Excretory Products and their Elimination (NCERT Practice Paper)

Q1. Assertion: Kidneys do not play a significant role in ammonia removal in bony fishes. Reason: Ammonia is excreted by diffusion across gill surfaces as ammonium ions.

Correct Answer: (a)
Bony fishes excrete most of their ammonia directly through the gills by diffusion, where it is rapidly washed away. The kidneys contribute only a minor amount to ammonia excretion. This diffusion mechanism is efficient in water, making the kidneys less essential for nitrogen removal.

Q2. Which of the following is correct regarding 'Other Excretory Organs'?
(i) Liver secretes bile containing bilirubin.
(ii) Sebaceous glands eliminate sterols and waxes.
(iii) Lungs remove 200 ml of CO2 per hour.

Correct Answer: (a)
The liver excretes bile pigments; sebaceous glands excrete lipids. However, lungs eliminate about 200 ml of CO₂ per minute, not per hour. So only (i) and (ii) are correct.

Q3. Match the volumes/rates:

Variable	Value
A. GFR	(I) 180 Litres/day
B. Average urine output	(II) 1 - 1.5 Litres/day
C. Urea excreted	(III) 25 - 30 gm/day

Correct Answer: (a)
GFR is about 180 L/day; urine output is 1‑1.5 L/day; urea excretion is 25‑30 g/day. These are standard physiological values.

Q4. Identify correct features of the 'Renal Pelvis':
(i) Funnel shaped space.
(ii) Located inner to hilum.
(iii) Contains projections called medullary pyramids.

Correct Answer: (a)
The renal pelvis is a funnel‑shaped structure inside the hilum. However, medullary pyramids are in the medulla, not the pelvis. So only (i) and (ii) are correct.

Q5. Match the hormones with their triggers/functions:

Hormone	Role/Trigger
A. ADH	(I) Released due to fall in GFR
B. Renin	(II) Facilitates water reabsorption
C. ANF	(III) Vasodilator (decreases BP)

Correct Answer: (a)
ADH promotes water reabsorption (anti‑diuresis); renin is released when GFR falls; ANF causes vasodilation and lowers blood pressure. These are the established roles.

Q6. Assertion: Human lungs help in excretion. Reason: They remove approximately 200ml of CO2 per minute.

Correct Answer: (a)
The lungs excrete carbon dioxide, a metabolic waste, by expelling it during expiration. About 200 ml of CO₂ is removed per minute at rest. This qualifies as an excretory function, and the reason correctly quantifies the removal.

Q7. The process of release of urine is called:

Correct Answer: (b)
Micturition is the reflex act of expelling urine from the urinary bladder. It involves the contraction of the bladder wall and relaxation of the urethral sphincter. Dialysis is an artificial process, ultrafiltration occurs in the glomerulus, and osmoregulation is the maintenance of water and salt balance.

Q8. The excretory organs in prawns are:

Correct Answer: (c)
Prawns, being crustaceans, possess antennal glands (also called green glands) located at the base of the antennae. These glands filter haemolymph and excrete nitrogenous wastes. Malpighian tubules are found in insects, nephridia in annelids, and flame cells in flatworms.

Q9. Regarding 'Podocytes', which is true?
(i) Intricate arrangement leaving slit pores.
(ii) Present in the renal tubules.
(iii) Prevent proteins from entering the lumen.

Correct Answer: (a)
Podocytes form filtration slits and prevent proteins from passing. However, they are part of Bowman's capsule, not the renal tubules. So (i) and (iii) are correct.

Q10. Which of the following is correct?
(i) ADH is also called vasopressin.
(ii) ADH can cause an increase in blood pressure.
(iii) ADH suppresses GFR.

Correct Answer: (a)
ADH is vasopressin and it raises blood pressure by vasoconstriction. However, it does not suppress GFR (it can even increase it). So only (i) and (ii) are correct.

Q11. Match the RAAS components:

Molecule	Action/Nature
A. Renin	(I) Powerful vasoconstrictor
B. Angiotensin II	(II) Stimulates Na+ reabsorption
C. Aldosterone	(III) Converts angiotensinogen

Correct Answer: (a)
Renin converts angiotensinogen to angiotensin I; angiotensin II is a potent vasoconstrictor; aldosterone promotes Na⁺ reabsorption. These are the roles in RAAS.

Q12. Match hormone source:

Hormone	Source
A. Renin	(I) Kidney (JG cells)
B. ANF	(II) Heart (Atria)
C. ADH	(III) Hypothalamus/Neurohypophysis

Correct Answer: (a)
Renin is secreted by juxtaglomerular cells of the kidney; ANF is released from the atria of the heart; ADH is produced in the hypothalamus and released from the posterior pituitary. These are their correct sources.

