I wish to discuss two basic questions:
1) what do we know from the observations about the relationships between the physical conditions of the Interstellar medium (ISM) in disk galaxies and their past and present star formation rate, heating of dust and acceleration of relativistic cosmic rays ?
2) are the above relations and mechanisms sensitive to the intergalactic environment in rich clusters of galaxies?
I will discuss these questions by reviewing three topics:
a) gas content versus star formation
b) FIR emission versus star formation
c) radio continuum emission versus star formation and by discussing weather and how these topics are related to the environment.