The structure in the ear responsible for balance is called the vestibular system, which includes the semicircular canals, utricle, and saccule. These components detect changes in the position and motion of the head, sending signals to the brain that help maintain equilibrium. The semicircular canals are particularly sensitive to rotational movements, while the utricle and saccule respond to linear accelerations and gravitational changes. Proper functioning of the vestibular system is essential for coordination, stability, and posture, contributing to an organism's ability to navigate its environment effectively.