CBSE Class 11 Biology Excretory Products and Their Elimination Assignments

Question. Assertion :- Reptiles, birds, insects excrete nitrogeneous wastes as uric acid in the from of pellet or paste.
Reason :- Uric acid, being the least toxic, can be removed with a minimum loss of water.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Many bony fishes are ammonotelic in nature.
Reason :- Ammonia, as it is readily soluble, is generally excreted by diffusion across permeable body surface or through gill surface as ammonium ions.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Nephridia are tubular excretory structure of earthworm help in osmoregulation.
Reason :- Nephridia helps to remove nitrogenous wastes and maintain a fluid and ionic balance.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- The malpighian corpuscles, PCT and DCT of nephron are situated in cortical region of kidney.
Reason :- In cortical nephrons, the loop of Henle is very long and runs deep in to medulla.
(a) A
(b) B
(c) C
(d) D
Answer: C

Question. Assertion :- On an average 1200 ml blood is filtered by kidneys per minute.
Reason :- It constitute roughly 1/5 part of the blood pumped out by each ventricle of heart in a minute.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- The JGA plays a complex regulatory role on kidney.
Reason :- A fall in glomerular blood flow can activate the JG cells to release renin.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Counter current mechanism helps to maintain a concentration gradient in the medullary interstitium.
Reason :- Interstitial gradient helps in easy passage of water from collecting tubule thereby concentrating the filtrate.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Reabsorption is maximum in ascending limb of loop of Henle.
Reason :- This region play insignificant role in maintenance of high osmolarity of medullary interstitial fluid.
(a) A
(b) B
(c) C
(d) D
Answer: D

Question. Assertion :- Substance like Glucose, amino acid, \( Na^+ \) in the glomerular filtrate are reabsorbed actively.
Reason :- Nitrogenous wastes and water in the glomerular filtrate are absorbed by passive transport.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- ANF mechanism acts as a check on the renin angiotensin mechanism.
Reason :- ANF can cause vasodilation and there by decrease blood pressure.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Other than kidneys, lungs also help in the elimination of excretory wastes.
Reason :- Our lungs remove large amount of \( CO_2 \) and significant quantities of water every day.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Analysis of urine helps in chemical diagnosis of many metabolic disorders as well as malfunctioning of kidney.
Reason :- Presence of glucose and ketone bodies in urine are indicative of diabetes mellitus
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Sebaceous glands eliminate certain substances like sterols, hydrocarbons and waxes through sebum.
Reason :- This secretion provides a protective oily covering for the skin.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- Kidney transplantation is the ultimate method in the correction of acute renal failures.
Reason :- A functioning kidney is used in transplantations from a donor, preferably a close relative
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- Stone formed within kidney called renal calculi.
Reason :- Inflammation of glomeruli of kidney called glomerulonephritis.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- "Loop of Henle" is U-shaped.
Reason :- U shape loop facilitated effective absorption of salt and water by forming counter current.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Diabetes insipidus is marked by excessive urination and too much thirst for water.
Reason :- ADH is secreted by posterior lobe of pituitary.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- Haemodialysis method is used in case of kidney failure.
Reason :- Malfunctioning kidney lead to uremia.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- A fall in GFR can activate the JG cells to release renin.
Reason :- ADH causes reabsorption of water from the distal part of the tubule.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- Human kidney can excrete highly concentrated urine than the initial filtrate.
Reason :- Human kidney make concentrated urine by medullary gradient and counter current mechanism.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- A fall in GFR can activate the JG cells to release renin.
Reason :- Ranin convert angiotensinogen to angiotensin I and II, II is powerful vasoconstrictor.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Angiotensin-II, activates the adrenal cortex to release aldosterone.
Reason :- Aldosterone causes reabsorption of \( Na^+ \) and water from the distal part of the tubule.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- When urine moves through desending limb it becomes hypertonic & as it passes through ascending limb of Henle's loop it become hypotonic.
Reason :- The descending limb is permeable to sodium ions where as ascending limb is permeable to water.
(a) A
(b) B
(c) C
(d) D
Answer: C

Question. Assertion :- The hormone aldosterone increases the absorption of \( Na^+ \) by nephron.
Reason :- To maintain pH of blood, kidney secretes \( H^+ \) ions.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- Large amount of water could be reabsorbed from collecting duct region to produce a concentrated urine.
Reason :- Collecting duct allows passage of small amounts of urea into the medullary interstitium to keep up the osmolarity.
(a) A
(b) B
(c) C
(d) D
Answer: B

Question. Assertion :- Urinary bladder is lined by transitional epithelium.
Reason :- Epithelium of urinary bladder support in expansion of bladder.
(a) A
(b) B
(c) C
(d) D
Answer: A

Question. Assertion :- Urine is light yellow coloured watery fluid with a slightly acidic pH.
Reason :- Urine contains the pigment urochrome which is a break down product of Hb from worn out RBCs.
(a) A
(b) B
(c) C
(d) D
Answer: A

Very Short Answer Questions (1 mark each)

Question 1. Which gland secrete sebum?
Answer: Sebaceous glands.
In simple words: Sebaceous glands in the skin produce sebum, an oily substance.

