Distributions of the SFR, sSFR, oxygen abundance, and D_n(4000), from upper to lower panels, for SF galaxies in the samples used in this work (similar to Fig. 2). The median values for each subsample of galaxies are indicated by a vertical line, following the respective colour and line style of each distribution. The number of galaxies in each sample, as well as their corresponding median values, standard deviations, mean values and associated errors, are presented in Table 2.