Materials are stored primarily in vacuoles in single-celled organisms because

A vacuole is known as the storage bag for a cell. Vacuoles are ideal for storing substances because they have a membrane which separates it from other parts of the cell. A vacuole can store nutrients as well as the wastes which need to be excreted. The vacuole helps a single-celled organism to acquire a shape.

In single-celled organisms, vacuoles facilitate the entry and exit of water from the cell and hence help the organism in locomotion.

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation

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.