  In a four dimensional manifold formalism we study the evolutionary behavior
as well as the ultimate fate of the universe, in the course of which the
contribution of dark energy in these phases are investigated. At one stage we
get a situation (a condition) where the dark energy contained dominates other
types of energies available in this universe. In the model universes we obtain
here the dark energy is found to be of $\Lambda$CDM and quintessence
types-which bear testimony to being real universes. In one of the cases where
the equation of state between the fluid pressure and density is of the type of
the van der Waals equation, it is found that our universe may end in dust. And,
also, it is seen that the behavior of the deceleration parameter is almost
compatible with the recent observation.
