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Excretory Products and their Elimination

CBSE · Class 11 · Biology

Quick revision notes for Excretory Products and their Elimination — CBSE Class 11 Biology. Key concepts, formulas, and definitions for last-minute revision.

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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?
Excretory Products and their Elimination covers several key topics that are frequently asked in CBSE Class 11 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Excretory Products and their Elimination — CBSE Class 11 Biology?
Understand the core concepts first, then work through the 124 practice questions available for this chapter. Revise formulas and 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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