  A model for the parton distributions in hadrons is derived from simple
physical arguments leading to an analytical expression for the valence
distributions. The sea parton distributions arise mainly from pions in hadronic
fluctuations. Evolving from a low Q^2_0 scale with DGLAP gives the proton
structure function F_2(x,Q^2) in good agreement with DIS data. An extension of
the model to describe intrinsic charm quarks in the proton is discussed.
