The Paleozoic Era was the start of new life forms with more than one cell. The volcanic activity that went on during this period caused the continents to shift. Making a giant continent called pangea. The climate during this era was warm at first. When the Ordovician era came that started the ice age. Sea levels began to rise causing shallow inland seas. Types of species that could not adapt during this era were mostly land animals. Those animals were giant insects, tetrapods, and other land animals. The event that caused the extinction was the Permian Mass Extinction. The Permian Mass Extinction wiped out the tetrapods and land animals. There were organisms that did survive. Those were the marine organisms.