The Mesozoic Era was the time of the dinosaurs. The first dinosaurs appeared about 225 million years ago. About this same time, Pangaea began to break up. The first mammals, which evolved from warm-blooded reptiles, also appeared in the Mesozoic. Many areas had a warm, wet climate. Another major development was the appearance of flowering plants.
All the dinosaurs and many other types of organisms were killed at the end of the Mesozoic Era. What caused this mass extinction?
Figure 36 This spiral diagram provides an overview of Earth's history. Start at the bottom left, which begins with Earth's formation approximately 4. 6 billion years ago. Then follow the spiral upward to see many of the major events in the history of life and geology on Earth. Interpreting Diagrams During what era did small mammals first appear?
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