What is pericardium?By which muscular tissue does the heart form?

Pericardium is a thin sac that surrounds our heart. And Cardiac muscles tissue is muscles tissue that form heart.

Explanation:

Pericardium protect and lubricates our heart and keep it in place within our chest.

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.