  Evolutionary synthesis models for Tidal Dwarf Galaxies (TDGs) are presented
that allow to have varying proportions of young stars formed in the
merger-induced starburst and of stars from the merging spirals' disks. The
specific metallicities as well as the gaseous emission of actively star forming
TDGs are consistently accounted for. Comparison of models with observational
data (e.g. Duc, this volume) gives information on the present evolutionary
state and possible future luminosity evolution of TDGs. The redshift evolution
of merger rates and of the gas content and metallicities of spiral galaxies are
used to estimate the number of TDGs at various redshifts and to investigate
their contribution to magnitude limited surveys.
