MPE - Cenozoic Era Lesson

 

Cenozoic Era

The most current era, the Cenozoic Era, spans 65 million years and is broken up into two periods: Tertiary and Quaternary. Each of these periods is divided into several Epochs. This era is often known as "The Age of Mammals" because some of the largest land mammals ever lived during this time. Warm-blooded mammals began to evolve after the Cretaceous mass extinction.  Body hair as well as complex lungs and hearts allowed them to adapt and thrive in their new environment. Mammals could survive in very cold and hot climates, so they were able to span all land areas. Mammals were one of the dominant life forms during the Cenozoic era.

Tertiary Period - 65 to 2 million years ago

This period consists of six epochs: the Paleocene, Eocene, Oligocene, Miocene, and Pliocene. Each epoch has unique characteristics because the climate and geography changed for each one. In turn the plants and animals evolved to meet these changes.

During the Tertiary period, Pangaea began to break apart and form the continents that exist today. Tectonic plates collide to form the Alps, the Rockies, and Himalayas mountain ranges. The beginning of this period was warm and the plants were very similar to what we have today. There were many dense forests and tropical plants everywhere. Evidence shows us that palm trees once grew in Greenland!   As the climate grew cooler, open woodlands and grasslands became prominent which supported large groups of herding and grazing animals.  The global climate continued to become cooler and drier causing glaciers to begin to form in Antarctica as the temperatures across the world began to decrease and because of its new location. This continued until an ice age began in the Pliocene Epoch.

The extinction event at the end of the Cretaceous Period wiped out dinosaurs, which left room for other species to evolve and fill the niches left by dinosaurs. Many new species of animals evolved in the oceans and on land.  Fossil records provide evidence of the first whale, flying squirrels, bats, pigs, and camels. Most mammal groups were present by the Eocene Epoch.  The first hominids appeared during the Pliocene Epoch.

This period was also successful for other animals. Birds did as well as mammals increasing in diversity including more flightless birds that are now extinct.  New fish species, including trout and bass, and sharks became numerous.   Plants did as well as animals in evolving to fill new ecological niches. As flowering plants evolved and spread across the globe, insects evolved to be able to eat the nectar and pollen provided by the various plants. Ninety-five percent of all modern seed plants evolved during the Miocene Epoch.

The tertiary period ended with an ice age and land bridges. As the global temperature kept dropping, this led to huge glaciers at the poles of the Earth. Glaciers covered most of the earth's mountain ranges, including the newly formed Himalayas and Alps. As the Earth cooled and more water locked in as ice, land bridges appeared:

• Between Asia and North America
• Great Britain and Europe
• South East Asia and Borneo

These land bridges allowed for the migration of plants and animals from one continent to another. The tertiary period ended in this cold dry ice age.

Quaternary Period - 1.8 millions years ago to present day

The quaternary period, often called the "Age of Humans", is the current time period in the Geologic Time Scale. The current period is divided up into two epochs, Pleistocene and Holocene each with their own climate and geographic characteristics, so the animals and plants that are most prevalent are unique to each epoch too.

During this period, the continents that we have today settled into their current positions.  The climate during this time changed to be cooler which include the formation of bigger sheets of ice. This cooler temperature was not consistent, with several periods of warming and then cooling again. Scientists have evidence of over 60 cycles of glacial expansion and retreat during the Pleistocene Epoch. These variations in temperature are probably due to the Earth's orbiting. The last major glaciations event was over 18,000 years ago.

As the ice expanded, this allowed land once covered by water to be exposed. One such bridge, the Bering land bridge between Alaska and Siberia, allowed for migration of all life forms.

Many plants and animals from today are the same as the Quaternary period with some important differences. Animals then were well adapted for cold weather developing thick fur including wooly mammoths, mastodons, and wooly rhinoceros. When the Earth's temperatures began to warm, many of these animals became extinct.

The Pleistocene Epoch is known as the ''giant mammals" or megafauna.  Along with the wooly mammoth and mastodon, there were other giant mammals including bison, bears, sloths, and deer. As animals became bigger, giant carnivores also evolved including the saber tooth tiger. By the end of this epoch, megafauna disappeared leaving behind current smaller species including elephants, rhinoceros, and hippopotamus.

 

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