  Due to their low gravitational energies, dwarf galaxies are greatly exposed
to energetical influences from internal and external sources. By means of
chemodynamical models we show that their star formation is inherently
self-regulated, that peculiar abundance ratios can only be achieved assuming
different star-formation episodes and that evaporation of interstellar clouds
embedded in a hot phase can lead to a fast mixing of the interstellar gas.
Metal-enriched hot outflows can accrete onto infalling clouds by means of
condensation leading to a large range of timescales for the self-enrichment of
the ISM from local scales within a few tens of Myr up to a few Gyr for the
large-range circulation. Infall of clouds is also required to explain abundance
ratios of metal-poor galaxies at evolved stages because it reduces the
metallicity altering only marginally the abundance ratios.
