  Variations in the photometric parameters of stellar systems as a function of
their evolution and the stellar populations comprising them are investigated. A
set of seven evolutionary models with an exponential decrease in the
star-formation rate and 672 models with a secondary burst of star formation are
considered. The occurrence of a secondary burst of star formation can shift the
position of a stellar system on two-color diagrams to the right or left of the
normal color sequence for galaxies and the extinction line. This makes it
possible to estimate the composition of the stellar population of a galaxy with
a nonmonotonic star formation history from its position on two-color diagrams.
Surface photometry in both the optical (UBVRI) and near-IR (JHK) is used to
study the stellar populations and star-formation histories in the structural
components (nucleus, bulge, disk, spiral arms, bar, ring) of 26 galaxies of
various morphological types (from S0 to Sd). Components (nucleus, bulge, bar)
with color characteristics corresponding to stellar systems with secondary
bursts of star formation are indicated in 10 of the 26 galaxies. The parameters
of these secondary bursts are estimated. Five of the 10 galaxies with complex
star-formation histories display clear structural perturbations. Appreciable
differences in the photometric characteristics of relatively red early-type
galaxies (S0-Sb) and relatively blue later-type galaxies (Sb-Sd) have been
found. Galaxies of both early and late types are encountered among the
Sb-galaxies. Lenticular galaxies do not display different photometric
characteristics from early-type spiral galaxies.
