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Excretory Products and Their Elimination — NEET Biology MCQs with Solutions
Free NEET Biology Excretory Products and Their Elimination MCQs with step-by-step solutions covering Modes of Excretion, Human Excretory System & Nephron, Urine Formation, Regulation & Osmoregulation, Disorders & Other Excretory Organs. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Modes of Excretion · easy · theory
Animals that excrete nitrogenous waste mainly as ammonia are called:
A. Uricotelic
B. Guanotelic
C. Ureotelic
D. Ammonotelic ✓ Correct
Solution: Ammonotelic animals (most aquatic animals) excrete ammonia, which is highly soluble and toxic but easily diluted.
Q2 — Modes of Excretion · easy · theory
Mammals, including humans, are ______ because they mainly excrete:
A. Ureotelic; urea ✓ Correct
B. Uricotelic; urea
C. Uricotelic; uric acid
D. Ammonotelic; ammonia
Solution: Mammals convert toxic ammonia to less toxic urea (ureotelism), excreted by the kidneys.
Q3 — Human Excretory System & Nephron · easy · theory
The functional (structural) unit of the kidney is the:
A. Nephron ✓ Correct
B. Neuron
C. Alveolus
D. Glomerulus only
Solution: Each kidney has about a million nephrons — the units that form urine.
Q4 — Human Excretory System & Nephron · easy · theory
The tuft of capillaries where blood filtration begins in the nephron is the:
A. Glomerulus ✓ Correct
B. Ureter
C. Loop of Henle
D. Collecting duct
Solution: The glomerulus (enclosed by Bowman's capsule) is the site of ultrafiltration of blood.
Q5 — Urine Formation · easy · theory
The three basic processes involved in urine formation are:
A. Ingestion, digestion and egestion
B. Diffusion, osmosis and active transport
C. Glomerular filtration, reabsorption and secretion ✓ Correct
D. Filtration, digestion and absorption
Solution: Urine formation = glomerular filtration → tubular reabsorption → tubular secretion.
Q6 — Urine Formation · easy · theory
The filtration of blood at the glomerulus is called ______ because it filters everything except large proteins and cells:
A. Osmosis
B. Ultrafiltration ✓ Correct
C. Reabsorption
D. Secretion
Solution: Ultrafiltration under blood pressure passes water and small solutes into Bowman's capsule, retaining proteins/cells.
Q7 — Regulation & Osmoregulation · easy · theory
The hormone that promotes water reabsorption in the kidney (reducing urine volume) is:
A. Adrenaline
B. Thyroxine
C. Insulin
D. ADH (vasopressin) ✓ Correct
Solution: ADH (anti-diuretic hormone) increases water reabsorption from the DCT/collecting duct, concentrating urine.
Q8 — Regulation & Osmoregulation · easy · theory
When the body is dehydrated, ADH secretion ______ and urine becomes ______:
A. Stops; watery
B. Increases; more concentrated (less volume) ✓ Correct
C. Decreases; more dilute
D. Increases; more dilute
Solution: Dehydration → more ADH → more water reabsorbed → concentrated, low-volume urine.
Q9 — Disorders & Other Excretory Organs · easy · theory
The artificial process used to remove nitrogenous wastes from the blood of kidney-failure patients is:
A. Filtration by liver
B. Transfusion
C. Transpiration
D. Haemodialysis ✓ Correct
Solution: Haemodialysis uses an artificial kidney to filter urea/wastes from the blood when kidneys fail.
Q10 — Disorders & Other Excretory Organs · easy · theory
The accumulation of urea in the blood due to kidney malfunction is called:
A. Anaemia
B. Glycosuria
C. Uremia ✓ Correct
D. Diabetes
Solution: Uremia is a high blood urea level from kidney failure; it can be treated by dialysis.
Q11 — Modes of Excretion · hard · theory
Match the animal to its excretory product: Bony fish, Frog (adult), Bird —
A. Ammonia, Urea, Uric acid ✓ Correct
B. Ammonia, Uric acid, Urea
C. Uric acid, Urea, Ammonia
D. Urea, Ammonia, Uric acid
Solution: Bony fishes are ammonotelic, terrestrial adult amphibians (frogs) ureotelic, birds/reptiles uricotelic.
Q12 — Modes of Excretion · hard · theory
The conversion of ammonia to urea in mammals occurs primarily in the ______ via the ______:
A. Liver; ornithine (urea) cycle ✓ Correct
B. Liver; Calvin cycle
C. Kidney; Krebs cycle
D. Kidney; ornithine cycle
Solution: Urea is synthesised in the liver by the ornithine cycle and then carried to the kidneys for excretion.
Q13 — Human Excretory System & Nephron · hard · theory
The juxtaglomerular apparatus (JGA), important in regulating kidney function, is formed at the contact point of the:
A. Glomerulus and collecting duct
B. Ureter and bladder
C. PCT and loop of Henle
D. Afferent arteriole and the distal convoluted tubule ✓ Correct
Solution: The JGA forms where the DCT touches the afferent arteriole; it secretes renin regulating GFR and blood pressure.
Q14 — Human Excretory System & Nephron · hard · theory
The Loop of Henle plays a key role in producing ______ urine by maintaining an ______ in the medulla:
A. Concentrated; low salt medulla
B. Concentrated; osmotic (interstitial) gradient ✓ Correct
C. Dilute; equal concentration
D. Isotonic; no gradient
Solution: The counter-current mechanism of the loop of Henle and vasa recta builds a medullary gradient, enabling concentrated urine.
