  Predator-prey networks originating from different aqueous and terrestrial
environments are compared to assess if the difference in environments of these
networks produce any significant difference in the structure of such
predator-prey networks. Spectral graph theory is used firstly to discriminate
between the structure of such predator-prey networks originating from aqueous
and terrestrial environments and secondly to establish that the difference
observed in the structure of networks originating from these two environments
are precisely due to the way edges are oriented in these networks and are not a
property of random networks.We use random projections in $\mathbb{R^2}$ and
$\mathbb{R^3}$ of weighted spectral distribution (WSD) of the networks
belonging to the two classes viz. aqueous and terrestrial to differentiate
between the structure of these networks. The spectral theory of graph
non-randomness and relative non-randomness is used to establish the deviation
of structure of these networks from having a topology similar to random
networks.We thus establish the absence of a universal structural pattern across
predator-prey networks originating from different environments.
