The Interplay between SF and AGN Activity, and its role in Galaxy
  Evolution
  It has become apparent that active galactic nuclei (AGN) may have a
significant impact on the growth and evolution of their host galaxies and vice
versa but a detailed understanding of the interplay between these processes
remains elusive. Deep radio surveys provide a powerful, obscuration-independent
tool for measuring both star formation and AGN activity in high-redshift
galaxies. Multiwavelength studies of deep radio fields show a composite
population of star-forming galaxies and AGN, with the former dominating at the
lowest flux densities (S$_{1.4\mathrm{GHz}}<$100~$\mu$Jy). The sensitivity and
resolution of the SKA will allow us to identify, and separately trace, the
total star formation in the bulges of individual high-redshift galaxies, the
related nuclear activity and any star formation occurring on larger scales
within a disc. We will therefore gain a detailed picture of the apparently
simultaneous development of stellar populations and black holes in the redshift
range where both star-formation and AGN activity peak (1$\leq$z$\leq$4). In
this chapter we discuss the role of the SKA in studying the connection between
AGN activity and galaxy evolution, and the most critical technical requirements
for such of studies
