Abstract

In this thesis several aspects that are connected with the unit of selection problem have been addressed. Common to all different issues discussed in this thesis is the concern with the context dependent character of biological phenomena. First, a conceptual analysis of the structure of biological concepts in general has been presented. A new characterization, the representational account of biological concepts has been developed. Within the framework of this account of biological concepts, the notions of biological character and biological function as well as the unit of selection problem have been discussed. A new representation of the unit of selection, the unit of inheritance has been defined. Second, guided by these conceptual considerations quantitative genetic theory has been further developed. New formulations of epistasis and of average effects at different levels of biological organization have been introduced. The context dependent nature of multiple units of inheritance has been studied for the two locus two allele system. It has been found that the unit of inheritance can change in the course of selection and that with epistasis and linkage disequilibrium in regions away from an equilibrium point units of inheritance exist at levels of biological organization more complex than the single gene. Third, the theoretical results guided an experimental study with an E. coli system. In a selection experiment with transformed strains and with controlled variation it was found that the target of selection, the type of variation targeted by selection, is again context dependent