In "Lord of the Flies," why does Jack not like Ralph in the first place?

Jack and Ralph's rivalry begins when the boys are first stranded on the island. As the boys try to pick a leader from the group, Jack says, "I ought to be chief . . . because I'm chapter chorister and head boy. I can sing C sharp." Jack believes his status in the choir sets him up for leadership on the island. The other boys, however, disagree. They are drawn to Ralph's "stillness," "size," "attractive appearance," and the fact that he is holding the powerful conch shell. The boys take a vote, and Ralph wins. Ralph tries to smooth things over by saying that Jack can take "charge of the choir," but the groundwork for their conflict has been established.