Q13. Match the diffusion membrane layers:

Layer	Location
A. Endothelium	(I) Glomerular blood vessels
B. Epithelium	(II) Bowman's capsule
C. Basement membrane	(III) In between the two layers

Correct Answer: (a)
The glomerular filtration barrier consists of the capillary endothelium, the basement membrane, and the epithelial layer (podocytes) of Bowman's capsule. Each layer is correctly matched.

Q14. In which type of nephron is the loop of Henle very long and runs deep into the medulla?

Correct Answer: (b)
Juxtamedullary nephrons have long loops of Henle that extend deep into the renal medulla, reaching the inner medulla. This arrangement is crucial for concentrating urine. Cortical nephrons have shorter loops that remain mostly in the cortex and are less efficient at producing concentrated urine.

Q15. Which of the following is correct for 'DCT reabsorption'?
(i) It is conditional.
(ii) Involves Na+ and water.
(iii) Capable of reabsorbing bicarbonate.

Correct Answer: (a)
DCT reabsorption is conditional (hormone‑regulated); it reabsorbs Na⁺ and water (under aldosterone and ADH) and also reabsorbs bicarbonate. All statements are correct.

Q16. Identify correct facts for 'Vasa Recta':
(i) 'U' shaped.
(ii) Parallel to Henle’s loop.
(iii) Absent or highly reduced in cortical nephrons.

Correct Answer: (a)
Vasa recta are U‑shaped, run parallel to the loop of Henle, and are reduced in cortical nephrons. All statements are correct.

Q17. Which is the most toxic form of nitrogenous waste?

Correct Answer: (c)
Ammonia is the most toxic nitrogenous waste due to its high solubility and ability to disrupt cellular pH. It requires a large volume of water to be diluted to safe levels, making it suitable only for aquatic organisms. In contrast, urea and uric acid are progressively less toxic and require less water for excretion.

Q18. Match counter current participants:

Structure	Participants
A. Henle's Loop	(I) Two limbs (Ascending/Descending)
B. Vasa Recta	(II) Two limbs (Ascending/Descending)

Correct Answer: (a)
Both the loop of Henle and the vasa recta have ascending and descending limbs, forming the counter‑current system. This anatomy is crucial for establishing the osmotic gradient.

Q19. Match the limb function in Henle's Loop:

Limb	Action
A. Descending	(I) Concentrates filtrate
B. Ascending	(II) Dilutes filtrate

Correct Answer: (a)
The descending limb concentrates filtrate by water loss; the ascending limb dilutes it by salt removal. These opposite actions establish the osmotic gradient.

Q20. Identify the correct phylum/animal based on the following statements?
(i) They are ammonotelic.
(ii) They excrete ammonia through diffusion across body surfaces.
(iii) Examples include bony fishes and aquatic amphibians.

Correct Answer: (c)
The description matches ammonotelic animals, which excrete ammonia directly and are typically aquatic. Bony fishes and aquatic amphibians are examples.

Q21. Assertion: Counter current mechanism helps in maintaining an increasing osmolarity towards the inner medulla. Reason: The gradient is mainly caused by NaCl and urea.

Correct Answer: (a)
The counter‑current multiplier system in the loop of Henle and the counter‑current exchange in vasa recta establish a medullary osmotic gradient from 300 to 1200 mOsmol L⁻¹. This gradient is primarily generated by the active transport of NaCl and the recycling of urea. The reason correctly identifies the key solutes.

Q22. Assertion: Cortical nephrons lack or have a highly reduced vasa recta. Reason: Their loop of Henle is too short and extends only very little into the medulla.

Correct Answer: (a)
Cortical nephrons have short loops of Henle that do not penetrate deep into the medulla, so the associated vasa recta are either absent or poorly developed. The reason explains the structural correlation between loop length and the presence of vasa recta.

Q23. Regarding 'Urine Formation', which statements are true?
(i) Glomerular filtration is non-selective.
(ii) Reabsorption of nutrients occurs mostly in PCT.
(iii) Tubular secretion helps in maintaining ionic balance.

Correct Answer: (b)
All three statements are correct: filtration is non‑selective based on size; nutrient reabsorption is mainly in PCT; tubular secretion adjusts ionic and pH balance.

Q24. Select the correct statements about the 'Collecting Duct':
(i) Allows passage of small amounts of urea into medullary interstitium.
(ii) Reabsorbs large amounts of water to produce concentrated urine.
(iii) Secretes H+ and K+ ions to maintain pH.

Correct Answer: (a)
The collecting duct participates in urea recycling, water reabsorption (under ADH), and secretion of H⁺ and K⁺ for acid‑base balance. All statements are correct.

Q25. Assertion: Columns of Bertini are medullary pyramids. Reason: Cortex extends in between the medullary pyramids.

Correct Answer: (a)
Columns of Bertini are extensions of the renal cortex that project between the medullary pyramids, not the pyramids themselves. The cortex does indeed extend between the pyramids. Hence the assertion is false but the reason is true.

