  Observations of quiescent dwarfs and low surface brightness galaxies suggest
that continuous low rate star formation is likely to occur, during the
quiescent phases between bursts, in dwarf galaxies. We thus have used a
spectrophotometric model to reproduce the observed abundances in IZw 18,
assuming only a low constant star formation rate. We conclude that such a
continuous low star formation rate cannot be neglected, especially when
considering the chemical evolution of very metal poor objects.
