  In this chapter we provide an overview of the science enabled by radio
continuum surveys in the SKA era, focusing on galaxy/galaxy cluster physics and
evolution studies, and other relevant continuum science in the >2020 scientific
framework. We outline a number of 'reference' radio-continuum surveys for SKA1
that can address such topics, and comprehensively discuss the most critical
science requirements that we have identified. We highlight what should be
achieved by SKA1, to guarantee a major leap forwards with respect to the
pre-SKA era, considering the science advances expected in the coming years with
existing and upcoming telescopes (JVLA, LOFAR, eMERLIN, and the three SKA
precursors: MWA, ASKAP and MeerKAT). In this exercise we take in due account
also the other waveband facilities coming online at the same time (e.g. Euclid,
LSST, etc.), which tackle overlapping scientific goals, but in a different
manner. In this respect particular attention has been payed to ensure that the
proposed reference surveys are able to exploit the existing synergies with such
facilities, so as to generate strong involvement from all astronomical
communities, and leave a lasting legacy value. It is clear that a certain
degree of freedom is allowed to some of the observational parameters. We
believe it is very important to best fine-tune such parameters taking into
proper account existing commensalities with SKA1 surveys addressing other
science areas (HI galaxy science, magnetism, cosmology).
