Choose from three types of scientific workers (for example, biologists, chemists, and geographers) that you think could solve the problems associated with this species, and explain how they could apply their knowledge.

The biologist is the person who would be interested in determining the existence of any pattern or characteristics with in a species and relate it to the characteristics possessed earlier by the species.

All these three i.e biologist, chemist and geographer can use their knowledge to find out the reason behind the problem and hence suggest a corrective measure based on their findings/understandings

Explanation:

Biologist - A biologist study about the genetic structure of an organism and study about its DNA and specific traits that are carried from its for fathers to parents and then to itself. Thereby a biologist can construct a evolutionary tree and hence find out about the root cause of any hereditary issue. Also the/she can inspect the organism physically and thus find the reason behind the problem and could suggest corrective measure

Geographer - A geographer can help in finding the relation between the problem persisting in the organism and the environmental factors that are causing it or adversely affecting it thereby enhancing the problem.

Chemist - A chemist has a good understanding of chemicals and medicines and thus he/she can provide probable solution in terms of using effective medicines or chemicals to cure any biological problem

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.