Size and Cycle: An Essay on the Structure of Biology

Abstract

For some years I have been concerned about the problem of the rela tion of genetics, evolutio , and evelopment. It has always seemed that their conventional relation is to some extent static and contrived, while in fact they must be closely integrated and part of one scheme. A problem with so many interrelated facets can be looked at a number of different ways, and here one will be chosen which it is hoped will help to reveal some of the fundamental relations. The method holds no dispute with any of the basic tenets of modern biology; this is not an attack on either the facts or the theories of biology today. Rather it is a regrouping of those facts and theories in such a fashion that new and deeper insights may possibly be achieved. Part of our present difficulty is that so many of our ways of looking at biology have slowly grown out of the past that we are infiltrated and imprisoned by a massive tangle of traditions and conventions. What we teach today is part biology and part history. There is nothing wrong with this but we do not always know where one begins and the other ends. The view taken here is that the life cycle is the central unit in biology. The notion of the organism is used in this sense, rather than that of an individual at a moment in time, such as the adult at maturity. Evolution then becomes the alteration of life cycles through time; genetics the inheritance mechanisms between cycles, and development all the changes in structure that take place during one life cycle. When looked at this way the size of the organism in the cycle takes on a particular significance. Size is correlated with time, for in general large organisms have long cycles and furthermore the different parts of the cycle can be readily classified on the basis of their size characteristics. The life cycle is a summation of all the molecular or biochemical steps, one following another in a well-ordered sequence. The difference between two cycles is a difference in the nature of the steps. They differ in their structure, their composition, and therefore the life cycle is a qualitative unit. A change in size of the organism, on the other hand, does not necessarily require that there be a qualitative difference in the steps, but merely more steps. Therefore the life cycle is quality, and size is quan tity. One is a statement of composition of matter and the changes in that composition; the other is merely a statement of quantity. Just as in

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