  We present new fully self-consistent models of the formation and evolution of
isolated dwarf galaxies. We have used the publicly available N-body/SPH code
HYDRA, to which we have added a set of star formation criteria, and
prescriptions for chemical enrichment (taking into account contributions from
both SNIa and SNII), supernova feedback, and gas cooling. The models follow the
evolution of an initially homogeneous gas cloud collapsing in a pre-existing
dark-matter halo. These simplified initial conditions are supported by the
merger trees of isolated dwarf galaxies extracted from the milli-Millennium
Simulation.
  The star-formation histories of the model galaxies exhibit burst-like
behaviour. These bursts are a consequence of the blow-out and subsequent
in-fall of gas. The amount of gas that leaves the galaxy for good is found to
be small, in absolute numbers, ranging between 3x10^7 Msol and 6x10^7 Msol .
For the least massive models, however, this is over 80 per cent of their
initial gas mass. The local fluctuations in gas density are strong enough to
trigger star-bursts in the massive models, or to inhibit anything more than
small residual star formation for the less massive models. Between these
star-bursts there can be time intervals of several Gyrs.
  We have compared model predictions with available data for the relations
between luminosity and surface brightness profile, half-light radius, central
velocity dispersion, broad band colour (B-V) and metallicity, as well as the
location relative to the fundamental plane. The properties of the model dwarf
galaxies agree quite well with those of observed dwarf galaxies.
