We present the analysis of a sample of Hα, Hβ, and [O II] emission line galaxies from the OTELO survey, with masses typically below $\mathrm{log}({M}_{* }/{M}_{\odot })\sim 9.4$ and redshifts between z ~ 0.4 and 1.43. We study the star formation rate, star formation rate density, and their number density and evolution with redshift. We obtain a robust estimate of the specific star formation rate-stellar mass relation based on the lowest-mass sample published so far. We also determine a flat trend of the star formation rate density (SFRD) and number density with redshift. Our results suggest a scenario of no evolution of the number density of galaxies, regardless of their masses, up to redshift z ~ 1.4. This implies a gradual change of the relative importance of the star-forming processes, from high-mass galaxies to low-mass galaxies, with decreasing redshift. We also find little or no variation of the SFRD in the redshift range of 0.4 < z < 1.43.