Why doesn’t urine flow back to the ureters?

With vesicoureteral reflux, urine flows backward from the bladder, up the ureter to the kidney. It may happen in one or both ureters. When the "flap valve" doesn't work and lets urine flow backward, bacteria from the bladder can enter the kidney. This may cause a kidney infection that can cause kidney damage.

you can get banned on this website if you post your quizzes here. . . .

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.