In The Call of the Wild, describe Buck's changes.

I think that Buck changes because he learns to fully grasp
the nature of human cruelty.  Buck undergoes changes from a domesticated dog to a wild
one as a result of all that is done to him.  His abduction from Judge Miller was the
result of human deceit and through this, Buck learns how to adapt in the wild.  Buck's
loyalty to Thornton is once again severed by human cruelty.  This causes him to change
into a being of the wild to forgeo the world of humans, fraught with disloyalty and
dishonor.  The notion of civilization being more uncivilized than any other domain helps
to bring out the changes in Buck.  He understands the rules of the wild as the dreive to
survive is the only adversary.  These rules are clear, while the rules that govern the
world of humanity are far from clear and obscure, at best.  The refined coat he has at
the start of the narrative is replaced by one that is weathered more by survival and the
wild.  This helps to reinforce the emotional change that Buck undergoes, from one who
enjoys what is deemed as luxury to a survival based existence where trial and challenge
exist at every turn.  The lure of the wild in terms of the hunt and the nature of "kill
or be killed" is something of which  Buck becomes a part, fully evolving into the "Ghost
Dog," a being of the wild.