Students say "GFR = 125 mL/min means 125 L/day urine." Wrong: GFR × 1440 min = 180 L/day of FILTRATE. Urine = 1.5 L/day (only 0.83% of filtrate). 99% is reabsorbed.

Students swap loop of Henle permeability: they say descending = NaCl-permeable, ascending = water-permeable. It is exactly reversed: descending = water-permeable (not solutes); ascending = NaCl-permeable (not water).

Students say all frogs are ammonotelic. Wrong: TADPOLES = ammonotelic (aquatic). ADULT FROGS = ureotelic (terrestrial). The life stage and habitat determine the mode.

Students say marine fish are ammonotelic because they are aquatic. Wrong: Marine (saltwater) bony fish are UREOTELIC because seawater is hyperosmotic — they lose water by osmosis and cannot afford the extra water loss needed to excrete ammonia.

Students say ADH is produced in the posterior pituitary. Partially wrong: ADH is SYNTHESIZED in the hypothalamus (supraoptic and paraventricular nuclei). It is stored and RELEASED from the posterior pituitary.

Students say ANF is released when blood volume is LOW (same trigger as RAAS). Wrong: ANF is released when blood volume is HIGH (atrial stretching). RAAS is triggered when volume is LOW. They have opposite triggers and opposite effects.

Students say the ornithine cycle occurs in the kidney. Wrong: The ornithine cycle (urea synthesis) occurs in the LIVER. The kidney only filters and excretes the urea transported to it from the liver.

Students say dialysing fluid contains no glucose or amino acids. Wrong: Dialysing fluid DOES contain glucose and amino acids at normal plasma concentrations to prevent them from diffusing out of the patient's blood.

Students mix up aldosterone and ADH effects: Aldosterone = Na+ in, K+ out (DCT). ADH = water reabsorption (DCT + collecting duct). ADH does NOT affect electrolytes directly.

Students say vasa recta creates the medullary gradient. Wrong: The LOOP OF HENLE creates (multiplies) the gradient. The vasa recta only maintains (exchanges) it without washing it away.