  We discuss the detection of redshifted line and continuum emission at radio
wavelengths using a Square Kilometer Array (SKA), specifically from
low-excitation rotational molecular line transitions of CO and HCN (molecular
lines), the recombination radiation from atomic transitions in almost-ionized
hydrogen (radio recombination lines; RRLs), OH and water maser lines, as well
as from synchrotron and free-free continuum radiation and HI 21-cm line
radiation. The detection of radio lines with the SKA offers the prospect to
determine the redshifts and thus exact luminosities for some of the most
distant and optically faint star-forming galaxies and active galactic nuclei
(AGN), even those galaxies that are either deeply enshrouded in interstellar
dust or shining prior to the end of reionization. Moreover, it provides an
opportunity to study the astrophysical conditions and resolved morphologies of
the most active regions in galaxies during the most active phase of star
formation at redshift z~2. A sufficiently powerful and adaptable SKA correlator
will enable wide-field three-dimensional redshift surveys at chosen specific
high redshifts, and will allow new probes of the evolution of large-scale
structure (LSS) in the distribution of galaxies. The detection of molecular
line radiation favours pushing the operating frequencies of SKA up to at least
26 GHz, and ideally to 40 GHz, while very high redshift maser emissions
requires access to about 100 MHz. To search for LSS the widest possible
instantaneous field of view would be advantageous.
