  We use the distributions of spectral indices of a large homogenous sample of
Fermi-detected blazars to re-investigate the relationship between flat spectrum
radio quasars (FSRQs) and subclasses of BL Lac objects (BL Lacs). We compute
the broadband synchrotron and Compton spectral indices from radio-to-X-ray and
X-ray to gamma-ray bands, respectively. Analyses of our data show continuity in
the distributions of the spectral indices from FSRQs to HSP through LSP and ISP
subclasses of BL Lacs. We find from gamma-ray luminosity distribution that the
jetted radio galaxies form the low-luminosity tail of the distribution,
suggestive that the sequence can be extended to the young jetted galaxy
populations. We observe a significant difference in the shape of Compton and
synchrotron spectra: significant anti-correlation (r ~ -0.80) exists between
the broadband Compton and synchrotron spectral indices. Furthermore, the
broadband spectral indices vary significantly with redshift (z) at low redshift
(z less than 0.3) and remain fairly constant at high (z greater than or egual
to 0.3) redshift. The trend of the variations suggests a form of the
evolutionary connection between subclasses of blazars. Thus, while the
selection effect may be significant at low redshift, an evolutionary sequence
can also be important. Our results are not only consistent with a unified
scheme for blazars and their young jetted galaxy counterparts but also suggest
that the broadband spectral sequence of blazars is not a secondary effect of
redshift dependence.
