  We have developed a new evolutionary synthesis code, which incorporates the
output from chemical evolution models. We compare results of this new code with
other published codes, and we apply it to the irregular galaxy NGC 1560 using
sophisticated chemical evolution models. The code makes important contributions
in two areas: a) the building of synthetic populations with time-dependent star
formation rates and stellar populations of different metallicities; b) the
extension of the set of stellar tracks from the Geneva group by adding the AGB
phases for $m_i/M_\odot \geq 0.8$ as well as the very low mass stars. Our code
predicts spectra, broad band colors, and Lick indices by using a spectra
library, which cover a more complete grid of stellar parameters. The
application of the code with the chemical models to the galaxy NGC 1560
constrain the star formation age for its stellar population around 10.0 Gy.
