👉 A variable fluid, often found in biological systems like the circulatory system, is a type of fluid that can change its volume and composition in response to physiological needs. Unlike a constant fluid, such as blood plasma, which maintains a relatively stable composition, a variable fluid can expand or contract to accommodate different volumes of dissolved substances. This adaptability is crucial for functions such as nutrient transport, waste removal, and maintaining osmotic balance. For example, in the kidneys, variable fluids help regulate blood volume and pressure by adjusting the amount of water reabsorbed or excreted. Similarly, in plants, vacuoles within cells act as variable fluid reservoirs that store water and nutrients, allowing the plant to manage its internal environment efficiently.
