I think one of the key quotes of this great short story that introduces the central conflict between the individual and nature comes towards the beginning of the story after we have had our initial introduction to "the man." Of course, you might like to think about why London leaves "the man" nameless and only refers to him in this way--that in itself seems to suggest the insignificance of man against the might of nature. However, consider the following quote:

Fifty degrees below zero meant eighty-odd degrees of frost. Such fact impressed him as being cold and uncomfortable, and that was all. It did not lead him to meditate upon his frailty as a creature of temperature, and upon man's frailty in general, able only to live within certain narrow limits of heat and cold, and from there on it did not lead him to the conjectural field of immortality and man's place in the universe.

Note how the arrogance and limited vision of the man is referred to. He accepts that it is cold, but is blind to the wider consequences of the tremendous power of nature, ignoring his "frailty" as a human being and suggesting his belief that he can survive in any situation. The man is shown to disregard nature as a separate, powerful entity that is able to kill him. It is this arrogance that costs the man his life.