Get Class 11 Biology Chapter 16 Excretory Products and Their Elimination Question Answer
The complete exercise and in-text answers are given below. Studying through the 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 liters 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 liters 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 Questions of NCERT Class 11 Biology Chapter 16 Excretory Products and Their Elimination
Take a look at the important questions 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 1: 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.
Question 2: Which one of the following is also known as an antidiuretic hormone?
Options:
Oxytocin
Vasopressin
Adrenaline
Calcitonin
Answer: The correct answer is option (2).
Explanation: The hypothalamus produces the peptide hormone vasopressin, sometimes referred to as antidiuretic hormone (ADH), which is secreted by the posterior pituitary gland. Its main function is to control blood pressure and the body's water balance.
Question 3: The following substances are the excretory products in animals. Choose the least toxic from among them.
Options:
Urea
Uric acid
Ammonia
Carbon dioxide
Answer: The correct answer is option (2).
Explanation:
Animals that excrete nitrogenous waste as uric acid or its salts as a paste or pellet with little water loss are known as uricotelic animals. The level of toxicity can be shown below, with ammonia being the
most toxic.
Ammonia; Urea; Uric acid
Question 4: Filtration of the blood takes place at
Options:
PCT
DCT
Collecting ducts
Malpighian body
Answer: The correct answer is option (4).
Explanation: The afferent arteriole feeds the glomerulus, a tuft of high-pressure capillaries that supply each nephron. The Bowman's capsule, a continuous, complex tubule with a proximal end that encircles the glomerulus, makes up the remainder of the nephron. The renal corpuscle, also known as the Malpighian body, is made up of the glomerulus and Bowman's capsule. The capillaries create the efferent arteriole, a second arteriole after exiting the renal corpuscle.
Question 5: The pH of human urine is approximately
Options:
6.5
7
6
7.5
Answer: The correct answer is option (3).
Explanation: The pH of human urine is approximately 6.0, making it slightly acidic under normal conditions. However, it can vary between 4.5 and 8.0 depending on factors like diet, hydration, and overall health. Acidic urine may result from a high-protein diet or metabolic acidosis, while alkaline urine can occur with vegetarian diets or urinary tract infections. Monitoring urine pH is useful in diagnosing and managing various medical conditions.
Question 6: The functional unit of the kidney is
Options:
- Nephron
- Glomerulus
- Bowman’s capsule
- Renal pelvis
Answer: The correct answer is option (1).
Explanation: A nephron is the structural and functional unit of the kidney responsible for filtration, reabsorption, secretion, and urine formation. Each human kidney contains about 1–1.5 million nephrons, which together maintain fluid balance and remove metabolic wastes from the body. The nephron includes the renal corpuscle and renal tubules, all of which work together to produce urine efficiently.
Question 7: The counter-current mechanism in the nephron mainly operates between
Options:
- PCT and DCT
- Loop of Henle and vasa recta
- Glomerulus and Bowman’s capsule
- Collecting duct and ureter
Answer: The correct answer is option (2).
Explanation: The counter-current mechanism involves the descending and ascending limbs of the Loop of Henle and the vasa recta running parallel to it. This arrangement helps create a concentration gradient in the medulla, allowing the kidneys to produce concentrated urine with minimal water loss. It is essential for water conservation, especially in mammals living in dry environments.
Question 8: Which hormone increases the reabsorption of sodium ions from the distal convoluted tubule of the nephron?
Options:
- ADH
- Aldosterone
- Thyroxine
- Insulin
Answer: The correct answer is option (2).
Explanation: Aldosterone is a mineralocorticoid hormone secreted by the adrenal cortex. It acts mainly on the distal convoluted tubule (DCT) and collecting ducts of the nephron. Aldosterone increases the reabsorption of sodium ions (Na⁺) and water into the blood while promoting the excretion of potassium ions (K⁺) into the urine. This helps regulate blood volume, blood pressure, and electrolyte balance.
Question 9: Which of the following animals is ureotelic in nature?
Options:
- Birds
- Reptiles
- Mammals
- Insects
Answer: The correct answer is option (3).
Explanation: Ureotelic animals excrete nitrogenous waste primarily in the form of urea. Mammals, including humans, convert toxic ammonia into urea in the liver through the urea cycle. Urea is less toxic than ammonia and requires a moderate amount of water for excretion, making it suitable for terrestrial animals that need to conserve water.
