The stellar mass of star forming galaxies is thought to increase in a quasi-steady state, where the rate depends on the gas fraction and star formation efficiency, which evolve with redshift. Galaxy mergers can lead to more rapid growth while active galactic nuclei have been argued to play an important role in halting star formation. These processes are tied together through the multiphase interstellar medium. I will discuss a program exploring so-called "dense gas" tracers, the use of dust emission as a probe of total molecular gas mass, and the behavior of starbursts in merging dwarf galaxies. This use of multiwavelength tracers and hydrodynamic simulations probes galaxy evolution along axes of nuclear activity, redshift, gas fraction, and metallicity. From these studies I will show new results on identification of heavily obscured AGN and intriguing differences in how mergers trigger starbursts in high gas fraction systems.