Q26. Assertion: DCT is capable of reabsorption of HCO3-. Reason: It helps in maintaining the pH and sodium-potassium balance in blood.

Correct Answer: (a)
The DCT reabsorbs bicarbonate (HCO₃⁻) and secretes hydrogen ions, thereby regulating blood pH. It also fine‑tunes sodium and potassium levels under hormonal control. The reason correctly connects this reabsorption to acid‑base and electrolyte balance.

Q27. Assertion: Blood is filtered so finely that it is considered a process of ultra filtration. Reason: Almost all constituents of plasma except proteins pass into the lumen of Bowman's capsule.

Correct Answer: (a)
Ultrafiltration occurs because the glomerular capillary walls and the podocyte filtration slits allow passage of water, ions, and small molecules while retaining larger proteins and blood cells. This selective permeability is the basis for the term 'ultrafiltration', and the reason correctly explains the mechanism.

Q28. Assertion: Henle’s loop plays a significant role in maintaining high osmolarity of medullary interstitial fluid. Reason: The ascending limb of Henle is permeable to water.

Correct Answer: (c)
The assertion is true: the loop of Henle, via counter‑current multiplication, establishes the osmotic gradient in the medulla. However, the reason is false because the ascending limb is impermeable to water (it actively transports salts). The descending limb is water‑permeable. Hence the assertion is true but the reason is false.

Q29. Match the osmoregulation solutes:

A. Solute 1	NaCl
B. Solute 2	Urea

Correct Answer: (a)
Both NaCl and urea are the primary solutes responsible for the medullary osmotic gradient. Their roles are complementary in the counter‑current mechanism.

Q30. Identify the correct statements for 'Micturition':
(i) Bladder wall smooth muscles contract.
(ii) Urethral sphincter relaxes.
(iii) It is initiated by voluntary signals from the CNS.

Correct Answer: (a)
All statements are correct: micturition involves contraction of bladder smooth muscles, relaxation of the sphincter, and can be voluntarily initiated or inhibited via CNS control.

Q31. Match the disorders with their descriptions:

Disorder	Description
A. Uremia	(I) Crystallized salt masses
B. Renal calculi	(II) Inflammation of glomeruli
C. Glomerulonephritis	(III) Accumulation of urea in blood

Correct Answer: (a)
Uremia is urea accumulation in blood; renal calculi are kidney stones; glomerulonephritis is inflammation of glomeruli. These definitions are clinically accurate.

Q32. Stones or insoluble masses of crystallized salts (oxalates) in the kidney are:

Correct Answer: (b)
Renal calculi, commonly known as kidney stones, are hard masses formed from crystallized salts such as calcium oxalate. They can cause pain, obstruction, and infection. Glomerulonephritis is inflammation of the glomeruli, and JGA is the juxtaglomerular apparatus.

Q33. Match the kidney structures with their descriptions:

Column-I	Column-II
A. Calyces	(I) Cortical extensions into medulla
B. Renal pelvis	(II) Conical medullary masses
C. Medullary pyramids	(III) Projections from the pelvis
D. Columns of Bertini	(IV) Funnel shaped space inner to hilum

Correct Answer: (a)
Calyces are cup‑like projections from the renal pelvis; the pelvis is a funnel‑shaped space; medullary pyramids are conical masses; columns of Bertini are cortical extensions. These are standard anatomical descriptions.

Q34. The accumulation of urea in blood due to kidney malfunction is called:

Correct Answer: (b)
Uremia is the condition where urea and other nitrogenous wastes accumulate in the blood due to impaired kidney function. It is a sign of renal failure and can lead to serious complications if untreated. Treatment may involve dialysis or kidney transplantation.

Q35. Glomerulus is a tuft of capillaries formed by the:

Correct Answer: (b)
The glomerulus is a network of capillaries that arises from the afferent arteriole, a branch of the renal artery. The afferent arteriole brings blood into the glomerulus, where filtration occurs. The efferent arteriole carries blood away after filtration.

Q36. Match the permeability in Henle’s loop:

Limb	Permeability
A. Descending limb	(I) Impermeable to water, Permeable to salts
B. Ascending limb	(II) Permeable to water, Impermeable to salts

Correct Answer: (a)
The descending limb is permeable to water but impermeable to salts, while the ascending limb is impermeable to water but permeable to salts (active transport). This differential permeability is key to the counter‑current mechanism.

Q37. Identify correct features of 'Medullary osmolarity':
(i) 300 mOsmolL-1 in cortex.
(ii) 1200 mOsmolL-1 in inner medulla.
(iii) Gradient helps in water passage from collecting tubule.

Correct Answer: (a)
All statements are true: the cortex is isotonic (300 mOsmol L⁻¹), the inner medulla is hypertonic (1200), and the gradient drives water reabsorption from the collecting duct.

