Which term describes the left-right mirror-image arrangement along the body?

• A. Bilateral symmetry
• B. Radial symmetry
• C. Asymmetry
• D. Spiral symmetry

Answer: (A)

Symmetry in organisms refers to how body parts are arranged around an axis. A left-right mirror-image arrangement along the body is bilateral symmetry. In bilateral symmetry, a midsagittal plane divides the body into left and right halves that are essentially mirror images. This arrangement supports a defined head (anterior) and tail (posterior) and often links to forward-directed movement and sensory organization at the front.

Radial symmetry would mean there are many planes of symmetry around a central axis, like spokes on a wheel, typical of organisms such as jellyfish. Asymmetry lacks a consistent, mirror-image plan. Spiral symmetry describes a spiral pattern, such as in some shells, not a straight left-right division. So the term that fits the description is bilateral symmetry.