Describe the similarities and differences in the way humans and insects obtain oxygen.

There are many ways.

Explanation:

Humans have a combined respiratory and circulatory system, whereas insects do not. In humans, the air is brought in through the mouth/nose, through the windpipe, and into the lungs, the oxygen is absorbed into the bloodstream where it can be transported to muscles and organs. However, insects take in air through tiny holes in their thorax and abdomen. These are called spiracles. The oxygen is stored in many dorsal air sacs to be used. Then carbon dioxide is expelled through the spiracles.

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.