  In recent years, increasing attention has been devoted to semi empirical,
data-driven models to tackle some aspects of the complex and still largely
debated topic of galaxy formation and evolution. We here present a new semi
empirical model whose marking feature is simplicity: it relies on solely two
assumptions, one initial condition and two free parameters. Galaxies are
connected to evolving dark matter haloes through abundance matching between
specific halo accretion rate (sHAR) and specific star formation rate (sSFR).
Quenching is treated separately, in a fully empirical way, to marginalize over
quiescent galaxies and test our assumption on the sSFR evolution without
contaminations from passive objects. Our flexible and transparent model is able
to reproduce the observed stellar mass functions up to $z\sim 5$, giving
support to our hypothesis of a monotonic relation between sHAR and sSFR. We
then exploit the model to test a hypothesis on morphological evolution of
galaxies. We attempt to explain the bulge/disk bimodality in terms of the two
halo accretion modes: fast and slow accretion. Specifically, we speculate that
bulge/spheroidal components might form during the early phase of fast halo
growth, while disks form during the later phase of slow accretion. We find
excellent agreement with both the observational bulge and elliptical mass
functions.
