  The main purpose of this study is to investigate aspects regarding the
validity of the AGN unification paradigm (UP). In particular we focus on the
AGN host galaxies, which according to the UP should show no systematic
differences depending on the AGN classification. For the purpose of this study
we use (a) the spectroscopic SDSS (Sloan Digital Sky Survey) DR14 catalogue, in
order to select and classify AGNs using emission line diagnostics, up to a
redshift of z=0.2, and (b) the Galaxy Zoo Project catalogue, which classifies
SDSS galaxies in two broad Hubble types, spirals and ellipticals. We find that
the fraction of type-1 Seyfert nuclei (Sy1) hosted in elliptical galaxies is
significantly larger than the corresponding fraction of any other AGN type,
while there is a gradient of increasing Spiral-hosts from Sy1 to Liner, type-2
Seyferts (Sy2) and Composite nuclei. These findings cannot be interpreted
within the standard Unification Paradigm, but possibly by a co-evolution scheme
for supermassive black holes (SMBH) and galactic bulges. Furthermore, for the
case of spiral host galaxies we find the Sy1 population to be strongly skewed
towards face-on configurations, while the corresponding Sy2 population range in
all host-galaxy orientation configurations, having a similar, but not
identical, orientation distribution with star-forming galaxies (SF). These
results also cannot be interpreted by the standard Unification Paradigm, but
point towards a significant contribution of the galactic disk to the
obscuration of the nuclear region. This is also consistent with the observed
preference of Sy1 nuclei to be hosted by ellipticals, ie., the dusty disk of
spiral hosts contributes to the obscuration of the broad line region (BLR) and
thus relatively more ellipticals are expected to appear hosting Sy1 nuclei.
