  We show that a global relation between baryonic mass and virial velocity can
be constructed from the scale of dwarf galaxies up to that of rich galaxy
clusters. The slope of this relation is close to that expected if dark matter
halos form in the standard hierarchical cosmogony and capture a universal
baryon fraction, once the details of halo structure and the adiabatic
contraction of halos due to cooling gas are taken into account. The scatter and
deficiency of baryons within low mass halos ($V_{vir} < 50$ km/s) is consistent
with the expected suppression of gas accretion by photo-evaporation due to the
cosmic UV background at high redshift. The data are not consistent with
significant gas removal from strong supernovae winds unless the velocities of
galaxies measured from their gas kinematics are significantly lower than the
true halo velocities for objects with $V_{vir} < 100$ km/s. Thus models such as
$\Lambda$CDM with a steep mass function of halos may find it difficult to
reproduce both the baryonic mass-velocity relation presented here whilst at the
same time reproducing the flat luminosity/HI function of galaxies. Galaxies
hold about 10% of the baryons in the Universe, which is close to the collapsed
mass fraction expected within hierarchical models on these scales, suggesting a
high efficiency for galaxy formation. Most of the baryons are expected to be
evenly distributed between diffuse intergalactic gas in low density
environments and the intra-galactic medium within galaxy groups.
