There has long been a deep fault zone in the basic theoretical paradigm of biology: the fault zone between functional biology and evolutionary biology. Ernst Mayr once discussed this issue. He pointed out that for thousands of years biological phenomenon has been divided into two categories: physiology (functional biology) and natural history (evolutionary biology). The difference between them is that the former studies the recent causations (organism and its components' functions and developmental program, ranging from functional morphology to biochemistry), while the latter studies the ultimate cause (the causes for adaptation, the evolution of a given genetic program, and natural selection). These two biological theories each involve different causation and are separated from each other.
Mayr suggested that all biological processes have both recent and ultimate cause. Only if a biological problem's recent cause and ultimate cause have been clarified can the problem be satisfactorily resolved. Study of evolution causation and study of physical-chemical causation are parts of biology. However, there is an enormous theoretical and methodological fault zone between them. Biophysics, biochemistry, and physiology have an emphasis on law, prediction, quantification, and measurement, as well as functions of biotic process, while natural history, evolutionary biology, and ecology have a focus on character, species, comparative study, ecological niche, and selective value, as well as biotic adaptation and value. Therefore, biology needs a new synthesis which should be able to build a new unity associating the function-organ-regulation conceptual system with the species-ecology-adaptation conceptual system.
Experimental developments of intraspecific comparative study may provide a new connection to close the fault zone between evolutionary and functional biology. This is an important breakthrough: intraspecific comparison might be able to give adaptive variation an explanation at the physiological level. This is reflected in the following new understandings:
1) Intraspecific ecological optimality in phenotypic physiology can be interpreted as: organism uses its phenotypic physio-morphs of genotype to form efficiency advantages in response to habitat changes.
2) Variant patterns of functional operation can be interpreted as: organismal component's behavior in different phenotypic physio-morphs is restricted by different modulations.
Therefore, the physiology of biotic adaptation can be expressed as: a systemic self-modulation bestows different restrictions on the components' behavior to build different phenotypic advantages in response to different niche conditions.
Therefore, a new understanding of adaptation that is based on a combination fusing physiology with ecology comes into being. This is a reductionistic analysis of biotic adaptation, a new approach to structure analysis. In other words, intraspecific comparison has demonstrated that the biotic adaptation is physiologically structural and can be reduced and analyzed. This is another important contribution made by intraspecific comparison to the theoretical development of biology. Intraspecific comparative study establishes a new coupling over the fault zone between functional biology and evolutionary biology, opening a gate for the reductionistic analysis of evolutionary biology at the physiological level.
This new reductive method is based on a new view and comprehension of the structure of life: in a given physioecological phenotypic physio-morph, any one component of being may take a specific part and contribute to a dominant systemic resistance to the environmental stress. That is to say, a given set of components constitute a physiological phenotypic physio-morph which may have specific ecological efficiency advantage. These components are specifically subject to some limitations and restrictions in the process of joining to form the physio-morphs. Therefore, adaptive variation may be reduced to a combined relation of phenotypic physio-morph units among the concrete components, upon which a structural relation among different phenotypic physio-morph units can be formed. Thus, intraspecific comparison may change biotic adaptation into a new kind of structural analysis problem. That is the deep structure study which is very different from the functional structure research in traditional biology.