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Osmosis is the diffusion of water through a selectively permeable membrane. Given their size and availability, the hard exterior shell of eggs provide a convenient macro-scale model of the system-level phenomenon of osmosis. Once the shell of a fresh, uncooked chicken egg is removed in an acid bath, the egg’s intact, selectively permeable cell membrane is elastic enough to noticeably swell and shrink without bursting in response to changing osmotic pressure. In this activity, students will see how the “Naked” egg-solution system demonstrates how constancy and change define biological systems. This free selection includes the Table of Contents, Introduction, a Science Education Topics section, and the Index.