<p>Paradigmatic examples of laws drawn from physics are accompanied by a rich explanatory structure that supports unificatory efforts. Part of the reason these efforts have been successful has been their identification of conservation laws, whose greater necessity allows them to act as constraints. Within biology, much of the debate over lawhood has focused on whether restricted regularities should be treated as laws, rather than finding parallels to how physical laws are structured. This paper argues that extending that structure to biology is both possible and well-motivated by building on the functionalist approach to lawhood. Through two specific examples – the West Brown Enquist model of metabolism and the neutral theory of biodiversity – I show there are principles in biological theorising that can be interpreted as analogues of conservation laws. This reveals a similarity of nomological structure between physics and biology which is often obscured by methodological differences. Commitment to these laws in biology supports the view that theoretical progress can be made by focusing research efforts on unificatory principles.</p>