The concept of the economy of nature, as deployed by Linnaeus and Darwin, is a clear invocation of structure in theories of the organic world. And changes in what occupies this structural role offer a perspicuous and heretofore unexplored window on the study of biological theory change.
Pence, C., & Swaim, D. G. (2016). The Economy of Nature: Structure in Biology from Linnaeus, to Darwin, to the Modern Synthesis. The History of Science and Scientific Realism, Indianapolis, Indiana, USA. https://hdl.handle.net/2078.5/91616