curly's death teaches buck...,What?

Curley's death teaches Buck how to stay alive, it teaches him about the law of club and fang.

Three men with clubs were helping him to scatter them. It did not take long. Two minutes from the time Curly went down, the last of her assailants were clubbed off. But she lay there limp and lifeless in the bloody, trampled snow, almost literally torn to pieces, the swart half-breed standing over her and cursing horribly. The scene often came back to Buck to trouble him in his sleep. So that was the way. No fair play. Once down, that was the end of you. Well, he would see to it that he never went down. Spitz ran out his tongue and laughed again, and from that moment Buck hated him with a bitter and deathless hatred.