If grass stores 2,000 energy units received from the sun, the ecological efficiency of the ecosystems is 10% and the trophic levels are grass – cow – human, how many units of energy does the human receive of the original 2000 units?

20 units of energy

Explanation:

Given that the ecological efficiency of the ecosystem is 10%, (meaning as energy is transferred from one trophic level to another, 90% of energy is being lost), units of energy the human received of the original 2000 units can be calculated as follows:

Energy received by grass = 2000 units

Energy transferred to cow = 10% of 2000 units = 10/100 × 2000 units = 200 units (1800 units is lost)

Energy transferred from cow to the human = 10% of 200 units = 10/100 × 200 = 20 units (180 units lost)

Only 20 units of the original 2000 units is received by the human.

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.