Redshift evolution of the gas-phase He/H−O/H abundance pattern in our three simulated disc galaxies. The blue points correspond to the predicted gas-phase abundances at redshift z = 0, orange points to z = 0.5, green points to z = 1, and red points to z = 2. The black and grey triangles with error bars correspond to the observational data of Aver et al. (2015) for a sample of metal-poor HII regions within 16 emission-line galaxies in the Local Universe; the black triangles correspond to their qualifying sample, whereas the grey triangles mark the abundances affected by large systematic uncertainty. Finally, the magenta points with error bars correspond to the observational data of Fernández et al. (2019).