The side chain of has a pKa in the physiological pH range and is therefore often involved in proton transfer during enzymatic catalysis. a. Arg b. Asp c. His d. Glu

His

Explanation:

The side chain of Histidine has a pKa in the physiological pH range and is therefore often involved in proton transfer during enzymatic catalysis. It is a amino acid which is used for the biosynthesis of protein. Histidine was initially thought to be essential only for infants but now it has  been found to be essential for adults too.If we see the histidine structure contains an α-amino acid, a carboxylic acid group, and an imidazole side chain.

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.

answer: decrease

a limiting factor is the one which decrease the abundance, distribution and causes extinction of the population of species in a ecosystem. here, predators including hawks, owls and snakes are the limiting factor for the population of mexican free tailed bat.   although bats are nocturnal animals as they forge for food at night these predators also may remain active during night which can decrease the population of the mexican free-tailed bats. also, these bats eat only one type of insects that are moths. the food can also be a limiting factor as all 400 members are dependent upon same type of food needs that are moths. the decrease in the moth population can cause decrease in population size of the mexican free-tailed bats.

therefore, the scenarios will most likely to decrease the population size of the mexican free-tailed bats.