3 months ago


There is a constant flow

There is a constant flow of energy and materials into, through and out of the cells. Nevertheless, the cells persist as a whole, despite the continual turnover of materials which compose them. At successive times, the cells may look the same and they may contain the same numbers and kinds of molecules and atoms. But the individual components are not the same ones; some have moved out or have broken down, and others have moved in or have been newly formed. Components at all levels, atoms, molecules, cells and organisms are appearing and disappearing, but continuity of properties is conserved nevertheless. Like a candle-flame or a waterfall, living substance endures despite the continuous replacement of components. Furthermore, killing an organism in order to make it fit our inadequate analytical methods is like putting out a candle-flame in order to study the process of burning. If the matter of the body is continually changing, we cannot expect to be able to describe the characteristics of life in terms of the properties of particular substances. However, specification of chemical units ranging in organisation from organs to pure chemicals is our only means of studying the systems of living things. As yet, we have no means of studying the enormous complicated network of activities that constitutes a single life and we can only attempt to do this by bringing together information collected by various specialists: the morphologists, geneticists, embryologists, physiologists, biophysicists and biochemists. Put another way, when making any observations, whether by dissection, with a microscope, a test-tube, an oscilloscope or respirometer, it is necessary continually to think back to the time when the tissue was active in some living body and to frame the observation so that it shall reveal something significant of that activity. This means that every worker in the biological sciences should know as much as possible of the life Or the whole organism with which he deals and must certainly be aware of the nature of the population from which the specimen was taken. This latter point is often ignored by many biologists, particularly those working with molecules. It is true that each living thing is defined by its own chemical pattern, but the specific pattern of life is not necessarily to be found in any one individual, still less in the parts of an individual. The unit of life is that which tends to be preserved through time and is, 28

therefore, the whole interbreeding population, and it is in his dealings with populations that the biologist is distinguished from other scientists. To summarise, the way to study wallflowers, rats or men is first and foremost, to examine them whole, to see how their actions serve to meet the requirements of the environment and so allow the preservation of the life of the individual and race. Then, with this knowledge of how the animal 'uses' its parts, we are able to make more detailed studies down to the molecular level and show how, together, the activities form a single scheme of action. Action is the characteristic feature of living, compared with lifeless, matter. To most people, animals are generally more lively than plants. Even when asleep, an animal is breathing, its heart is beating and brain pulsing. The waking life, of course, shows this restless action even more clearly. It is at this level of 'animals-alive' that we see the side of biology that is most interesting to the bulk of humanity. However, to make sense of animals alone or in groups is very difficult and it is no accident that it is more often found that the easier path is taken and we spend our time examining the structure and chemistry of the dead. Animals versus plants Following the line of defining zoology, there remains the problem as to the fundamental difference between plants and animals. Why do we call this organism a plant and this an animal? Most people would not hesitate, but would say that the animal moved, whereas the plant did not; that the animal was conscious, while the plant was not; that the animal devoured its food while the plant absorbed its nutriment from its surroundings. None of these criteria, however, are absolute. Many animals, like corals or sea squirts are as rooted to the spot as most plants, while some undoubted plants move about. With regard to consciousness, no-one could assert with confidence that a sponge, an undoubted animal, possessed a higher level of consciousness than a mushroom or a wallflower. On the point of nutrition, many animal parasites absorb 29

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