Q38. Match the urine characteristics:

Feature	Value
A. pH	(I) 6.0
B. Volume/day	(II) 1 - 1.5 L

Correct Answer: (a)
Normal urine pH is about 6.0 (slightly acidic) and daily volume is around 1‑1.5 litres. These are standard physiological values.

Q39. Match the substances with reabsorption mode:

Substance	Mode
A. Glucose	(I) Active
B. Amino acids	(II) Active
C. Urea	(III) Passive

Correct Answer: (a)
Glucose and amino acids are reabsorbed actively via carrier proteins; urea is reabsorbed passively by diffusion. These are the primary transport mechanisms.

Q40. Regarding 'Tubular Secretion', which is correct?
(i) Secretion of H+, K+ and ammonia.
(ii) Occurs in PCT and DCT.
(iii) Maintains pH of body fluids.

Correct Answer: (a)
Tubular secretion includes H⁺, K⁺, and ammonia; it occurs in PCT and DCT; it is essential for acid‑base balance. All statements are correct.

Q41. The functional units of the human kidney are:

Correct Answer: (b)
Nephrons are the microscopic structural and functional units of the kidney, each capable of forming urine. Each human kidney contains approximately one million nephrons. They consist of a renal corpuscle and a renal tubule, and are responsible for filtration, reabsorption, and secretion.

Q42. Match the transport mechanism in PCT:

Substance	Direction
A. Nutrients	(I) Reabsorbed into blood
B. Hydrogen ions	(II) Secreted into filtrate

Correct Answer: (a)
In the PCT, nutrients are reabsorbed into the blood, while hydrogen ions are secreted into the filtrate to maintain pH. This bidirectional transport is essential.

Q43. The process of excreting ammonia is called:

Correct Answer: (b)
Ammonotelism is the term for excreting nitrogenous waste primarily as ammonia. This mode is typical of aquatic animals such as bony fishes and amphibian larvae, where ammonia can be directly flushed out by water. The other options refer to excretion of urea (ureotelism) or uric acid (uricotelism) or the regulation of water and salt balance (osmoregulation).

Q44. Match the excretory products of different organs:

Organ	Excretory Product
A. Lungs	(I) CO2
B. Liver	(II) Sterols, Waxes
C. Sebaceous glands	(III) Bilirubin, Biliverdin

Correct Answer: (a)
Lungs excrete CO₂; liver excretes bile pigments (bilirubin, biliverdin); sebaceous glands secrete sterols and waxes. These are the respective excretory products.

Q45. Assertion: Micturition is carried out by a reflex. Reason: Stretching of the bladder wall initiates a signal to the CNS.

Correct Answer: (a)
Micturition is a spinal reflex triggered by stretch receptors in the bladder wall when it fills. The signals travel to the central nervous system (CNS), which coordinates relaxation of the urethral sphincter and contraction of the bladder. The reason explains the reflex mechanism.

Q46. Assertion: ANF acts as a check on Renin-Angiotensin mechanism. Reason: ANF causes vasodilation and decreases blood pressure.

Correct Answer: (a)
Atrial Natriuretic Factor (ANF) opposes the renin‑angiotensin system by promoting vasodilation and reducing blood pressure. It also inhibits renin secretion, directly countering the effects of angiotensin II. The reason accurately describes how ANF exerts its check.

Q47. In ureotelic animals, ammonia is converted into urea in the:

Correct Answer: (b)
The liver is the primary site for the urea cycle, where toxic ammonia is converted into the less toxic urea. This process, called the ornithine cycle, takes place in hepatocytes. The urea then enters the bloodstream and is filtered by the kidneys for excretion.

Q48. Assertion: Presence of glucose in urine is indicative of diabetes mellitus. Reason: This condition is known as Glycosuria.

Correct Answer: (b)
Both statements are true: glucose in urine (glycosuria) is a hallmark of diabetes mellitus. However, the reason merely names the condition and does not explain why it indicates diabetes (which is due to high blood glucose exceeding the renal threshold). Thus, the reason is not the correct explanation.

Q49. Correct statements about 'Renal Calculi':
(i) Stone or insoluble mass.
(ii) Formed of oxalates.
(iii) Leads to inflammation of glomeruli.

Correct Answer: (a)
Renal calculi are stones often composed of calcium oxalate; they do not inflame glomeruli (that is glomerulonephritis). Thus only (i) and (ii) are correct.

Q50. Conditional reabsorption of Na+ and water takes place in:

Correct Answer: (c)
The distal convoluted tubule (DCT) is the site of conditional reabsorption, meaning it is regulated by hormones like aldosterone and ADH. This allows fine‑tuning of sodium, potassium, and water balance based on the body's needs. In contrast, PCT reabsorption is largely constitutive.

Q51. Which nitrogenous waste can be removed with a minimum loss of water?

