The conch shell becomes a powerful symbol of civilisation and order in the novel, and it also represents democracy. However, when Jack rebells and other kids followed him, democracy (the conch) is diminished. By the time Roger rolled a huge bolder and killed Piggy as well as the conch, it signifies the demise of the civilised instinct among almost all the boys on the island.
But I tell you there isn't a beast !!!
Piggy is the most intelligent, rational boy in the group, and his glasses represent the power of science and intellectual endeavor in society. This symbolic significance is clear from the start of the novel, when the boys use the lenses from Piggy’s glasses to focus the sunlight and start a fire. When Jack’s hunters raid Ralph’s camp and steal the glasses, the savages effectively take the power to make fire, leaving Ralph’s group helpless.
The fire symbolizes the only hope to be rescued, the brightness, which is why Ralph keeps on telling ack to keep the fire going. But later it turns out to become the disaster of the island and especially of Ralph.
The imaginary beast that frightens all the boys stands for the primal instinct of savagery that exists within all human beings. The boys are afraid of the beast, but only Simon reaches the realization that they fear the beast because it exists within each of them. As the boys grow more savage, their belief in the beast grows stronger. By the end of the novel, the boys are leaving it sacrifices and treating it as a totemic god.