A stronger and more specific conclusion would be like this.
The life of Buck rally changed dramatically when he was kidnapped and taken to Alaska to work as a sled dog. Buck has to overcome difficult situations like fighting to Spitz, who was the leader of the dogs, and showed it was capable to lead the group.
Buck has to endure terrible moments of pain in the cold when he was about to die but was rescued by John Thorton, who healed the dog and show it that he really cared.
Yes, Buck had a hard life and tough lessons to learn in Alaska.
This story refers to the novel "Call of the Wild", written by Jack London".