Growth and development rates are fundamental to all living organisms. In a warming world, it is important to determine how these rates will respond to increasing temperatures. It is often assumed that the thermal responses of physiological rates are coupled to metabolic rate and thus have the same temperature dependence. However, the existence of the "temperature-size rule" (TSR) suggests intraspecific growth and development are decoupled. Decoupling of these rates would have important consequences for individual species and ecosystems, yet this has not been tested systematically across a range of species. We conducted an analysis on growth and development rate data compiled from the literature for a well-studied group, marine pelagic copepods, and use an information theoretic approach to test which equations best describe these rates. Growth and development rates were best characterised by models with significantly different parameters: development has stronger temperature dependence than growth across all life stages. As such it is incorrect to assume these rates have the same temperature dependence. We used the best fit models for these rates to predict changes in organism mass to temperature. These predictions follow a concave relationship, which complicates attempts to model the impacts of increasing global temperatures on species body size.