Final answer:
A jack rabbit's powerful leg is a structural adaptation, crucial for locomotion and evasion of predators, highlighting an evolved physical feature that aids in their survival.
Step-by-step explanation:
A jack rabbit’s powerful leg is an example of a structural adaptation. In biology, structural adaptations are physical features of an organism, like the anatomy, that have evolved over time to allow for better survival in its environment. These contrasts with functional adaptations, which are related to the way an organism's body works, and behavioral adaptations, which involve the way an organism behaves. Rabbits and hares, classified as lagomorphs, have evolved particularly strong hind limbs that provide for a bouncing method of locomotion, which is essential for quick escape from predators. This characteristic feature is an integral part of their structure and crucial for their survival in the wild.