  Dwarf galaxies (DGs) serve as extremely challenging objects in extragalactic
astrophysics. Their origin is expected to be set as the first units in CDM
cosmology. Nevertheless they are the galaxy type most sensitive to
environmental in uences and their division into multiple types with various
properties have invoked the picture of their variant morphological
transformations. Detailed observations reveal characteristics which allow to
deduce the evolutionary paths and to witness how the environment has affected
the evolution. Here we refer to general morphological DG types and review some
general processes, most of which deplete gas-rich irregular DGs. Moreover, the
variety of pecularities is brie y refered, but cannot be comprehensively
analyzed because of limited paper space.
