What Is Life? 2nd Edition by Jay Phelan

Exercise 11

The cheetah is an amazingly fast cat that hunts its prey on the African savannas, sprinting for short distances at speeds approaching 70 miles per hour. The sloth in the Amazon rain forests of South America is a very slow creature that hangs from a tree by all four limbs and eats vegetation. How can this difference-that the cheetah can sprint at high speeds, while the sloth moves almost in slow motion-be explained in evolutionary terms? What modifications might occur to the cheetah's ability to run if it were to occupy the same niche as the sloth, assuming the cheetah had no natural enemies there?