The conch symbolizes civilization, more specifically, rules and structure. In the beginning of the book when everyone is focused on civilization and rescue, the conch has the ultimate authority. As the book goes on and the boys become savages, the conch loses its power and the boys lose their hope for rescue and returning to civilization.
Piggy was the voice of reason on the Island and for a time the voice for ace, so In that sense his glasses were representative of his seeing things more clearly than the others as opposed to returning to a more preemptively attitude Like the other boys. Since they used his glasses as the primary means of making fire on the Island they were also a symbol of power. The boys used fire to stay warm, to keep away the beast and to cook food, so It was very Important. Whomever controlled fire had the power.
The fire represents life and death at the same time. They need the ire to stay alive and civilized as they use it as a smoke signal to attract rescuers. It acts as a symbol of death at the end when the boys set the forest on fire and try to destroy their own lives and the life of Simon. “Kill the beast, cut his throat, spill his blood” is the tribes chant when hunting. This is significant because all the boys go into a tribal mentality and in a trance when they chant this and dance. This is why the boys mistake Simon as the Beast and murder him.
The quote itself is symbolic of unanimity left to its own devices. No matter how refined our society is, when it all boils down, we will overrule class and “training” to act out in a savage manner and move towards an overthrow of society and structure. The boys Just wanted to be rescued and in the end, they all ended up becoming savages and only aware of themselves. They all turned into evil little kids and were more aware of their primitive behavior. They were living on an island, so they all started acting like animals that were living there first.