What is this life, if…?

“Somewhere, something incredible is waiting to be known.”

–          Carl Sagan

The very first concept a child learns in science is usually the distinction between living and nonliving things. Seven characteristics that define life are movement, nutrition, growth, respiration, excretion, reproduction, and response to stimuli (as stated in several school textbooks). As a biology teacher, this is first concept that I am expected to teach. As a biologist, this is one concept I am yet to understand!

If we go by this set of necessary features that characterize an entity as living, then what about those who cannot reproduce. Let alone the sterile plants that grow in my garden, what about those human beings who are biologically unable to give birth to a little one? Are they not living? And what about those lying in a coma who have lost most abilities to respond to external stimuli? Are they nonliving?

Maybe I understood it wrong; perhaps it is that not all these characteristics are essential to define an entity as living. It is just that these are the characteristics that are unique to living beings and the presence of one or more of them in an entity mark it as living. However, if that is the case, then the old Honda Dio in my house that drinks fuel like crazy (nutrition), utilizes that fuel for energy (respiration), uses the energy to move (movement), and coughs up exhaust fumes like a forest set afire (excretion) is a fully competent living being! Computer viruses that can replicate, stars in our ever expanding universe that grow, and the new AC with “intelligent sensors” that Katrina endorses these days, all appear to share characteristics of a “living being”.

So then what is “LIFE”?  The more I read the more I have begun to realize that the concept of life is one that baffles both philosophers and scientists. At which point did the first organism supposedly evolve from inanimate matter? What is it truly that distinguishes us from nonliving things? If we discover a colloidal mass of molecules on mars (let’s say) that trap solar energy and convert it into another form of energy, would we say we have discovered life?

Many scientists have come up with varied theories and definitions each trying in their own way to identify a distinct basic property to define life. Current theories identify cellular nature, heredity and evolution as some of the components that define life.  Physicists too, are trying to make sense of the complex system using their understanding of the physical world. Theories of emergent behavior and self-assembly are some of the many examples. But as someone who dabbles in molecular biology, again all these theories only indicate chemistry. When did this chemistry evolve into “bio”? Honestly, I am not desperate for an answer at the moment.

I just wish I knew how I could, in all justice, make a third grader understand- what defines life?


– Savitha Sekhar

Associate Specialist


5 thoughts on “What is this life, if…?

  1. Dear Savitha,

    You are right. I understand the dichotomy between teaching as it is in the text books and what you yourself understand about a subject. My personal belief is that we human beings develop in a manner in which some things make sense at young age and some others when we grow up. Keeping this in mind, we are now left with a task to teach a complex phenomenon in the simplest way to young children. There could be more than one approaches to this task. My personal pick would be to make things as simple as possible and design and come up with unique ways to make children grapple with these phenomenon. You did a very good job by raising this issue. You should be proud of yourself.



  2. Thank you sir,
    To an extent, I understand the molecular mechanisms that make living beings unique. But as I mentioned, It is quite difficult to keep that understanding at the back of my head and stand before a class to help them understand the “living things” chapter as described in their textbooks in it’s correct sense.



  3. Dear Miss. Savitha,

    Nice writeup and fun reading. The thing is that, the difference between living and non living is pretty much clear. There is no such thing like a doubt over it. It is like revisiting the idea of earth being flat or round. We can always argue against, by giving examples like the ones present in your writeup. There is always a literal description and a detailed description. In case a school child points out that his father’s motorbike is living because it drinks fuel and moves faster than most living organisms, then he is right in literal sense. The child will be in no position to grasp the point that living organisms have hierarchical message flow like DNA-RNA-Protein and his father’s bike has none of these molecules. The best way to deal with this situation is to teach children the virtues of patience.

    Your writeup is very nice and well written. Thanks for sharing.

    Best wishes



    1. Very nice writeup, raises deep and eternal questions.

      A couple of points I had regarding the reply above:

      “The thing is that, the difference between living and non living is pretty much clear. There is no such thing like a doubt over it. “

      But isn’t science itself observer dependent? The only way we can know about our surroundings is through the senses and whatever information
      we observe/record/interpret & deduce (even using mathematical ideas) becomes observer dependent. So, having said that, does objective reality exist at all?
      As the famous example goes, a fish inside a fish bowl has a fundamentally different physical view of the universe. Assuming it has the intellect to create concepts and a language (like mathematics) to explain its view, we can’t say that it is wrong or qualitatively any lesser than our theories/explanation of the universe.
      So, the distinction between the living and non-living that we have drawn up and ‘generally’ accepted(and works exceedingly well with our other theories) is based on our own observations but we have no way to prove (in scientific terms) that it is real and without a doubt.

      “living organisms have hierarchical message flow like DNA-RNA-Protein and his father’s bike has none of these molecules”

      Again, these are based on general observations. For that matter taking even the ‘detailed description’, we are explaining the chemical which is based on physics, which in turn on mathematics and the whole of mathematics rests on axiomatic set theory. Without an observer, is there a distinction from one set and another? Doesn’t it just collapse into a unity which just exists? (I don’t know the answer too, of course 🙂 )



      1. Dear Raghavendra,
        Welcome to our blog! Thanks for your thoughtful and insightful comment.
        The point of the article is to trigger questions and lead to the possibility of finding answers. Thanks for your enthusiastic participation in the discussion.


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