  We address the question whether the nucleon's antiquark sea can be attributed
entirely to its virtual meson cloud and, in essence, whether there exists a
smooth transition between hadronic and quark-gluon degrees of freedom. We take
into account contributions from $\pi$ and $K$ mesons and compare with the
nucleon's antiquark distributions which serve as a non-perturbative input to
the QCD evolution equations. We elucidate the different behavior in the flavor
singlet and non-singlet channels and study the dependence of our results on the
scale $Q^2$. The meson-nucleon cut-offs that we determine give not only an
indication on the size of the region within which quarks are confined in a
nucleon, but we find that the scale of these form factors is closely related to
the four-momentum transfer, $Q^2$, where gluons are resolved by a high energy
probe, and that large meson loop momenta, $|{\bf k}| \approx 0.8$ GeV,
contribute significantly to the sea quark distributions. While the agreement of
our calculations with data-based parametrizations is satisfactory and scale
independent for the flavor breaking share of the nucleon's antiquark sea, the
flavor singlet component is quite poorly described. This hints the importance
of gluon degrees of freedom.
