Chapter 27, Problem 9TYU

FOCUS ON ORGANIZATION

Early tetrapods had a sprawling gait, like that of a lizard: As the right front foot moved forward, the body twisted to the left and the left rib cage and lung were compressed; the reverse occurred with the next step. Normal breathing, in which both lungs expand equally with each breath, was hindered during walking and prevented during running. In a short essay (100-150 words), explain how the origin of dinosaurs, whose gait allowed them to move without compressing their lungs, could have led to emergent properties in biological communities.