El Paleozoico se divide en seis períodos: Cámbrico (la vida animal florece en los mares), Ordovícico (dominan los invertebrados), Silúrico (primer animal de respiración aérea), Devónico (aparecen peces con escamas duras y los anfibios), Carbonífero (aparecen grandes bosques de helechos, primeros reptiles etc,
Esperanza grows and matures in several ways. At the beginning of the novel, she is a wealthy girl without a trouble in the world and is largely ignorant to the problems of people around her. She is forced to leave behind everything she knows and overnight, goes from a carefree young girl to a desperate migrant worker.
