Oxygen and carbon dioxide diffuse in and out of a leaf through the:
a)taproot
b)stomata
c)phloem
d)guard cell

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.

trachea, alveoli, lung capillaries, arteries