What is life? Sometimes this question raise in our mind. 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? There are peoples who believe that everything is alive. Can we believe that? Let us find out traits of life using mind storming and available information.
It may not be necessary for a being to be intelligent or able to move for being alive. Computers and even smart phones are becoming artificially intelligent; however, we don’t call them alive. Nor do we call any car or robot alive even though they can move all around. 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 or any other non-living thing unable to exhibit. Eating, drinking, sleeping, moving, speaking and listening all are considered as traits of life by Biologist. However, many of such traits can be found in non-living matter or in some machine. In broader perspective, 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 or 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, flowing water, computers, cars and wind do not reproduce so they are not alive. You do not have to think much to realize that rocks are dead.
Let us go to smaller level. 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. Moreover, 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. Therefore, they are at the boundary of living and non-living things.
Let us go to next smaller level to DNA. All living being has DNA. DNA carries instruction of growth and reproduction. Therefore, we can modify our definition of living being as follows will reduce traits of life from two to one.
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 is 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.
We can define DNA as “chemically active replicating biological compound” rather than a living being. 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 is not a living being. Even though I personally like them to qualify definition of life but sadly at this point they are out of living world.