  We present a phenomenological model for understanding the origins and
evolution of galaxy morphologies from a phenomenological perspective. The model
includes an observationally motivated prescription for star formation in galaxy
disks, as well as a merger-driven starburst mode of star formation. We consider
the formation of bulges and ellipticals both in mergers and by global
instabilities in disks. We use our model to investigate the fundamental
properties of disk galaxies and the effects of surface-brightness limits on
large galaxy surveys.
