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The unanswered question – what is life?

Posted in Biology, Mystery, Philosophy, Psychology, Religion, Science on Tuesday, 10 April 2012

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This edited article about life originally appeared in Look and Learn issue number 686 published on 8 March 1975.

Robot, picture, image, illustration

A robot helps to save life by Wilf Hardy

What is life? Most scientists today admit that they do not know the answer to this question, although they know a great deal about the way in which plants, animals and human beings behave.

If a drop of pond water is examined through a microscope, we see things which move around and things which do not move at all. Many of us might assume that the moving things we can see are alive.

For a very long time, the words animate and inanimate were used to distinguish things that were alive from the things that were not. These words come from the Latin verb animare which means “to set into motion” or accelerate. In fact, the word animal has similar origins. Even in the times of the Romans, there was quite a natural association between life and motion.

Yet few of us today would say that things which move must be alive. Things which seem to move of their own accord, like the modern electronic robots which can fly a plane, or the guided missiles which can “home” on to their target, are not alive.

For anything to be alive, it obviously must have other properties beyond the ability to move around.

Living things can reproduce themselves and grow. In fact, reproduction and growth are very closely connected. A living cell divides into two, and then each of the two cells divides again. Without a microscope, we cannot see this process of cell division actually happening, but we can observe the net result. The plant or animal simply gets bigger as more and more new cells are formed in this way.

Yet, things which are accepted as not being alive can grow too. From school science experiments, we have seen how crystals of salt or copper sulphate can be “grown” in a test tube.

Snowflakes can “grow”. Given the proper condition of temperature and humidity in the atmosphere, tiny ice particles will be formed around particles of atmospheric dust. The crystals get gradually larger and larger and form themselves into the intricate shapes and patterns of snowflakes.

Considering the quite mysterious way in which water molecules arrange themselves like this, the whole process is as complex as many living processes studied by biologists. But we do not say that a growing snowflake is alive.

Animals and plants also contain special “robot” mechanisms which biologists call automatic responses. Under the action of light, heat, pressure or some other stimulus, the plant or animal will automatically behave in a certain way.

A plant tends to grow towards the light. In winter, the hairs of an animal’s fur will stand up, making the fur thicker and offering the animal more protection against the cold. If you accidentally brush your hand against a hot stove, a series of automatic muscle and nerve reactions take place and your hand is smartly pulled away.

Many non-living things, however, can also show these automatic responses. The regulator on a gas oven is a good example. Without human attention, it will turn down the gas if the oven gets too hot, and then turn the gas up again as the oven begins to cool.

Another important property of all living things is their ability to change energy from one form to another. Any living cell is, in fact, like a power station in miniature. Sugar and other substances necessary for life are absorbed into the cell through microscopically small spaces between the molecules which make up the cell wall or membrane.

Depending upon the kind of cell being considered, the chemical energy of sugar can be changed into electrical energy in the case of a nerve cell or mechanical energy which can contract a muscle cell.

The retina of the eye contains special cells which can change light energy into the electrical energy of nerve impulses, carrying the coded information about what we are seeing to the brain.

Many non-living things can make these energy transfers. A motor car can change the chemical energy of petrol into mechanical energy. A camera turns light energy into chemical energy to make a picture. A thermometer changes heat energy into hydraulic energy to make a thin column of mercury rise up in a fine glass tube.

There is, however, another property which we have not discussed – the ability which so many living creatures have of being able to think. Perhaps the answer to our question lies here. But what exactly do we mean by thinking? How does the primitive brain of a grasshopper or the highly developed intelligence of human beings differ from the electronic computers?

Why is it that nervous systems and brains seem confined to the animal kingdom rather than the vegetable kingdom? Or do plants also think, as some people seem to believe?

Some of these questions have not been answered and it may be that life has some deep mysteries which man, for all his intelligence, may never solve.

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