Biology Regents Practice Exam 2025 – The All-in-One Guide to Master Your Regents!

The kidneys play a crucial role in maintaining homeostasis in the human body by filtering blood to remove waste products and excess water. They perform this function through a process called filtration, where blood is passed through tiny structures called nephrons. In the nephrons, waste products like urea, toxins, and excess ions are removed from the blood and excreted as urine. Additionally, the kidneys regulate the balance of fluids in the body by adjusting the amount of water that is reabsorbed into the bloodstream or excreted. This process is vital for maintaining the proper concentration of substances in the blood and overall fluid balance in the body.

The other choices do not accurately describe the main functions of the kidneys. Hormone production is not a primary function; while kidneys do produce hormones, such as erythropoietin, their main role is not related to growth. The kidneys do not filter oxygen since oxygen is carried in the blood by red blood cells, not filtered by the kidneys. Lastly, nutrient absorption is primarily managed by the digestive system, not the kidneys. Thus, the kidneys are essential for waste removal and fluid balance rather than the other options suggested.