  The influence of the initial composition of the exploding white dwarf on the
nucleosynthesis, light curves and spectra of Type Ia supernovae has been
studied in order to evaluate the size of evolutionary effects on cosmological
time scales, how the effects can be recognized and how one may be able to
correct for them.
  The calculations are based on a set of delayed detonation models which give a
good account of the optical and infrared light curves and of the spectral
evolution. The explosions and light curves are calculated using a one-
dimensional Lagrangian radiation-hydro code including a nuclear network. NLTE-
spectra are computed for various epochs using the structure resulting from the
light curve code.
  The following questions are addressed : What do we learn about the progenitor
evolution and its metallicity? What are the systematic effects for the
determination of the cosmological parameters $\Omega_M$ and $\Lambda$ and how
can we recognize this potential 'pitfalls' and correct for evolutionary
effects?
