Final answer:
Organisms use tonicity to regulate water flow across cell membranes, allowing them to maintain stable internal conditions. In a hypotonic solution, water enters the cell, risking swelling and bursting, while in a hypertonic solution, it leaves, causing the cell to shrink. The goal is to achieve an isotonic state with no net water movement.
Step-by-step explanation:
Organisms use tonicity to maintain homeostasis by controlling the movement of water across their cell membranes. When a cell is placed in a hypotonic solution, which has a lower concentration of solutes than inside the cell, water will flow into the cell. This could cause the cell to swell and potentially burst, so to prevent this, various mechanisms may be employed by the organism to expel this excess water or to prevent its entry and maintain the isotonic state, where the solute concentration is equal inside and outside the cell, and there is no net water movement.
In contrast, in a hypertonic environment where the extracellular fluid has a higher concentration of solutes, water will leave the cell causing it to shrink. Here, organisms may adapt by taking up water or solutes to equilibrate the osmolarity and achieve an isotonic environment. These balancing acts are critical for the survival of cells in different environments and are a key aspect of homeostasis.