  The structure and dynamics of dark matter halos, as predicted by the
hierarchical clustering scenario, are at odds with the properties inferred from
the observations at galactic scales. My Thesis addresses this problem by taking
an evolutionary approach. I analysed in detail the many and different
observational evidences of a discrepancy the predicted halo equilibrium state
and the one inferred from the measurable properties of disk galaxies, as well
as of the scaling relations existing between the angular momentum, geometry and
mass distribution of the luminous and dark components, and realized that they
all seem to point towards the same conclusion: the baryons hosted inside the
halo, by collapsing and assembling to form the galaxy, perturb the halo
equilibrium structure and made it evolve into new configurations. From the
theoretical point of view, the behaviour of dark matter halos as collisionless
systems of particles makes their equilibrium structure and mass distribution
extremely sensitive to perturbations of their inner dynamics. The galaxy
formation occurring inside the halos is a tremendous event, and the dynamical
coupling between the baryons and the dark matter during the protogalaxy
collapse represents a perturbation of the halo dynamical structure large enough
to trigger a halo evolution, according to the relative mass and angular
momentum of the two components. My conclusion is that the structure and
dynamics of dark matter halos, as well as the origin of the connection between
the halo and galaxy properties, are to be understood in in terms of a joint
evolution of the baryonic and dark components, originating at the epoch of the
collapse and formation of the galaxy.
