  We present a model to compute baryon and meson transverse momentum
distributions, and their ratios, in relativistic heavy-ion collisions. The
model allows to compute the probability to form colorless bound states of
either two or three quarks as functions of the evolving density during the
collision. The qualitative differences of the baryon to meson ratio for
different collision energies and for different particle species can be
associated to the different density dependent probabilities and to the
combinatorial factors which in turn depend on whether the quarks forming the
bound states are heavy or light. We compare to experimental data and show that
we obtain a good description up to intermediate values of $pt$.
