I don't understand how to answer this question:
Discuss the environment and habitat of a dog and of a flea that lives on it

Parasitism: The parasite (flea) lives off and harms the host (the dog)

Explanation:

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.