How does smoking make an individual more susceptible to infections?

The active smokers and those getting exposed, that is, passive smokers are at enhanced threat of bacterial infections. Getting exposed to tobacco smoke enhances vulnerability to respiratory tract infections, comprising pneumonia, tuberculosis, and Legionnaires disease.  

Smoking compromises the anti-bacterial activities of leukocytes incorporating monocytes, neutrophils, B cells, and T cells, thus, demonstrating the mechanism for enhanced risk of infections.  

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.