Which process make meiotic cells genetically different and occurs during prophase 1, but not durning prophase 2

Crossing over is the event that occurs during prophase 1 but not during prophase 2.

During crossing over genetic material is exchanged between the non-sister chromatids of homologous chromosomes.

The two homologous chromosomes pair with each other and lie in close proximity during synapsis.

Then the genetic material is exchanged at the points of chiasmata.

It results in the formation of new combinations of alleles which forms the basis for the genetic variation in a population.

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.