The Paleozoic Era was a prehistoric period in earth's history that ran for about 290 million years. The University of California Museum of Palaeontology reports that the beginning of the Paleozoic Era was defined by an explosion of species diversity as multicelled animals began to evolve into different species. The Paleozoic Era ended with a mass extinction event that wiped out about 90 percent of all these new species.
Live Science explains that the Paleozoic Era is further divided into six periods, each of which was tens of millions of years in length. The first was the Cambrian Period, during which the first animals with spinal columns appeared. During the second, the Ordovician Period, many new fish and marine invertebrate species appeared. This process continued in the Silurian Period, during which time more species of fish also appeared. The fourth, the Devonian Period, was the first time animals emerged from the sea to live exclusively on land.
Further explained by Live Science is how species continued to evolve at a rapid in the second half of the Paleozoic Era. During the Carboniferous Period, animals that could lay eggs on land evolved, allowing them to further distance themselves from the water. Finally, during the Permian Period, life on land divided into herbivorous and carnivorous species.