The brain ventricle located in the diencephalon is the ventricle.

Explanation:

Brain Ventricles:

Ventricle system consists of "2 lateral ventricles", "the third ventricle", "the cerebral aqueduct", and the "fourth ventricle".

diencephalon:

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.