This conversation is closed.

Life, but not as we know it. Does this statement make sense?

How do we define life? The diversity of life on Earth is so vast and mind-boggling it would be difficult to pin life down to colour, shape, or size.

We can only define life by the biologist definition which says life is anything that performs the 7 life processes which are movement, nutrition, respiration, irritability, excretion, growth and reproduction.

If an object was found outside the Earth that met the criteria for life it would definitely be classified as life. If another object was found that resembled life on Earth (though difficult to say how life on Earth looks like ) but did not meet the criteria would it be classified as life or would the definition of life be bent to include it.

If so why is a similar situation not considered for celestial bodies that meet the definition partially. And also for man-made objects such as cars which are 80% a life form. After-all there is no part of the definition that narrows it to natural objects only.


  • thumb
    Jul 26 2013: No single definition of life is universally accepted, but that's not considered a problem. We don't actually need a definition, except that we feel more comfortable having one. Virus is an example of a form that some biologists accept as a life form while others do not. They don't metabolize, except in reproduction within a host cell. But you might say the same of many parasites that spend years in a non-metabolic spore form, before finding a host.

    Our definition of life is strictly empirical - we've made a definition to describe that which we've already decided to call "life". So when we find a new form, we'll first decide if we want to call it life, and if so we'll adjust the definition to fit the new "being". No problem.
  • thumb
    Jun 27 2013: Hi,

    This statement definitely makes sense if you give it some sense. I don't feel like discussing definitions right now and would like to ask the following question - how can this debate make our lives better? What are you looking for?

    The very first thing that came to me after seeing the topic was the notion of the thinking, intelligent ocean that I read about many years ago, isn't that What do we know of life?

    Best wishes.

    PS. Don't get confused by this or my profile, the above are just some thoughts.
  • thumb
    Jun 27 2013: Good topic for a debate, of course. Some of the modern robots can perform that 7 processes (including grow and reproduction) doing it in their way, just as anyone can watch in some TED talks. Then, could we find a new process or characteristic feature por life's definition? It would be very interesting.
  • thumb
    Jun 26 2013: While was in university , I read somewhere there are some viruses those show none of the characteristics of being something with life when it is outside host body , but once these get a host displays numbers of characteristic being living. As I read , those viruses are considered being bridge between living and non living world.
  • Jun 26 2013: Maybe.

    I'm not a biologist, but if I was in a space mission far away from earth and I needed to decide if something was a life form or not, I would take only 2 things into account: 1) Is this thing actively seeking or collecting energy and material resources (needs food)?. 2) Is this thing processing its food somehow in order to extract energy and keep it self in good shape (has a metabolism)?. If the answer to both questions would be "yes" then I would classify it as a living thing.

    So using this criteria your car is 0% of a life form, since it is not actively seeking for gasoline and it doesn't metabolize gasoline in order to keep its wheels healthy, however something like Wall-E (did you see the movie?) would be classified as a living thing since it actively sought energy in the form of sun light and food in the form of spare parts which then used to fix itself, an extremely simple, mechanical and mostly external "metabolic" process if you will, but in the end it had the same result as a biochemical metabolic process... please correct me if I'm wrong.
    • Jun 27 2013: modern cars do actively seek fuel, GPS's locate nearby fuel stations when fuel is low and the car may or may not drive there.
      • Jun 27 2013: True, but unless they drove all by them selves to the nearest gas station, and got the fuel all by themselves with absolutely zero human aid, I think to say they actively seek fuel is a little bit too daring statement. So your car is still dead, sorry for the bad news.
  • thumb
    Jun 26 2013: Definitions can be problematical. If you insist that life as we know it is strictly as defined by the 7-point system then anything which does not comply is not life, by definition. Therefore the answer to your question is, "No. The statement makes no sense." Anyone who has been kicked by a mule will testify that the kick came from a living creature, yet the mule fails to meet the definition because all male mules are sterile. If you allow a different definition which includes life forms not yet discovered, then the statement would make sense.
    • Jun 27 2013: Life is defined for a specie not an individual or group of individuals. If all the members of a human tribe are sterile it does not make reproduction no longer a life process. And even for multi-icellular organisms we look at it from a cellular point of view, the cells of a mule perform all the 7 life processes, yes, its cell reproduce.
      • thumb
        Jun 27 2013: The last of the seven processes you mention as signs of life is "reproduction". Are you asserting that the process in view there is cellular reproduction within a member of a species and not the ability to generate offspring? Please clarify that rather startling assertion. Thank you!