Dwarf and Low Surface Brightness Galaxies

I review the evolutionary status of the field populations of starbursting dwarf galaxies and low surface brightness spirals. Particular attention is paid to the long standing problem of the progenitors for star burst galaxies, which may be related to a population of small, low surface brightness dwarfs. Larger low surface brightness spirals are known to evolve slowly, converting little of their gas mass into stars and metals in a Hubble time. Their slow evolution is controlled by their low densities, which arise naturally from formation by late collapse of low amplitude perturbations in the initial density field.