Correct Answer: (c)
Uric acid is the least toxic among the common nitrogenous wastes and is almost insoluble in water. It can be excreted as a semi-solid paste or pellet, thereby conserving water. This adaptation is crucial for terrestrial animals like birds and reptiles that cannot afford large water losses.

Q52. Match the specialized tissue:

Tissue Name	Location
A. JGA	(I) Modification in DCT and Afferent arteriole
B. Podocytes	(II) Inner wall of Bowman's capsule

Correct Answer: (a)
The juxtaglomerular apparatus (JGA) is formed by modified cells in the DCT and afferent arteriole; podocytes are the epithelial cells of Bowman's capsule inner layer.

Q53. Assertion: ADH prevents diuresis. Reason: ADH facilitates water reabsorption from distal parts of the tubule.

Correct Answer: (a)
ADH (antidiuretic hormone) acts on the DCT and collecting ducts to increase water reabsorption, thereby reducing urine volume (preventing diuresis). The reason directly explains the mechanism behind the anti‑diuretic effect, making it the correct explanation.

Q54. Match the animal group with its excretory product:

Column-I	Column-II
A. Bony fish	(I) Urea
B. Mammals	(II) Uric acid
C. Birds	(III) Ammonia

Correct Answer: (a)
Bony fishes are ammonotelic (excrete ammonia), mammals are ureotelic (excrete urea), and birds are uricotelic (excrete uric acid). This classification is based on the toxicity and water availability.

Q55. Which of the following describes the human kidney correctly?
(i) red-brown, bean-shaped.
(ii) 10-12 cm in length.
(iii) Average weight of 120-170 g.
(iv) Situated between T12 and L3.

Correct Answer: (b)
All statements are correct: kidneys are bean‑shaped, reddish‑brown, about 10‑12 cm long, weigh 120‑170 g each, and lie between T12 and L3 vertebrae.

Q56. Assertion: In hemodialysis, an anticoagulant like heparin is added. Reason: It prevents blood from clotting inside the dialyser unit.

Correct Answer: (a)
During hemodialysis, blood is circulated through an external dialyser, where clotting could block the circuit. Heparin is added as an anticoagulant to prevent clot formation, ensuring smooth flow through the semipermeable membrane. The reason directly explains the purpose of heparin.

Q57. Match the dialysis components:

Component	Role
A. Cellophane tube	(I) Porous membrane
B. Dialysing fluid	(II) No nitrogenous wastes
C. Heparin	(III) Anticoagulant

Correct Answer: (a)
The cellophane tube acts as a semipermeable membrane; dialysing fluid is free of nitrogenous wastes; heparin prevents clotting. These are essential for hemodialysis.

Q58. Which factor acts as a check on the renin-angiotensin mechanism by causing vasodilation?

Correct Answer: (c)
Atrial Natriuretic Factor (ANF) is released by the atria of the heart when blood volume is high. It causes vasodilation and inhibits renin secretion, counteracting the vasoconstrictor and sodium‑retaining effects of the renin‑angiotensin system, thereby lowering blood pressure.

Q59. Which of the following are correct regarding ADH?
(i) Released when osmoreceptors are activated by excessive fluid loss.
(ii) Prevents diuresis.
(iii) It is a vasodilator.

Correct Answer: (a)
ADH is released in response to increased plasma osmolarity; it promotes water reabsorption (anti‑diuresis). However, it is a vasoconstrictor, not a vasodilator. So only (i) and (ii) are correct.

Q60. Assertion: Descending limb of loop of Henle is permeable to water. Reason: Filtrate becomes more concentrated as it moves down the descending limb.

Correct Answer: (a)
The descending limb is freely permeable to water but impermeable to salts. As the filtrate descends into the hyperosmotic medulla, water leaves the tubule by osmosis, concentrating the filtrate. The reason correctly explains the consequence of water permeability.

Q61. Which hormone is released from the neurohypophysis to prevent diuresis?

Correct Answer: (d)
Antidiuretic hormone (ADH), also called vasopressin, is synthesized in the hypothalamus and released from the posterior pituitary (neurohypophysis). It increases water reabsorption in the collecting ducts, reducing urine volume (anti‑diuresis). Renin, ANF, and aldosterone are involved in other regulatory pathways.

Q62. The segment of the nephron lined by simple cuboidal brush border epithelium is:

Correct Answer: (b)
The proximal convoluted tubule (PCT) is lined by simple cuboidal epithelium with a brush border (microvilli) that greatly increases the surface area for reabsorption. The DCT has a similar epithelium but lacks brush borders; Henle's loop and collecting duct have thinner epithelia.

Q63. Regarding 'Kidney Transplantation', identify the correct statements:
(i) Ultimate method to correct acute renal failure.
(ii) Preferred donor is a close relative.
(iii) Host immune system must not reject the kidney.

