Final answer:
The benefits of bipedalism include freeing hands, increasing energy efficiency, and thermoregulation, while the costs are the anatomical changes required for balance and stability.
Step-by-step explanation:
Bipedalism, walking on two legs, has several benefits and costs compared to quadrupedalism, walking on four legs. The benefits of bipedalism include freeing hands to carry tools, food, or offspring, increasing energy efficiency, and thermoregulation by exposing more of the body's surface. On the other hand, the costs of bipedalism are the anatomical changes required for balance and stability, such as the angling of the femur, spinal curves, and the realignment of the big toe. These changes were necessary to maintain balance while moving on one leg for extended periods of time.