Model 2 illustrates osmosis in animal and plant cells, showing how water moves across selectively permeable membranes in response to solute concentrations.

Final Answer:
8. a. Both animal and plant cells have a selectively permeable membrane.
b. Only plant cells have a permeable, rigid cell wall.
9. The thickness of the arrow indicates the rate or amount of water moving — thicker arrow = more water movement.
10. (Without diagrams A–F, this cannot be answered definitively; but generally:)
a. Cells in hypotonic solution gain water → net increase.
b. Cells in hypertonic solution lose water → net decrease.
c. Cells in isotonic solution → no net change.
11. a. In a hypertonic solution, the plant cell loses water → cytoplasm shrinks away from cell wall (plasmolysis).
b. In a hypertonic solution, the animal cell loses water → shrivels (crenation).
12. a. In a hypotonic solution, the plant cell gains water → becomes turgid (firm), but does not burst due to cell wall.
b. In a hypotonic solution, the animal cell gains water → swells and may burst (lysis).
13. The rigid cell wall of the plant cell prevents it from bursting — it resists expansion and maintains shape.
14. Without knowing the solute concentration inside the Elodea cell, we cannot determine definitively — but typically, 5% NaCl is hypertonic relative to plant cell cytoplasm, so likely hypertonic.