Correct Answer: (a)
Transplantation is the best treatment for end‑stage renal disease; close relatives often provide better matching; immunosuppression is needed to prevent rejection. All statements are correct.

Q64. Assertion: Uric acid is excreted in the form of pellet or paste. Reason: This is a terrestrial adaptation for water conservation.

Correct Answer: (a)
Uric acid is nearly insoluble and non‑toxic, allowing it to be excreted as a semisolid paste with minimal water loss. This adaptation is vital for terrestrial animals (e.g., reptiles, birds) to conserve water. The reason correctly links the excretion mode to water conservation on land.

Q65. Which of the following is correct?
(i) Nephrons are the functional units of kidney.
(ii) Each kidney has nearly 1 million nephrons.
(iii) Medulla is divided into medullary pyramids.

Correct Answer: (a)
All statements are correct: nephrons are functional units; each kidney has ~1 million; the medulla contains medullary pyramids.

Q66. Match the process with its primary site:

Column-I (Process)	Column-II (Site)
A. Ultra filtration	(I) Collecting duct
B. Reabsorption of nutrients	(II) Glomerulus
C. Urine concentration	(III) Henle's loop and Vasa recta
D. Water reabsorption	(IV) PCT

Correct Answer: (a)
Ultrafiltration occurs at the glomerulus; nutrient reabsorption mainly in the PCT; concentration of urine involves the loop of Henle and vasa recta; final water reabsorption occurs in the collecting duct. These are the primary sites for each function.

Q67. Match the blood vessel role:

Vessel	Role
A. Afferent arteriole	(I) Brings blood to glomerulus
B. Efferent arteriole	(II) Carries blood away from glomerulus

Correct Answer: (a)
The afferent arteriole delivers blood to the glomerulus, while the efferent arteriole carries blood away after filtration. This arrangement maintains glomerular pressure.

Q68. Assertion: Mammals are ureotelic animals. Reason: They excrete nitrogenous waste as uric acid.

Correct Answer: (a)
Mammals are ureotelic, meaning their main nitrogenous waste is urea, not uric acid. Uric acid is excreted by birds and reptiles. Therefore, the assertion is true but the reason is false.

Q69. Match Column-I with Column-II based on nephron types:

Feature	Nephron Type
A. Short Henle’s loop	(I) Cortical nephron
B. Long Henle’s loop	(II) Juxta medullary nephron
C. Reduced Vasa recta	(III) Cortical nephron

Correct Answer: (a)
Cortical nephrons have short loops and reduced vasa recta; juxtamedullary nephrons have long loops and well‑developed vasa recta. The matches reflect these differences.

Q70. Assertion: Podocytes are epithelial cells of Bowman’s capsule. Reason: They are arranged to leave minute spaces called filtration slits.

Correct Answer: (a)
Podocytes are specialised epithelial cells lining the inner layer of Bowman's capsule. Their foot processes interdigitate, leaving filtration slits that allow selective passage of small molecules. This arrangement is essential for ultrafiltration, and the reason explains the functional significance.

Q71. Assertion: 99% of the glomerular filtrate is reabsorbed. Reason: Urine output is about 1.5 litres per day compared to 180 litres of filtrate.

Correct Answer: (a)
The daily filtrate volume of 180 litres and urine output of about 1.5 litres confirm that nearly 99% is reabsorbed. This massive reabsorption is essential for conserving water and solutes. The reason provides the numerical evidence that directly supports the assertion.

Q72. On average, how many grams of urea are excreted per day by an adult human?

Correct Answer: (b)
A healthy adult excretes about 25 to 30 grams of urea daily, which is the major nitrogenous waste product. This amount varies with protein intake and metabolic rate. Urea is synthesized in the liver and excreted by the kidneys.

Q73. Match the organism with its excretory structure:

Column-I	Column-II
A. Planaria	(I) Malpighian tubules
B. Earthworm	(II) Antennal glands
C. Cockroach	(III) Flame cells
D. Prawn	(IV) Nephridia

Correct Answer: (a)
Planaria (flatworm) uses flame cells (protonephridia); earthworm uses nephridia; cockroach (insect) uses Malpighian tubules; prawn (crustacean) uses antennal glands (green glands). These pairings are standard for these phyla.

Q74. Assertion: Sebaceous glands help in excretion. Reason: They eliminate substances like sterols and waxes through sebum.

Correct Answer: (a)
Sebaceous glands secrete sebum, which contains lipids including sterols and waxes. Although the primary function is lubrication, the elimination of these organic substances is a form of excretion. The reason correctly identifies the excretory products.

Q75. Match the ionic concentrations (mOsmolL-1):

Location	Concentration
A. Cortex	(I) 300
B. Inner medulla	(II) 1200

Correct Answer: (a)
The cortex has an osmolarity of about 300 mOsmol L⁻¹, while the inner medulla reaches about 1200 mOsmol L⁻¹. This gradient is essential for urine concentration.

