Number density of galaxies for the SDSS DR7 in the mass-age and mass-metallicity planes, obtained using both the volume and completeness statistical corrections. Following the same colour-code of Fig. 3, we give the distributions obtained without aperture corrections (left panels) and the distributions obtained from aperture-corrected indices (right panels). The red arrows (left panels) represent the median shift of galaxies in each bin due to the implementation of aperture corrections. The dotted horizontal lines indicate the solar metallicity of Z_⊙ ≡ 0.02.