I don't want to do your assignment for you, but I will give you some guidance. Piggy is a character with great symbolism. He stands for the intellect, the thinking part of people. Piggy is always thinking things through, in fact, he often is reluctant to act because he is so busy mulling over matters. Piggy is chubby because of this slowness to action. Piggy's glasses are also part of this intellect symbolism. The glasses are used to start fire and the ability to make fire is generally considered what separates man from animals. Man has the intelligence to make fire whereas animals do not. That fire is allowed to get out of hand shows that the boys on the island let civilization, or the lack of it, get out of hand. Piggy shows his intelligence from the beginning to the end. At the start of the story, he suggests to Ralph that a conch shell, if blown into in the right way, will yield a loud sound. That loud sound draws all the boys near so it becomes the tool by which the boys are gathered and it is used in meetings to allow one to speak, therefore it becomes symbolic of order and civility. Piggy is holding the conch shell in chapter 11 when Roger rolls the boulder off the top of Castle Rock onto Piggy, crushing both the conch shell and Piggy's skull simultaneously. This crushing of Piggy and the conch signifies the end of all intellect and civility on the island. Piggy tells Ralph that he isn't sure about the existence of the beast because it isn't logical for there to be a beast. Piggy shows insight, too, when he tells Ralph that Jack would hurt him (Piggy) if Ralph weren't there. Piggy's last act, in chapter 11, is to try to reason with Jack and his tribe.