Class 11 Biology Chapter 16 Excretory Products and Their Elimination Solutions (Exercise Questions)
The complete exercise and in-text answers are given below. Studying through Class 11 Biology Chapter 16 Excretory Products and Their Elimination question answer helps students revise important concepts. These solutions are based on the latest NCERT curriculum and help in quick revision before exams.
Q1. Define Glomerular Filtration Rate (GFR)
Answer: The Glomerular Filtration Rate (GFR) is a measure of how well the kidneys filter the blood.
- GFR is the rate of fluid filtered by all of the nephrons in both kidneys per minute.
- Normal GFR in healthy adults is roughly 125 mL/min (180 litres per day).
Q2. Explain the autoregulatory mechanism of GFR.
Answer: The kidneys contain a systematic mechanism to control GFR through the Juxtaglomerular apparatus (JGA).
- The JGA senses reduced GFR and releases renin, activating the renin-angiotensin system to cause vasoconstriction and increase blood pressure.
- This action restores glomerular filtration pressure, bringing GFR back to normal.
Q3. Indicate whether the following statements are true or false:
(a) Micturition is carried out by a reflex.
(b) ADH helps in water elimination, making the urine hypotonic.
(c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule.
(d) Henle’s loop plays an important role in concentrating the urine.
(e) Glucose is actively reabsorbed in the proximal convoluted tubule.
Answer: The true and false statements are mentioned below:
Statement | True/False |
(a) Micturition is carried out by a reflex. | True |
(b) ADH helps in water elimination, making the urine hypotonic. | False |
(c) Protein-free fluid is filtered from blood plasma into the Bowman’s capsule. | True |
(d) Henle’s loop plays an important role in concentrating the urine. | True |
(e) Glucose is actively reabsorbed in the proximal convoluted tubule. | True |
Q4. Give a brief account of the counter-current mechanism.
Answer: The countercurrent mechanism plays a crucial role in the concentration of urine and water conservation.
- It maintains a medullary osmotic gradient (300 → 1200 mOsm/L).
- The Loop of Henle removes NaCl (ascending limb) while urea recycling from the collecting duct also contributes. The vasa recta preserves this gradient by countercurrent exchange.
Q5. Describe the role of the liver, lungs and skin in excretion
Answer: Various organs contribute to the excretion processes of the body, each with distinct functions.
| Organ | Role |
|---|
| Liver | Converts ammonia to urea and excretes bile pigments/drugs. |
| Lungs | Remove carbon dioxide through exhalation. |
| Skin | Sweat glands excrete water and salts; sebaceous glands secrete oils. |
Q6. Explain micturition
Answer: Passing urine out of the bladder is called Micturition
- As the urine builds up, bladder stretch initiates a spinal reflex, the urethral sphincters relax, and the muscles of the bladder contract.
- Adults typically urinate approximately 1–1.5 litres per day.
Q7. Match the items of column I with those of column II
Column I Column II
(a) Ammonotelism (i) Birds
(b) Bowman’s capsule (ii) Water reabsorption
(c) Micturition (iii) Bony fish
(d) Uricotelism (iv) Urinary bladder
(e) ADH (v) Renal tubule
Answer: The correct matching is a-iii, b-v, c-iv, d-i, e-ii
Column I | Column II |
(a) Ammonotelism | (iii) Bony fish |
(b) Bowman’s capsule | (v) Renal tubule |
(c) Micturition | (iv) Urinary bladder |
(d) Uricotelism | (i) Birds |
(e) ADH | (ii) Water reabsorption |
Q8. What is meant by the term osmoregulation?
Answer: Osmoregulation is important for the balance of water and salts in body fluids.
- It controls water and ionic content to maintain the internal environment constant.
Q9. Terrestrial animals are generally either ureotelic or uricotelic, not ammonotelic. Why?
Answer: Terrestrial animals primarily excrete urea or uric acid due to ammonia's toxicity and water requirements.
| Excretion Type | Toxicity Level | Water Needed | Example |
|---|
| Ammonotelism | High | High | Fish |
| Ureotelism | Low | Moderate | Mammals |
| Uricotelism | Very low | Minimal | Birds/Reptiles |
Q10. What is the significance of the juxta-glomerular apparatus (JGA) in kidney function?
Answer: The JGA has an important function in the control of kidney function through the monitoring of blood pressure.
- It secretes renin when GFR is low, which stimulates angiotensin II to constrict blood vessels and stimulate the secretion of aldosterone.
- This increases blood pressure and glomerular filtration rate.
Q11. Name the following:
(a) A chordate animal having flame cells as excretory structures
Answer: A chordate animal having flame cells as excretory structures is an Amphioxus.
Q11. Name the following:
(b) Cortical portions projecting between the medullary pyramids in the human kidney
Answer: Cortical portions projecting between the medullary pyramids in the human kidney are called columns of Bertin.
Q11. Name the following:
(c) A loop of capillary running parallel to Henle's loop.
Answer: A loop of capillary running parallel to Henle’s loop is the vasa recta.
Q12. Fill in the gaps :
(a) The ascending limb of Henle’s loop is _______ to water, whereas the descending limb is _______ to it.
(b) Reabsorption of water from the distal parts of the tubules is facilitated by hormone _______.
(c) Dialysis fluid contains all the constituents as in plasma except _______.
(d) A healthy adult human excretes (on average) _______ gm of urea/day.
Answer:
(a) The ascending limb of Henle’s loop is impermeable to water, whereas the descending limb is permeable to it.
(b) Reabsorption of water from the distal parts of the tubules is facilitated by the hormone ADH.
(c) Dialysis fluid contains all the constituents as in plasma except nitrogenous wastes.
(d) A healthy adult human excretes (on average) 20-30 g of urea/day.
NCERT Solutions for Class 11: Subject-wise
Important Question of NCERT Class 11 Biology Chapter 16
Take a look at this important question that can help in increasing the understanding of the concept. To score well in the exam, it is very important to practice many questions of different types. For this purpose, students can depend on the NCERT Solutions for Class 11 Biology Chapter 16 Excretory Products and Their Elimination.
Question: Which of the following is not a component of the human excretory system?
i. Kidneys
ii. Ureters
iii. Lungs
iv. Intestines
Options:
i and ii
ii and iii
i and iii
iii and iv
Answer: The correct answer is option (4).
Explanation: Lungs and intestines are not included in the excretory system and are not responsible for expelling nitrogenous wastes such as urea. The urinary system includes the kidneys, ureters, urinary bladder, and urethra, which are responsible for excretion.
