Which of the following enables mammals to maintain balance?

Step 1: Analyze the question The question asks which part of the mammalian ear is responsible for balance (equilibrium), not hearing.

Step 2: Explain the concept The ear has three regions, each with its own job:

• Outer ear: collects sound (pinna, ear canal).
• Middle ear: carries sound vibrations (tympanic membrane/eardrum, ossicles, Eustachian tube).
• Inner ear: has the cochlea for hearing, and the semi-circular canals, utricle and saccule for balance.

Step 3: Check each option

• A. Cochlea: converts sound vibrations into nerve impulses. This is for hearing, not balance.
• B. Eustachian tube: connects the middle ear to the throat and equalizes air pressure on both sides of the eardrum.
• C. Ossicles: the three small bones (malleus, incus, stapes) that amplify and pass on vibrations.
• D. Semi-circular canals: three fluid-filled canals set at right angles to each other. When the head moves, the fluid (endolymph) moves and stimulates sensory hair cells, which send impulses to the brain about the position and movement of the head. This maintains balance.
• E. Tympanic membrane: the eardrum, which vibrates when sound hits it. This is for hearing.

Step 4: Answer The semi-circular canals detect head rotation and position, so they enable mammals to maintain balance.

Tip: Remember "Cochlea = Catches sound" (hearing) and "Semi-circular canals = Stay steady" (balance). Whenever a question mentions balance or equilibrium, think of the semi-circular canals, utricle and saccule.