Final answer:
The femur of a biped is angled inward in comparison to the straight femur of a quadruped. This adaptation, known as the valgus angle, facilitates more comfortable and efficient upright walking for bipeds.
Step-by-step explanation:
The femur of a biped is angled inward in comparison to the straight femur of a quadruped.
This angling, known as the valgus angle, is an important anatomical adaptation that allows bipeds to walk upright more comfortably and efficiently.
Other changes in bipedalism include the evolution of spinal curves, the development of an arch in the foot, and the realignment of the big toe to be parallel to the other toes.