Exam Tip: Remember that sebaceous glands are associated with hair follicles.

Question 2. One part of loop of Henle is impermeable to water. Name it.
Answer: Ascending limb of loop of Henle.
In simple words: The ascending limb allows transport of electrolytes but does not let water pass through.

Exam Tip: Contrast this with the descending limb, which is highly permeable to water.

Question 3. Besides water, name any two contituents of human sweat.
Answer: Sodium chloride and lactic acid (glucose can also be included).
In simple words: Sweat contains small amounts of salt and metabolic wastes like lactic acid alongside water.

Exam Tip: Sweat also contains urea in minor quantities.

Question 4. Explian the function of vasa rectae.
Answer: It helps to retain reabsorbed ions and urea in the interstitial fluid of the medulla, maintaining its high osmotic pressure.
In simple words: Vasa recta act as countercurrent exchangers to preserve the concentration gradient in the kidney medulla.

Exam Tip: Mention countercurrent mechanism and medullary gradient to score full marks.

Question 5. Name two types of nephrons found in human kidney.
Answer: (i) Juxtamedullary nephron (ii) Cortical nephron.
In simple words: Nephrons are classified based on the relative position of their loops of Henle in the cortex or medulla.

Exam Tip: Juxtamedullary nephrons have long loops of Henle extending deep into the medulla.

Question 6. Define GFR (Glomerular Filtration Rate).
Answer: The amount of filtrate formed by the kidneys per minute is called Glomerular Filtration Rate (GFR).
In simple words: GFR is the volume of fluid filtered through the glomeruli into Bowman's capsule per minute, averaging 125 ml/minute in a healthy human.

Exam Tip: Normal GFR value is approximately \(125\text{ ml/minute}\) or \(180\text{ litres/day}\).

Question 7. The mechanism of concentration of filtrate is also known as counter current mechanism. Justify the statement.
Answer: It is called a countercurrent mechanism because the outflow in the ascending limb runs parallel to and in the opposite direction of the inflow in the descending limb (similarly seen in vasa recta).
In simple words: Opposing flow directions of fluid in adjacent limbs maximize the exchange of heat and solutes.

Exam Tip: Highlight the opposite flow direction between Henle's loop and vasa recta.

Question 8. What is micturition?
Answer: The process of expulsion or release of urine from the urinary bladder is called micturition.
In simple words: Micturition is urination, controlled by neural reflexes and voluntary relaxation of sphincters.

Exam Tip: Mention the CNS reflex and urinary bladder stretch receptors.

Question 9. Write the function of enzyme 'renin' produced by kidney.
Answer: Renin is used to convert angiotensinogen to angiotensin I.
In simple words: Kidney-produced renin initiates the renin-angiotensin-aldosterone system to regulate blood pressure and filtration rate.

Exam Tip: Do not confuse kidney 'Renin' (with one n) with milk-protein digesting stomach enzyme 'Rennin' (with double n).

Question 10. Name the excretory product of (i) reptiles (ii) Prawns.
Answer: (i) Reptiles: Uric acid (uricotelic)
(ii) Prawns: Ammonia (ammonotelic)
In simple words: Terrestrial reptiles excrete uric acid to conserve water, while aquatic prawns excrete soluble ammonia directly into water.

Exam Tip: Always link excretory waste type with the organism's water availability and habitat.

Short Answer Questions-II (2 marks each)

Question 11. Mark the odd ones is each of the following -
(a) Renal pelvis, medullary pyramid, renal cortex, ureter.
(b) Afferent arteriole, Henle's loop, vasa recta, efferent arteriole.
(c) Glomerular filtration, antidiuretic hormone, hypertonic urine, collecting duct.
(d) Proximal convoluted tubule, distal convoluted tubule, Henle's loop renal corpuscle.
Answer:
(a) Ureter (It is an extra-renal tube carrying urine to the urinary bladder, whereas the others are internal parts of the kidney).
(b) Henle's loop (It is part of the renal tubule, whereas the others are blood vessels associated with the glomerulus/nephron).
(c) Glomerular filtration (It is a physical filtration process, whereas the others relate to hormonal regulation and concentration of urine).
(d) Renal corpuscle (It comprises glomerulus and Bowman's capsule, while the others are tubular segments of the nephron).
In simple words: Identify the item that does not belong to the same anatomical or functional category as the others in the list.

Exam Tip: State a clear logical reason for each odd-one-out selection to ensure full marks.

