Give An Overview Of Life Through The Tertiary, In Relation To Changing Paleogeography And Climate Essay, Research Paper

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. Ammonoids and marine reptiles disappeared from the sea. Marine taxa that persist as familiar inhabitants of modern ocean, among them bottom dwelling molluscs. On the land, the flowering plants of the Paleogene resembled those of latest Cretaceous time in many ways, but animal life changed dramatically. Taking the place of dinosaurs were the mammals, which were universally small and inconspicuous at the start of the Paleogene interval but in many ways resembled modern mammals by the period s end.

The most profound geographic change during Paleogene time was a refrigeration of Earth s polar regions, which resulted in a chilling of the deep sea and, later in the Cenozoic Era, in widespread glaciation. Paleogene mountain-building events in western North America 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 dramatically too, and humans evolved from apes. The Rocky Mountains and the less rugged Appalachians took shape during the Neogene time, as did the imposing Himalayas. The Mediterranean Sea almost disappeared and then rapidly formed again.

The most widespread physical changes on Earth, however, were climatic. Glaciers expanded across large areas of North America and Eurasia late in Neogene time.

The Paleocene was different climatically from the Mesozoic. For one, it was more temperate around the globe. Secondly it was a lot colder near the poles. Continental drift had slowed down greatly since the Mesozoic, and large seas disappeared off of the continents. The average global temperature was rising and reached a peak in the early Eocene, which was the highest, experienced in the Cenozoic; even the deep seas briefly became warm. Both surface and deep-sea waters near the Antarctic were warmed by about 18 degrees within less than 3000 years. One casualty of these increasing temperatures was the deep-sea species of foraminifera. About 70% became extinct, because the warming terminated the descending cool waters, which provided a vital oxygen supply. New globigerina and star shaped coccolithophores appeared. Mammals diversified and expanded a lot during this Epoch. One of them was Glyptodon, a mammal oddity that evolved in South America. In the seas, sea urchins evolved. Flowering Plants became the major plant of the Cenozoic.

Large “island continents” were still the norm during the Eocene, but they were breaking up and shifting towards their present positions. Such break ups included South America with North America or Australia with Antarctica. This left those continents isolation and made for strange evolution among organisms. The climate in this epoch was relatively warm worldwide, causing a lot of lush swamps and jungles.

Life in the oceans was abundant with new types of wildlife: new fish, crabs, crayfish and the recently evolved whale. Whales probably found their home in the water during this epoch, evolving from hoofed carnivores. Whales took advantage of another food source that had just recently sprung up – plankton.

Land also exploded in new life forms. Penguins, ducks, herons, pelicans and gulls were some of the birds that evolved. Insect newcomers were ants and bees, and poisonous snakes arrived. Mammals also took off: the first bats, bears, tapirs, rhinoceroses, moles, cats, dogs, voles, camels, and rabbits all came into existence. Horses and elephants appeared in this epoch.

The only new plants for this epoch were phytoplankton. This plankton was fed on by zooplankton (tiny plankton animals), which was then fed on by the emerging whales. Dense forests with tropical fauna were up to 50 degrees latitude North and South. The grasslands began to expand.

The climate of the Cenozoic got much cooler during the Oligocene, and Antarctica was freezing up. The more water that froze, the more land was being exposed to dry air. The tropics diminished, giving way to cooler woodlands and grasslands.

Plates were on the move, too. The subcontinent of India was on its way to Asia. Australia and Antarctica parted and cruised away from each other. South America was also on its own.

Due to the increase in grasses, more herbivores appeared. Grasses called for advanced digestive systems, called rumens. Pigs, cattle, deer, and camels were only a few of the mammals that evolved to take advantage of the expanding food source. Cats and dogs evolved to Carnivores during the Oligocene to feast on the new abundance of herbivores.

In South America, since it was separated from the rest of the world, strange developments evolved. Edentates, commonly known as “toothless animals”, emerged. They were animals like sloths, armadillos and anteaters.

Plant life in the Oligocene was similar to flora patterns in other Paleogene epochs. Tropical forests diminished, and grasslands spread around the earth.

Many new mountain ranges were formed during the Miocene. When the African plate pushed against Europe and Asia, the Alps formed. The Rocky Mountains and the Appalachians formed, along with the Himalayas, which where just beginning to form as the subcontinent of India crashed into Asia. Australia and South America remained separated from the rest of the world.

Climate became even colder in a massive “global cooling” that had started in the Oligocene towards the end of the Miocene. Antarctica was smothered in a thick layer of ice in the first glaciers, and sea levels dropped.

As seen by the climate changes going on in this epoch, a cooler planet definitely meant a change in evolution. So, where tropical areas once were, grasslands invaded, taking advantage of the cooler climate. Plankton enjoyed a second radiation, and then declined with the later cooling.

The more grassland there was, the more herbivores roamed the earth. Ruminant herbivores had developed a strategy against the carnivorous mammals that were evolving. They were able to store large ” spare” amounts of food inside themselves. In doing this, they could run away from any predator, and feast on their reserve of food in a safer place. Many other safeguards were developed by these herbivores during the Miocene epoch.

New species included some birds: parrots, woodpeckers, pigeons, and pelicans, falcons, and crows. Mammal newcomers were mice, rats, porcupines, and guinea pigs. Mammal migration between Africa and Asia occurred. Apes also evolved during the Miocene. Their history was found in monkeys, which had evolved since the Paleocene. African primates developed into apes, and eventually into Humans.

During the Pliocene, most landmasses arrived in their present-day positions. The world was also getting a lot colder. Not only had Antarctica grown bigger yet, but an ice cap dominated the northern Arctic, too. This also meant even more invasion of grass. North America and South America connected and a great change in climate occurred. Currents could no longer flow between the two. Warm, Gulf Stream currents could no longer flow to Pacific; they were diverted to North Atlantic.

New and diverse ruminant animals appeared during this epoch. Some animals that were following the forest-to-grass trend were the newly evolved hippopotamuses, gazelles, antelopes, and giraffes that still had short necks.

A major advancement of the mammalian carnivores in this epoch was the “idea” of hunting in packs. This provided many benefits. An obvious advantage is that a very large prey could be killed, even if it was twice the size of any individual pack member. Also, a hierarchy could be organized in each of the social packs. This gave better communication, so the prey could be more easily killed. Apes adapted to Savanna to walk upright and also to the tropical forests.

Plant life’s pattern remained the same as every epoch’s throughout the Tertiary. The cooler the climate, the more grass there was. And the Pliocene was certainly cool.