Excretory Products and Their Elimination — Class 11 Biology NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 11 Biology chapter "Excretory Products and Their Elimination" — 8 important questions with detailed answers for CBSE board exam preparation.

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TL;DR: Free step-by-step NCERT solutions for Class 11 Biology chapter "Excretory Products and Their Elimination" — 8 important questions with detailed answer…

Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated Jul 23, 2026

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Key Questions Covered:

Define excretion. Why is it necessary for living organisms?
Name the main nitrogenous wastes in humans and their sources.
Draw and label a nephron. What are its main parts?
Explain the three processes involved in urine formation.
What is the role of ADH and aldosterone in osmoregulation?
What is the difference between a pyramid of energy and a pyramid of biomass?
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
Define excretion. Why is it necessary for living organisms?	✓ Solved
Name the main nitrogenous wastes in humans and their sour…	✓ Solved
Draw and label a nephron. What are its main parts?	✓ Solved
Explain the three processes involved in urine formation.	✓ Solved
What is the role of ADH and aldosterone in osmoregulation?	✓ Solved
What is the difference between a pyramid of energy and a …	✓ Solved

Showing 6 of 8 questions

Q1: Define excretion. Why is it necessary for living organisms?

Excretion is the process of removing metabolic waste products from the body. It is necessary because: - Prevents accumulation of toxic waste like urea, uric acid, and CO2 - Maintains internal osmotic balance and pH - Prevents damage to cells and tissues - Helps maintain homeostasis

Q2: Name the main nitrogenous wastes in humans and their sources.

Main nitrogenous wastes: - Urea: formed from breakdown of amino acids and proteins in liver; most common in humans - Uric acid: end product of nucleic acid metabolism; requires water for excretion - Ammonia: toxic, produced during amino acid catabolism; converted to urea in liver

Q3: Draw and label a nephron. What are its main parts?

Main parts of nephron: - Renal corpuscle: Bowman's capsule + glomerulus (filtration) - Proximal convoluted tubule: selective reabsorption of glucose, amino acids, ions - Loop of Henle: creates concentration gradient for water reabsorption - Distal convoluted tubule: fine-tuning of reabsorption - Collecting duct: final concentration of urine, water reabsorption via ADH

Q4: Explain the three processes involved in urine formation.

Three-stage process: - Ultrafiltration: in Bowman's capsule; high blood pressure forces small molecules (glucose, urea, ions, water) through glomerular filtration barrier; large proteins and RBCs remain in blood - Selective reabsorption: useful substances reabsorbed in PCT (glucose, amino acids, 80% ions, 85% water) - Tubular secretion: additional wastes secreted from blood into tubule lumen for concentration; occurs in DCT and collecting duct

Q5: What is the role of ADH and aldosterone in osmoregulation?

ADH (antidiuretic hormone): - Released by pituitary when blood osmotic pressure increases - Increases permeability of collecting duct to water - More water reabsorbed, concentrated urine formed Aldosterone: - Secreted by adrenal cortex - Increases reabsorption of Na+ and water - Maintains blood pressure and Na+ balance

Q6: What is the difference between a pyramid of energy and a pyramid of biomass?

Energy pyramid: - Always upright; each trophic level has less energy than the one below - Energy loss at each transfer (~10% rule) - Cannot be inverted Biomass pyramid: - Usually upright but can be inverted - In aquatic ecosystems, small algae support large zooplankton - Biomass does not directly relate to energy content

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