  Context. Tidal dissipation in planets and in stars is one of the key physical
mechanisms that drive the evolution of planetary systems.
  Aims. Tidal dissipation properties are intrisically linked to the internal
structure and the rheology of studied celestial bodies. The resulting
dependence of the dissipation upon the tidal frequency is strongly different in
the cases of solids and fluids.
  Methods. We compute the tidal evolution of a two-body coplanar system, using
the tidal quality factor's frequency-dependencies appropriate to rocks and to
convective fluids.
  Results. The ensuing orbital dynamics comes out smooth or strongly erratic,
dependent on how the tidal dissipation depends upon frequency.
  Conclusions. We demonstrate the strong impact of the internal structure and
of the rheology of the central body on the orbital evolution of the tidal
perturber. A smooth frequency-dependence of the tidal dissipation renders a
smooth orbital evolution while a peaked dissipation can furnish erratic orbital
behaviour.