Q76. Which are correct for 'Filtrate reabsorption'?
(i) 180 L filtrate/day vs 1.5 L urine/day.
(ii) Glucose reabsorbed actively.
(iii) Nitrogenous wastes reabsorbed passively.

Correct Answer: (a)
All statements are correct: daily filtrate is ~180 L, urine ~1.5 L; glucose is actively reabsorbed; nitrogenous wastes are passively reabsorbed.

Q77. Regarding the 'Counter Current Mechanism', which are correct?
(i) Formed by Henle's loop and vasa recta.
(ii) Osmolarity in medulla increases from 300 to 1200 mOsmolL-1.
(iii) Urea and NaCl create the gradient.

Correct Answer: (a)
All statements are correct: the counter‑current system involves the loop of Henle and vasa recta; the gradient rises from 300 to 1200 mOsmol L⁻¹; NaCl and urea are the main solutes.

Q78. Renin is released by which cells in response to a fall in GFR?

Correct Answer: (b)
Juxtaglomerular (JG) cells, which are modified smooth muscle cells in the afferent arteriole, secrete renin when they detect a drop in glomerular filtration rate or blood pressure. This initiates the renin‑angiotensin‑aldosterone system to restore GFR and blood pressure.

Q79. Assertion: The pH of human urine is slightly acidic (pH 6.0). Reason: Tubular secretion of hydrogen ions into the filtrate occurs.

Correct Answer: (a)
Urine is typically acidic (around pH 6.0) because the renal tubules secrete hydrogen ions (H⁺) into the filtrate to help maintain blood pH. This secretion acidifies the urine, and the reason correctly explains the mechanism behind the acidic pH.

Q80. Assertion: Sweat helps in excretion. Reason: It removes small amounts of urea and lactic acid.

Correct Answer: (a)
Sweat contains water, salts, and small quantities of nitrogenous wastes like urea and lactic acid. By secreting sweat, the skin acts as an accessory excretory organ. The reason correctly identifies the substances removed, explaining how sweat contributes to excretion.

Q81. Identify correct statements for 'PCT function':
(i) Reabsorbs 70-80% of electrolytes and water.
(ii) Secretes H+, K+, and Ammonia into filtrate.
(iii) Reabsorbs nearly all essential nutrients.

Correct Answer: (a)
PCT reabsorbs most water, electrolytes, and all nutrients; it also secretes H⁺, K⁺, and ammonia. Thus all statements are correct.

Q82. Which statements about 'JGA' are correct?
(i) Special sensitive region in the nephron.
(ii) Formed by modifications in DCT and afferent arteriole.
(iii) Release of renin stimulates GFR back to normal.

Correct Answer: (a)
All statements are correct: JGA is a specialized region; it involves the DCT and afferent arteriole; renin release helps restore GFR via the RAAS.

Q83. Identify the correct statements for 'Henle's Loop':
(i) Reabsorption is minimum in its ascending limb.
(ii) Descending limb is impermeable to electrolytes.
(iii) Ascending limb allows transport of electrolytes actively or passively.

Correct Answer: (b)
All statements are true: the ascending limb reabsorbs little water (minimum water reabsorption); descending is impermeable to salts; ascending transports salts actively (thick) or passively (thin).

Q84. Match the micturition components:

Component	Function
A. Stretch receptors	(I) Signal to CNS
B. Smooth muscles	(II) Contraction of bladder wall
C. Urethral sphincter	(III) Simultaneous relaxation

Correct Answer: (a)
Stretch receptors signal the CNS; smooth muscles contract the bladder; the urethral sphincter relaxes. This coordinated sequence occurs during micturition.

Q85. Which statements about 'Angiotensin II' are correct?
(i) powerful vasoconstrictor.
(ii) Activates adrenal cortex to release aldosterone.
(iii) increases glomerular blood pressure.

Correct Answer: (a)
Angiotensin II is a potent vasoconstrictor, stimulates aldosterone secretion, and raises glomerular blood pressure. All statements are correct.

Q86. Assertion: The renal cortex is characterized by medullary pyramids. Reason: Medullary pyramids project into the calyces.

Correct Answer: (d)
The assertion is false because medullary pyramids are located in the renal medulla, not the cortex. The reason is true: these pyramidal structures project into the minor calyces, which collect urine. Therefore, the correct option is that the assertion is false but the reason is true.

Q87. Assertion: Glomerulonephritis is inflammation of the kidneys. Reason: It specifically involves the inflammation of renal calyces.

Correct Answer: (a)
Glomerulonephritis is indeed an inflammation of the kidneys, but it specifically targets the glomeruli, not the calyces. The calyces are part of the collecting system. Thus the assertion is true but the reason is false.

