The Paleozoic Era was arguably the longest era of all time. During this era, tons of life had come into the play. At first, mollusks, arthropods, and fish had dominated the seas. However, soon enough, the arthropods had scuttled out of the water to live on land, while the fish had undertaken a long line of evolution into amphibians, which were also able to exit the water. During this colonization, plants had started to rise on the land, soon growing into trees. After the first colonization of land, the amphibians undertook a long line of evolution into reptiles, and the first conifers formed. However, a destructive mass extinction had culminated the Paleozoic, and the Earth took a long time to recover. However, the reptiles continued to dominate, and soon evolved.