what is shown by the breakdown of discipline among the team ?

The dogs' teamwork begins to break down. The survival of the team must take priority over his personal struggle with Spitz. Spitz reveals a fundamental weakness when he treacherously attacks Buck. Spitz becomes a threat to the team because he puts his own desires above the team's need. London subtly and masterfully establishes the reader's preference for Buck. This preference is cemented during this fight, as one cannot help but be struck by Buck's greatness.