We all use words like 'alive', 'living', 'lively', 'life' without any real thought as to their meaning. We all know what we mean when we talk about a new life, don't we? We mean a new instance of life; a new example of it, as though some new 'life' has entered the universe.
So what is this stuff called life?
Let's see if we can define 'living' as it applies to 'non-living' things:
Living things grow and repair. Well, yes, to an extent. But single-celled organisms don't repair in the sense that a human can grow some new skin to heal a wound, or can grow new bone to repair a fracture. They may be able to repair some damaged membranes but growth is limited to splitting into two smaller versions and then growing to full size to repeat the cycle.
Living things reproduce. Certainly some do but many don't, yet are none-the-less alive. Yes, their body cells may be reproducing as part of growth and repair but reproduction of new individuals is only a function carried out by SOME living individual, which are no less living for not reproducing.
Living things breathe. Depends on what you mean by 'breathe'. Very few organisms actually shift air in and out of lungs like mammals do. If you mean they have a process of respiration - that is, they take in oxygen and use it for metabolic processes and give off carbon dioxide as a waste product, then many 'living' things certainly do that, yet not all. Anaerobic organisms, like many bacteria do not use oxygen; in fact it's toxic to them. But yes, in the very general sense of exchanging chemicals with their surroundings, respiration can be said to be a characteristic of living things.
Living things move. Many do; many don't. A sedentary organism is no less alive for not moving.
Living things metabolise. Yes. All living things have chemical processes going on inside them. These processes essentially overcome the tendency towards disorder. We call disorder 'entropy'. This has a tendency to increase and can only be reduced locally by increasing it elsewhere. An organism is essentially an entropy reduction machine, using an energy source (an increase in entropy) to reduce local entropy (metabolism).
So, we can say that 'life' is entropy reduction at it's very basic level, can't we?
What then of the idea of 'new life'?
Let's look briefly at how a new multicellular individual, like a mammalian baby, get's made:
Special cells called eggs, or ova, are produced by the female from organs called ovaries. Males produce other special cells called sperm cells from organs called testes. Inside the female's body (in a mammal) a sperm cell enters the ova and fertilises it, so a new cell, made from both the male and the female, is produced and a new individual begins to develop from it.
Yet both the ova and the sperm were alive during all stages in this process. No 'new' life was created at all. All that happened was, the existing 'life' continued. In other words, the metabolism continued; the entropy reduction machine continued to overcome the tendency of entropy to increase locally.
There was no new life; only a new entropy reduction machine.
So what is life? Life is the local reduction of entropy using the energy released by an increase in it elsewhere. We call this 'metabolism'. Life is what we call the biochemical reactions inside living things. There is no special ingredient which makes the chemicals inside a living organism different in some way to other chemicals. The chemicals inside living things are obeying the same basic chemical laws as are the rocks in the ground and the gasses in the air.
And when life ceases, the metabolism stops; or rather, when the metabolism stops, life ceases.
And the meaning of life? You tell me; you can make it mean whatever you want it to mean. (Tweet this)