Question 12. In the following diagram of longitudinal section of kidney (Fig.-1) identify and label a, b, c and d respectively.
Answer: Based on standard NCERT diagrams (Figure 19.2):
(a) Renal column / Columns of Bertini
(b) Medullary pyramid
(c) Renal vein
(d) Renal capsule
In simple words: These labels point to key internal and external structures visible in a sliced human kidney.

Question 13. In the diagram (Fig-2) showing malpighian body (renal corpuscle) identify and label p, q, r, s.
Answer: Based on standard NCERT diagrams (Figure 19.4):
p - Afferent arteriole
q - Efferent arteriole
r - Bowman's capsule
s - Proximal Convoluted Tubule (PCT)
In simple words: The Malpighian body consists of the glomerulus enclosed within Bowman's capsule, supplied by arterioles.

Exam Tip: Pay close attention to vessel widths: afferent arteriole is typically wider than the efferent arteriole.

Question 14. Name two metabolic disorders which can be diagnosed by the analysis of urine.
Answer: Glycosuria (presence of glucose) and Ketonuria (presence of ketone bodies), indicating diabetes mellitus.
In simple words: Urinalysis can detect abnormal chemical substances that signal metabolic diseases like diabetes.

Exam Tip: Mentioning Glycosuria and Ketonuria directly addresses diagnostic markers for diabetes mellitus.

Short Answer Questions-I (3 marks each)

Question 15. In the following diagram (Fig.-3) showing structure of a nephron label a, b, c d, e and f.
Answer: Based on standard NCERT diagrams of a nephron (Figure 19.3):
(a) Afferent arteriole
(b) Bowman's capsule
(c) Proximal convoluted tubule (PCT)
(d) Distal convoluted tubule (DCT)
(e) Collecting duct
(f) Loop of Henle (ascending/descending limbs and vasa recta)
In simple words: The nephron consists of a filtering corpuscle followed by a long specialized tubule divided into distinct functional zones.

Exam Tip: Labeling diagrams requires precise pointer lines touching the exact requested anatomical region.

Question 16. Describe the hormonal feed back circuit in controlling the renal functions.
Answer: Renal functions are regulated by the feedback mechanisms involving the hypothalamus, JGA (Juxtaglomerular Apparatus), and heart:
1. Osmoreceptors in the hypothalamus are activated by changes in blood volume, body fluid volume, and ionic concentration, triggering ADH (Antidiuretic Hormone) release from the neurohypophysis to facilitate water reabsorption from distal parts of the tubule.
2. A fall in glomerular blood flow/GFR activates the JGA to release renin, which converts angiotensinogen to angiotensin I and then angiotensin II, acting as a powerful vasoconstrictor and stimulating the adrenal cortex to release aldosterone (increasing sodium and water reabsorption).
3. Atrial Natriuretic Factor (ANF) is released by atrial walls in response to increased blood flow to the atria, acting as a check on the renin-angiotensin mechanism by causing vasodilation.
In simple words: Hormones like ADH, aldosterone, and ANF constantly adjust water and salt reabsorption in nephrons to maintain stable blood pressure and volume.

Exam Tip: Clearly outline the trigger, source gland, and target effect for ADH, Renin-Angiotensin, Aldosterone, and ANF.

Question 17. Give three points of difference between renin and Renin.
Answer:

In simple words: Stomach rennin digests milk protein, whereas kidney renin regulates blood pressure.

Exam Tip: Spelling matters in biology; double 'n' denotes stomach enzyme, single 'n' denotes kidney enzyme.

Question 18. What are Ammonotelic, ureotelic and Uricotelic animals.? Give on example of each type of these.
Answer:
1. Ammonotelic animals: Animals that excrete their nitrogenous waste as highly toxic ammonia. Example: Bony fishes, aquatic amphibians, and aquatic insects.
2. Ureotelic animals: Animals that excrete nitrogenous waste in the form of urea to conserve water. Example: Mammals, land-dwelling amphibians, and marine fishes.
3. Uricotelic animals: Animals that excrete nitrogenous waste as uric acid crystals or paste for maximum water conservation. Example: Reptiles, birds, and land snails.
In simple words: The type of nitrogenous waste excreted depends on water availability in the animal's habitat.

Exam Tip: Mention toxicity levels (Ammonia > Urea > Uric acid) and water requirements for each category.

Long Answer Questions (5 marks each)

Question 19. Draw a labelled diagram of human urinary system and write one function of each adrenal gland, ureter, urinary bladder kidney and urethra.
Answer:
Functions of organs:
1. Adrenal gland: Secretes hormones like aldosterone and cortisol that regulate electrolyte balance, metabolism, and blood pressure.
2. Ureter: Transports urine from the renal pelvis of the kidney to the urinary bladder via peristaltic movements.
3. Urinary bladder: Acts as a muscular temporary reservoir for storing urine until micturition occurs.
4. Kidney: Filters blood to remove metabolic wastes, regulates blood volume, electrolyte balance, and acid-base equilibrium.
5. Urethra: A muscular tube that conveys urine from the urinary bladder to the exterior of the body during urination.
In simple words: The urinary system produces, transports, stores, and eliminates liquid waste from the body while maintaining vital chemical balances.

