The evolutionary tracks of 12+log(O/H) vs. gas fraction (upper panel) and Y − (O/H) relation (lower panel) as predicted by our best models (M_inf = 10⁹ M_⊙) with metal-enhanced wind (w_H,He = 0.3). The solid red, dash-dotted black, long-dashed magenta and short-dashed blue lines are the results of M9b1, M9b2, M9b3 and M9b4 in Table 3. The observational data are same as in Figs. 2 and 4, open cyan circles for BCDs and open cyan triangles for dIrrs.