Many time it happens that we are debating whether something is living or nonliving. Is a rock alive? How about flowing water or gushing wind? Why we can’t say machines are alive when they can work and move around? How about trees? So what are the traits we saw in something to call it alive? Let us find out using mind storming.
It is not necessary for a being to be intelligent or able to move for being alive. Computers and even smart phones are becoming artificially intelligent but we don’t call them alive. Nor do we call any car or robot alive even though they can move all around. You don’t have to think hard before you said that of course rocks are dead. They are not alive. What is it that a living being can do but a rock or a car or a robot can’t do? There must be some unique traits of living being which machines and matter does not exhibit. Eating, drinking, sleeping, moving, speaking and listening all can be done by some machine or matter. For me the two most important traits of living being are as follows:
- Ability of reproduction
- Ability to grow and accumulate things needed for survival in at least one medium like air, water, ice and soil etc.
Without any doubt animals including human are alive and fulfill both conditions. Plants too are alive as they too grow and reproduce. Machines, rocks, flowing water, computers, cars and wind do not reproduce so they are not alive.
Cells are alive. Unicellular organisms are also alive. Virus is a tough choice. Virus are special in that they behave as living when they are inside the body of another organism. But when they are out-of-body they became dead. Both traits of life are not found in them when they are outside of body of another organism. So they are at the boundary of living and non-living things.
Let’s go to next smaller level to DNA. All living being has DNA. DNA carries instruction of growth and reproduction. So we can modify our definition of living being to this. Anything that has a DNA is alive.
Does DNA itself is alive is a big question. Since we cannot define word by word itself, we have to go back to our primary traits of life. If DNA can reproduce and if it can grow by itself than DNA is alive else, it’s a nonliving code of chemical compound which makes every other thing alive when suitably fitted with DNA. DNA does not full fill second condition of life i.e. growth.
DNA can be considered as “chemically active replicating biological compound” rather than a living thing. As a computer chip can store information and give instruction for motion to machine but we do not call it alive. In same way DNA can’t be considered as living. Even though I personally like them to qualify definition of life but sadly at this point they are out of living world.
Let’s go to next smaller Level-Atom and molecules. Atoms has electrons which keep moving around nucleus. They also do a lot of fuzzy things and every living being is made up of atoms. But Atoms are not living by themselves. They neither can grow nor can reproduce. So every living being is made up of nonliving matter. This is an incredible conclusion.
To be continued if readers like to read further…