  It is a remarkable feature that various properties of galaxies vary according
to their environments. However, only little has been known on the origin of
this variety in galaxies. Using the Sloan Digital Sky Survey (SDSS) data, we
investigate the morphology-density relation to find two characteristic
environment where the morphology-density relation abruptly changes (0.3 and 2
Rvir).The result has significant implication for the underlying physical
mechanism since it suggests that two different mechanisms might be responsible
for the morphology-density relation. In addition, we study the environment of
unusual spiral galaxies with no [OII] or Halpha emission lines (passive
spirals), and find that passive spiral galaxies preferentially live in cluster
infalling regions (1-10 Rvir}). Thus, the origin of passive spiral galaxies is
likely to be cluster related. Based on all of our observational results, we
propose possible fate of cluster infalling galaxies.
