The organism-environment relationship plays a central role in how different theories and scientific practices of the life sciences are structured and conducted. However, understanding how this relationship has been construed remains an open problem that has not been sufficiently examined by historians and philosophers of science. In this project, I seek to explore what kind of relationship is instantiated when ‘organism’ and ‘environment’ are considered relata. If both are said to stand in a relation of reciprocity, what is entailed by this claim? Is this relationship wholly symmetrical or are there some particular characteristics of these relata which break the symmetry of the pairing? I assess different understandings of organism-environment reciprocity in contemporary and historical debates across the life sciences: in particular, I focus on ontological co-constitution, mutual structural fitting, concomitant reaction, and reciprocal causation. In addition, I peruse what separates an organism from its environment (if anything) and what constitutes the foundational asymmetries of this relationship. I contend that only the former relatum (i.e., an organism), though deeply embedded and causally affected by its surroundings throughout its ontogeny, is a self-individuating entity and a bounded locus of causation (i.e., an agent) which performs goal-directed actions and exhibits intrinsic normativity.