1. The earliest dinosaurs and mammals evolved at approximately the same time. Why do you think dinosaurs were better able to achieve prominence in the Mesozoic than were mammals?
2. Teleost fishes, sharks, ichthyosaurs, and other aquatic animals all developed broadly similar body forms. What characteristics of this general body form make it adaptive for life in the water? Have any flying animals evolved similar body forms, and if so, why?
3. What characteristics of the body and trace fossil records of dinosaurs might you expect to provide clues as to whether dinosaurs were slow, lumbering animals or more active ones?
4. Was the end of the Cretaceous Period the only time in Earth history when a large bolide struck Earth? What is the likelihood of it happening again? How might an asteroid impact affect the world today?
What is happening in these pictures
The ginkgo, a gymnosperm with ancient evolutionary roots.
Fossil ginkgo leaves (left). Ginkgos were common enough in the Mesozoic Era to serve as an important food source for animals.
Modern ginkgo leaves (right). Today, ginkgos are represented by only one species, Ginkgo biloba. Humans use the seeds as food.
What distinguishes the ginkgo as a gymnosperm?
How much have ginkgos changed since the Mesozoic Era?
World History
