Class 11 Biology Notes: Excretory Products and Their Elimination | NCERT Summary, Human Kidney, Nephron, Urine Formation, Hormonal Regulation, Disorders
Overview: Chapter – Excretory Products and Their Elimination 1. Types of Nitrogenous Wastes Animals excrete three main types: Ammonia – excreted by ammonotelic organisms like aquatic animals; highly toxic, requiring large water quantities . Urea – excreted by ureotelic organisms such as mammals (including humans), amphibians; less toxic and water-efficient . Uric acid – excreted by uricotelic organisms like birds, reptiles, insects; least toxic and conserves water . 2. Human Excretory System Composed of kidneys, ureters, urinary bladder, and urethra . Functional units in kidneys are nephrons—each kidney has about 1 million . 3. Urine Formation Mechanisms Glomerular filtration – filters blood into Bowman’s capsule (protein-free fluid) . Tubular reabsorption – reclaims needed substances. Tubular secretion – removes excess ions, ammonia, etc. . 4. Countercurrent Mechanism The loop of Henle and vasa recta create osmotic gradients in the medulla (300 to 1200 mOsmol/L), allowing concentratio...