Bar-driven galaxy evolution and time-scales to feed AGN

Recent progress in the understanding of the role of bars and gravitational instabilities in galaxy disks is reviewed. It has been proposed that bars can produce mass transfer towards the center, and progressively metamorphose late-type galaxies in early-types, along the Hubble sequence. Through this mass transfer, bars are self-destroyed, and can act only during a certain "duty-cycle" in the galaxy life. After sufficient gas infall, another bar-phase can spontaneously occur. This recurrent evolution is strongly dependent on environment. A scenario is proposed, based on N-body simulations time-scales of the bar-life events, to explain the observed bar frequency, gas mass fraction, bulge and possible black hole mass growth, in a typical spiral.