Q88. Which statements regarding 'Hemodialysis' are true?
(i) Dialysing fluid has no nitrogenous wastes.
(ii) Cellophane tube is porous.
(iii) Blood is returned via an artery.

Correct Answer: (a)
Dialysing fluid is free of nitrogenous wastes to allow diffusion; the cellophane tube is semipermeable. However, blood is returned through a vein, not an artery. So (i) and (ii) are correct.

Q89. The notch through which ureters, blood vessels, and nerves enter the kidney is called:

Correct Answer: (c)
The hilum is a concave notch on the medial surface of the kidney where the renal artery, renal vein, ureter, lymphatic vessels, and nerves enter or exit. The renal pelvis is the funnel-shaped space inside, calyces are cup-like extensions, and the cortex is the outer region of the kidney.

Q90. Protonephridia (flame cells) are the excretory structures in:

Correct Answer: (c)
Flame cells, also known as protonephridia, are characteristic of flatworms (Platyhelminthes) like Planaria. They function in osmoregulation and excretion by filtering body fluids through ciliated cells. Earthworms have nephridia, cockroaches have Malpighian tubules, and prawns have antennal glands.

Q91. Assertion: Ammonia requires a large amount of water for its elimination. Reason: Ammonia is the most toxic form of nitrogenous waste.

Correct Answer: (a)
Ammonia's high toxicity means it must be diluted to safe concentrations, demanding substantial water. This is why ammonotelic animals are typically aquatic and excrete ammonia directly into water. The toxicity directly explains the need for large water volumes, so the reason correctly justifies the assertion.

Q92. The 'U' shaped capillary vessel running parallel to the Henle’s loop is:

Correct Answer: (b)
The vasa recta is a hairpin‑shaped capillary network that runs alongside the loop of Henle, forming an essential part of the counter‑current mechanism. It helps maintain the osmotic gradient in the renal medulla. Peritubular capillaries surround the convoluted tubules, while the glomerulus is the filtering capillary tuft.

Q93. Malpighian body (renal corpuscle) consists of:

Correct Answer: (b)
The Malpighian body, also called the renal corpuscle, is formed by the glomerulus (a tuft of capillaries) enclosed within Bowman's capsule. This is the site of ultrafiltration. The PCT (proximal convoluted tubule) and DCT (distal convoluted tubule) are parts of the renal tubule that follow the corpuscle.

Q94. What percentage of the filtrate is reabsorbed by the renal tubules?

Correct Answer: (d)
About 99% of the glomerular filtrate is reabsorbed back into the blood, leaving only about 1% (around 1.5 litres) as urine. This massive reabsorption is vital for conserving water, electrolytes, and nutrients while excreting wastes.

Q95. Assertion: Angiotensin II is a powerful vasoconstrictor. Reason: It increases glomerular blood pressure and GFR.

Correct Answer: (a)
Angiotensin II constricts arterioles, raising systemic and glomerular blood pressure. This increased pressure in the glomerulus elevates the glomerular filtration rate (GFR). The reason correctly explains the consequence of vasoconstriction, making it a valid explanation.

Q96. The human kidneys are situated between the levels of:

Correct Answer: (b)
The paired kidneys are retroperitoneal organs located at the level of the last thoracic (T12) to the third lumbar (L3) vertebrae. The right kidney is slightly lower due to the presence of the liver. This anatomical position is consistent across most individuals.

Q97. Select correct statements for 'Ultra Filtration barriers':
(i) Endothelium of glomerular vessels.
(ii) Epithelium of Bowman’s capsule.
(iii) Basement membrane.

Correct Answer: (a)
The glomerular filtration barrier consists of three layers: capillary endothelium, basement membrane, and epithelial podocytes of Bowman's capsule. All are correct.

Q98. The average Glomerular Filtration Rate (GFR) in a healthy individual is:

Correct Answer: (b)
The GFR is approximately 125 ml per minute (about 180 litres per day). This high rate ensures that the blood is thoroughly filtered, and most of the filtrate is reabsorbed later. Deviations from this value can indicate kidney dysfunction.

Q99. Match the nephron parts with their locations/features:

Column-I	Column-II
A. Malpighian corpuscle	(I) Brush border epithelium
B. PCT	(II) Hairpin shape
C. Henle’s loop	(III) Found only in cortex

Correct Answer: (a)
The Malpighian corpuscle (glomerulus + Bowman's capsule) is located in the cortex; the PCT has a brush border; Henle's loop has a hairpin shape. These features are characteristic of each nephron segment.

Q100. Glycosuria and Ketonuria in urine are indicative of:

Correct Answer: (b)
The presence of glucose (glycosuria) and ketone bodies (ketonuria) in urine is a classic sign of diabetes mellitus, particularly when blood sugar levels are elevated. In diabetes, the renal threshold for glucose is exceeded, leading to its appearance in urine along with ketones due to fat metabolism.