms nor in the case of waves since in both cases they are reproducing smaller entities of themselves... Not copies of themselves. That makes a huge difference.

    Moreover, I should add that in our instinctive way to apprehend what life is. The fact it's an autonomous being is extremely important. A plant grows in a specific way to reach sunlights. Neither storms nor waves do such a thing. They aren't looking for energy, they don't specifically go where there are energy. They have absolutely no freedom of movement. Just like the example of the Earth.

    When you want to get counter-example, you're forced to distort it. ;)


    Edit : Actually, in the case of storms, waves or fire... those phenomenons are simply energy. Life isn't energy, Life uses the energy in its environment to reproduce copy of itself.
     
  19. Gastric ReFlux

    Gastric ReFlux Dispatch our Tech Staff

    Joined:
    Jun 25, 2002
    Messages:
    717
    Well, fire releases energy, but in its most familiar form, it is atoms of carbon combining with atoms of oxygen to produce that energy. Fire is not simply energy, it has a rather physical presence that quickly disperses in the process.

    The point that the threadstarter may have wished to raise here is that life is an emergent property of basic physical processes, that life becomes more so as it evolves more complexity.

    That idea has been much more aptly expressed in the link I provided above.
     
  20. Marla_Singer

    Marla_Singer United in diversity

    Joined:
    Oct 24, 2001
    Messages:
    12,988
    Location:
    Paris, west side (92).
    So what. :undecide:
    How does that prove my point is wrong ? ;)
     

Share This Page