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ABSTRACT

Homeostasis is an abiding principle of living systems; it is defined as that "relatively stable state of equilibrium or tendency toward such a state between the different but interdependent elements and subsystems of an organism" (Webster); accordingly, metrical trait values (e.g., blood pressure and plasma glucose concentration) are maintained within limits. Whereas Claude Bernard had only observed constancy of the "milieu interieur" (extracellular fluid), homeostasis actually extends to intracellular and subcellular environments and components. Because of biological individuality, each individual will have a particular location within the larger distribution of quantitative values that describe the parameter in the population; the private homeostatic value may then be seen to be displaced because the individual’s system is undermined (by mutation perhaps) or overwhelmed by experience. A displaced value is likely to be disadaptive because evolution of biological diversity by natural selection was the process by which the optimal range of homeostatic values was obtained.

HOMEOSTASIS: A LEGACY OF BIOLOGICAL EVOLUTION

Homeostasis is an abiding principle of living systems; it is defined as that "relatively stable state of equilibrium or tendency toward such a state between the different but interdependent elements and subsystems of an organism" (Webster); accordingly, metrical trait values (e.g., blood pressure and plasma glucose concentration) are maintained within limits. Whereas Claude Bernard had only observed constancy of the "milieu interieur" (extracellular fluid), homeostasis actually extends to intracellular and subcellular environments and components. Because of biological individuality, each individual will have a particular location within the larger distribution of quantitative values that describe the parameter in the population; the private homeostatic value may then be seen to be displaced because the individual’s system is undermined (by mutation perhaps) or overwhelmed by experience. A displaced value is likely to be disadaptive because evolution of biological diversity by natural selection was the process by which the optimal range of homeostatic values was obtained.

WHY MUTATIONS ARE LIKELY TO BE "RECESSIVE"

The genomic nucleotide sequence may be a book of life but it is also "an intricate community" with "intergenic wildernesses" and "social collectives where genes play intricate divisions of labor and functional collaborations" (Avise,1). Accordingly, the genome signifies complexity in the background against which Mendelian mutant phenotypes act out their roles.

Fisher, when arguing that mutation is essential for biological evolution, proposed that the "successful" allele should become the wildtype, meaning it would become dominant. [See Scriver22 for citation of Fisher and Sewall Wright, and for additional discussion.] Hence, by invoking evolution through natural selection, Fisher thought he could explain dominance of the wildtype allele. Wright, a contemporary of Fisher, in recognition of the prevalence of recessive mutant alleles, approached the problem from a different point of view--for example, in metabolism. The network or chain of events linking genotype to phenotype would involve fluxes of molecules in the fluid state of living systems. If several ...

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