Beginning of Essay
The tertiary consisted of two main epochs. The Paleocene, the Eocene and the Oligocene, which make up the Paleogene; and the Miocene and Pliocene, which make up the Neogene. The close of the Cretaceous Period marked a major transition in Earth’s history. Amm ....

Middle of Essay
.... foreshadowed Neogene uplifts of such ranges as the Sierra Nevada and the Rocky Mountains. During the Neogene, the modern world took shape. The global ecosystems acquired their present configuration and prominent topographic features assumed the forms we are familiar with today. No mass extinction marked the transition from the Paleogene to the Neogene. During the 24 million years of the Neogene, however, life ad Earth’s physical features have changed significantly. The most far-reaching biotic changes were the spread of grasses and weedy plants and the modernization of vertebrate life. Snakes, songbirds, frogs, rats and mice expanded dram ....