MESOZOIC EARTH

230 Million Years to 65 Million Years Ago
Mesozoic means "middle life".  The Mesozoic Era began approximately 230 million years ago.  The end of the Paleozoic Era delivered the biggest mass extinction of animals in Earth's history.  The Earth's climate now was very cold and many animals from the Paleozoic Era no longer existed.  In fact, nearly 90% of all ocean animals that could be found during the Paleozoic Era were extinct!  But the good news is many new animal and plant species developed and spread over the land.

The Mesozoic Era is sometimes known as the "Age of Reptiles".  During the Mesozoic Era, reptiles gradually spread throughout the land.  New animal species included dinosaurs, flying reptiles (bird-like animals), early birds and mammals.  Modern alligators, crocodiles, turtles, lizards, and snakes evolved from the early reptiles of this time period.  Plant life changed dramatically during this time.  The land was dominated by large ferns and the  first flowering plants appeared.  New plants called a cycads looked like palm trees and could also be seen throughout the land..

This period's most famous inhabitants are the dinosaurs!  The difference between dinosuars was huge.  Some were very small (about the size of chickens) while others were enormous.  Some were herbivores (plant eaters), some were carnivores (meat eaters) and some were omnivores (plant and meat eaters).  Scientists still disagree as to whether all dinosaurs were cold-blooded.  There has been some evidence that suggests that there were also warm-blooded dinosaurs. 

Throughout this period, new types of dinosaurs appeared while others became extinct.  The reason for the complete disappearance of the dinosaurs approximately 65 million years ago is the biggest mystery in Earth's history.  There are two popular theories explaining the disappearance of the dinosaurs.  Some scientists believe that increased volcanic activity filled the atmosphere with dust and ash.  Sunlight had a hard time getting through such a dirty atmosphere and the Earth became very cold.  As a result many plants died out.  As the plants died out, the plant-eating dinosaurs starved to death.  As the herbivores died out, the meat-eating dinosaurs also lost their food source which caused them to die.  Other scientists believe the dinosaurs disappeared suddenly due to a gigantic asteroid hitting the earth.  The asteroid impact caused fires on the land .  Dust and smoke filled the atmosphere and blocked the sunlight for a long period of time causing widespread destruction to many life forms.  Which one of these theories do you believe?  Or do you have a theory of your own?

Keep reading to learn about the Earth's most recent era - the Cenozoic Era!
Go to:

Home page - Earth's History
Precambrian Era
Paleozoic Era
Cenozoic Era
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