Exam Tip: Draw a clean, well-labeled diagram showing paired kidneys, renal artery/vein, ureters, bladder, and urethra.

Question 20. Describe how urine is formed in the nephron throught filtration reabsorption and secretion.
OR
Explain the steps involved in the process of urine formation.
Answer:
Urine formation involves three main processes occurring in different parts of the nephron:
1. Glomerular Filtration: Blood enters the glomerulus through the afferent arteriole and is filtered under pressure across endothelial-epithelial membranes into Bowman's capsule. This filtration creates the glomerular filtrate (about 125 ml/min), which is protein-free plasma.
2. Tubular Reabsorption: As the filtrate flows through the renal tubules (PCT, Henle's loop, DCT), essential nutrients, water, and necessary ions are actively or passively reabsorbed back into the peritubular capillaries. For instance, PCT reabsorbs nearly all essential nutrients and 70-80% of electrolytes and water.
3. Tubular Secretion: Tubular cells secrete additional wastes (like \(\text{H}^+\), \(\text{K}^+\), and ammonia) into the filtrate to maintain ionic balance, acid-base balance, and pH of body fluids.
In simple words: Urine is produced by first filtering the blood, then reclaiming useful substances, and finally adding extra waste products into the tubule.

Exam Tip: Structure your answer clearly with the three headings: Filtration, Reabsorption, and Secretion.

Question 21. Distinguish between (i) Uricotelism and Ureotelism (ii) Sebum and sweat (iii) Proximal and distal convoluted tubules (iv) Ascending and descending limbs of Henle's loop (v) Cortical and Medullary nephrons.
Answer:
(i) Uricotelism vs Ureotelism: Uricotelism involves excreting nitrogenous waste as uric acid (very low water loss, seen in birds/reptiles), whereas ureotelism involves excreting urea (moderate water loss, seen in mammals/amphibians).
(ii) Sebum vs Sweat: Sebum is an oily, waxy secretion from sebaceous glands that lubricates skin and hair, while sweat is a watery fluid containing salts and urea secreted by sweat glands for thermoregulation.
(iii) PCT vs DCT: PCT (Proximal Convoluted Tubule) is lined by brush-bordered cuboidal epithelium for extensive reabsorption of nutrients/water, whereas DCT (Distal Convoluted Tubule) is the site for conditional reabsorption of sodium and water regulated by hormones.
(iv) Ascending vs Descending limbs: Descending limb of Henle's loop is permeable to water but impermeable to electrolytes, whereas ascending limb is impermeable to water but permeable to active transport of electrolytes.
(v) Cortical vs Medullary nephrons: Cortical nephrons have short loops of Henle barely dipping into the medulla (approx. 85%), whereas juxtamedullary nephrons have very long loops of Henle extending deep into the medullary pyramids (approx. 15%).
In simple words: Comparing these physiological and anatomical pairs highlights how kidneys and excretory structures adapt for optimal survival and homeostasis.

Exam Tip: Present distinctions in bulleted or tabular format with clear, contrasting features for each pair.

Question 22. Explain the function of different tubules of nephron.
OR
Explain the process of reabsorption and secretion of major substances at different parts of nephron with the help of schematic diagram.
Answer:
1. Proximal Convoluted Tubule (PCT): Reabsorbs all essential nutrients, 70-80% of electrolytes, and water. Maintains body pH and ionic balance by secreting \(\text{H}^+\), ammonia, and \(\text{K}^+\) into the filtrate.
2. Henle's Loop: Reabsorption is minimal in its ascending segment, but the loop plays a vital role in maintaining high osmolarity of the medullary interstitial fluid through countercurrent multiplier mechanisms.
3. Distal Convoluted Tubule (DCT): Performs conditional reabsorption of \(\text{Na}^+\) and water (under aldosterone and ADH control), reabsorbs \(\text{HCO}_3^-\), and secretes \(\text{H}^+\) and \(\text{K}^+\).
4. Collecting Duct: Extends from cortex to inner medulla. Large amounts of water are reabsorbed here to concentrate urine. It also allows passage of urea into medullary interstitium and maintains pH/ionic balance via selective ion secretion.
In simple words: Each tubular segment of the nephron has specialized transport properties to precisely adjust the composition and volume of urine.

Exam Tip: Detail the specific roles of PCT, Henle's loop, DCT, and collecting duct separately to ensure full credit.