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Excretory Products and their Elimination — Revision Notes

CBSE · Class 11 · Biology

Excretory Products and their Elimination revision notes for CBSE Class 11 Biology: 4 topics in quick points. Part of the CBSE Class 11 Biology syllabus.

124 questions80 flashcards2 formulas & key relations5 concepts

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Key Topics to Revise

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1. Nitrogenous Wastes and Excretory Structures in Animals

  • Ammonia, urea, and uric acid are the major nitrogenous wastes excreted by animals.
  • Ammonia is the most toxic form and needs a large amount of water for elimination, while uric acid is the least toxic and needs minimum water.
  • Ammonotelism means excretion of ammonia; it is seen in bony fishes, aquatic amphibians, and aquatic insects.
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2. Human Excretory System

  • The human excretory system consists of a pair of kidneys, a pair of ureters, a urinary bladder, and a urethra.
  • Kidneys are reddish brown, bean-shaped organs located between the last thoracic and third lumbar vertebra close to the dorsal inner wall of the abdominal cavity.
  • Each adult kidney measures 10-12 cm in length, 5-7 cm in width, 2-3 cm in thickness, and weighs about 120-170 g.
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3. Urine Formation: Filtration, Reabsorption, and Secretion

  • Urine formation involves three processes: glomerular filtration, reabsorption, and secretion.
  • On average, 1100-1200 ml of blood is filtered by the kidneys per minute, which is roughly one-fifth of the blood pumped by each ventricle per minute.
  • Blood filtration occurs through three layers: endothelium of glomerular blood vessels, epithelium of Bowman’s capsule, and the basement membrane between them.
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4. Function of the Tubules

  • The proximal convoluted tubule is lined by simple cuboidal brush border epithelium, which increases surface area for reabsorption.
  • Nearly all essential nutrients and 70-80% of electrolytes and water are reabsorbed in the PCT.
  • PCT also secretes H+ and ammonia and absorbs HCO3- to help maintain pH and ionic balance.

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Full Notes

Key Concepts

AmmoniaAmmonotelism is excretion of ammoniaProtonephridia or flame cells occurThe human excretory system includes twoA nephron is the functional

Frequently Asked Questions

What are the important topics in Excretory Products and their Elimination for CBSE Class 11 Biology?
Key topics in Excretory Products and their Elimination include Nitrogenous Wastes and Excretory Structures in Animals, Human Excretory System, Urine Formation: Filtration, Reabsorption, and Secretion, Function of the Tubules. Study these first, then practise questions on each for Class 11 exams.
How should I revise Excretory Products and their Elimination for Class 11 exams?
Learn the core ideas first, then work through the 124 practice questions on Excretory Products and their Elimination. Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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