What job(s) do these parts of a cnidarian have?
1.cnidocytes
2.gastric cavity
3.Ectoderm-outer cell layer of a cnidarian
4.nematocyst
5.inner cell layer of a cnidarian

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.