1. At this point in "The Lord of the Flies," the boys have created a set of rules and have begun a system necessary for survival. Ralph has been voted chief and wants the boys to work on collecting food, building shelters, keeping the fire going (the hunter's job), etc. Ralph is upset because the hunters know their responsibility, yet went off to go swimming before doing their work.
2. Part of what William Golding is questioning in the novel is man's tendency for savagery. When Jack and hunters begin acting like hunters, they are becoming transformed and descending into darkness. Jack and the hunters begin taking on animal-like qualities, and cannot rid themselves of their savagery:
"He [Jack] tried to convey the compulsion to track down and kill that was swallowing him up. 'I went on. I thought, by myself—'
The madness came into his eyes again. 'I thought I might kill.'" (Chapter 3)
3. The basic cause of this disagreement is that Ralph feels that Jack and his hunters are not pulling their weight. Jack feels like he needs to contribute to the group in a way that provides as much validation as being chief (Ralph's job). Since Jack is not as good of a hunter yet, he is quick to be defensive.