Osmoregulation refers to which biological concept?

• A. Regulation of the body's temperature by sweating and shivering.
• B. Regulation of water and solute balance within an organism or cell.
• C. Regulation of oxygen uptake in the lungs.
• D. Regulation of nutrient absorption in the gut.

Answer: (B)

Osmoregulation is about controlling water and solute balance within an organism or cell. Living systems face different external environments and must keep internal water potential and solute concentrations within narrow limits to keep cells functioning properly. This involves mechanisms that adjust how much water is taken in or lost and how salts and other solutes are transported or excreted, such as kidney function and hormonal control of urine concentration. The other ideas describe different regulatory problems: regulating body temperature is thermoregulation, regulating oxygen uptake is part of respiration/gas exchange, and regulating nutrient absorption concerns digestion and nutrient uptake. So the concept being tested is the regulation of water and solute balance within the organism or its cells.