The Mussel– A Not-So-Typical Mollusc

Lab dissection of a representative of Class Bivalvia. Supported by several Shape of Life segments, students interpret bivalve adaptations as a radical case of divergent evolution: A simple ancestral snail with a mobile lifestyle, single dome-shaped shell, bilateral symmetry, and a head (“cephalization”) transformed into a headless, double-shelled, sedentary filter-feeder whose bilateral form is obscure.