Models of evolution of gas and abundances in dwarf irregular galaxies
  We have developed a grid of chemical evolution models applied to dwarf
isolated galaxies, using \cite{gav05} yields. The input data enclose different
star formation efficiencies, galaxy mass and collapse time values. The result
is a wide collection of solutions that vary from objects with low metallicity
and great amount of gas, to those with little gas and high metallicity. No
environmental effects like tidal or galactic winds have been treated, so these
objects are expected to be close to field dwarf galaxies, more than cluster
ones. We have studied the time evolution of the abundance of oxygen and
nitrogen and the amount of gas, related to their star formation history, as
well as the possibility of gas losses by SN winds.
