by DianeD

Created on: April 06, 2009

The earth was a much different place 65 to 150 million years ago when dinosaurs roamed the earth. Many changes in the planet's climate, along with geological transformations, occurred during the Triassic, the Jurassic, and the Cretaceous periods of the Mesozoic Era, also known as the Age of the Reptiles. Each period presented new species of plants, marine life, and land animals, as species that could not adapt to each new environment became extinct; however, what could have possibly caused a worldwide eradication of life at the end of the age?

At the latter part of the Cretaceous period, dinosaurs had become massive. Plant life flourished providing a healthy diet for the herbivores; in turn, the carnivores were supplied with an endless supply of meat to sustain their enormous size. The food chain was complete with a tropical environment; then, it all ended. Once thought to have been an almost instantaneous extinction, paleontologists have now determined that many factors may have contributed to the mass extinction.

Although mass extinctions are not common, scientists believe they have only occurred five times during the earth's history. For example, during the Permian Period of the Paleozoic Era, just preceding the Mesozoic Era, 95% of all marine life and 70% of all land life disappeared. A drastic climate change at the time has been credited with the extinction. In the late Devonian period, a mere 370 million years ago, life also suffered a likewise demise; the cause has not yet been determined.

Paleontologists today believe the dinosaur extinction was not due to one catastrophic event, but that the extinction took place over many years and caused by numerous contributing events. Severe climate changes had occurred over the years. Since the climate has everything to do with proper plant growth, plant eating species experienced famine as food sources became scarce. This would also have affected the meat eating species, as the food chain became interrupted.

In the few short years that man has lived on the planet, plagues have caused millions of deaths. With the changing world million of years ago, disease could have played a significant role in the elimination of some species. Though this theory would have probably taken place over a long period of time, dinosaur populations would have been infected and gradually decreased.

It is also important to understand that the earth itself was undergoing extreme physical changes during the era. The earth's tectonic plates

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