Q15 — Urine Formation · hard · theory
The GFR is regulated by the JGA through the renin-angiotensin mechanism: a fall in GFR causes the JG cells to release ______:
A. Insulin
B. Renin (which raises blood pressure and GFR) ✓ Correct
C. ADH
D. Aldosterone directly
Solution: Low GFR → renin release → angiotensin II → vasoconstriction + aldosterone → restores GFR/BP.
Q16 — Urine Formation · hard · theory
If about 180 L of filtrate is formed daily but only ~1.5 L of urine is voided, this shows that:
A. All filtrate becomes urine
B. The kidneys filter very little
C. No reabsorption occurs
D. Nearly 99% of the filtrate is reabsorbed by the tubules ✓ Correct
Solution: The tubules reabsorb about 99% of the filtrate (water, glucose, ions), concentrating waste into a small urine volume.
Q17 — Regulation & Osmoregulation · hard · theory
The renin-angiotensin-aldosterone system responds to a fall in blood pressure/GFR by ultimately:
A. Constricting vessels and increasing Na⁺/water reabsorption to raise blood pressure ✓ Correct
B. Increasing urine output
C. Lowering blood pressure further
D. Reducing sodium reabsorption
Solution: Renin → angiotensin II (vasoconstriction) + aldosterone (Na⁺/water retention) → restores blood pressure and GFR.
Q18 — Regulation & Osmoregulation · hard · theory
The counter-current mechanism in the medulla involves the ______ and the ______ working together:
A. Collecting duct; Bowman's capsule
B. DCT; ureter
C. PCT; glomerulus
D. Loop of Henle; vasa recta ✓ Correct
Solution: The loop of Henle (filtrate) and vasa recta (blood) run counter-current to maintain the medullary osmotic gradient.
Q19 — Disorders & Other Excretory Organs · hard · theory
Kidney stones (renal calculi) are:
A. Insoluble crystallised masses (e.g. of oxalates) formed in the kidney ✓ Correct
B. Clots of blood cells
C. Excess plasma proteins
D. Deposits of glucose
Solution: Renal calculi are hard crystalline stones (often calcium oxalate) that can obstruct the urinary tract.
Q20 — Disorders & Other Excretory Organs · hard · theory
Kidney transplantation is the ultimate treatment for acute renal failure; the donor kidney is ideally taken from:
A. A close relative to minimise immune rejection ✓ Correct
B. Any unrelated person
C. The patient's own failed kidney
D. An animal
Solution: A genetically close (matched) donor reduces the risk of immune rejection in transplantation.
Q21 — Modes of Excretion · medium · theory
Birds and reptiles are uricotelic, excreting uric acid, which is advantageous because it:
A. Is highly toxic and soluble
B. Requires very little water for excretion (conserves water) ✓ Correct
C. Cannot be stored
D. Needs a lot of water
Solution: Uric acid is nearly insoluble and can be excreted as a semi-solid paste, conserving water — useful for terrestrial/egg-laying life.
Q22 — Modes of Excretion · medium · theory
Ammonia is the most toxic nitrogenous waste and needs large amounts of water because it:
A. Requires no water
B. Is insoluble
C. Is a solid
D. Is highly soluble and must be diluted for excretion ✓ Correct
Solution: Ammonia is very soluble and toxic, so ammonotelic animals need plenty of water to flush it out.
Q23 — Human Excretory System & Nephron · medium · theory
The part of the nephron mainly responsible for the reabsorption of glucose, amino acids and most water/ions is the:
A. Collecting duct
B. Loop of Henle
C. Proximal convoluted tubule (PCT) ✓ Correct
D. Distal convoluted tubule
Solution: The PCT reabsorbs nearly all glucose and amino acids and about 70–80% of electrolytes and water.
Q24 — Human Excretory System & Nephron · medium · theory
Urine passes from the kidney to the urinary bladder through the:
A. Collecting duct only
B. Urethra
C. Nephron
D. Ureter ✓ Correct
Solution: The ureter carries urine from the kidney (renal pelvis) to the bladder; the urethra empties the bladder out.
Q25 — Urine Formation · medium · theory
The amount of filtrate formed by the kidneys per minute is the Glomerular Filtration Rate (GFR), which in a healthy adult is about:
A. 1000 mL/min
B. 500 mL/min
C. 125 mL/min ✓ Correct
D. 25 mL/min
Solution: GFR ≈ 125 mL/min (~180 L/day); most is reabsorbed, leaving ~1.5 L of urine per day.
Q26 — Urine Formation · medium · theory
Tubular secretion of H⁺, K⁺ and NH₃ into the filtrate is important for:
A. Maintaining the ionic and acid-base (pH) balance of body fluids ✓ Correct
B. Storing urine
C. Filtering blood cells
D. Reabsorbing glucose
Solution: Secretion of H⁺/K⁺/NH₃ helps maintain the pH and electrolyte balance of blood.
Q27 — Regulation & Osmoregulation · medium · theory
Aldosterone, secreted by the adrenal cortex, acts on the DCT to promote the reabsorption of:
A. Na⁺ (and water) ✓ Correct
B. Proteins
C. Urea
D. Glucose
Solution: Aldosterone increases Na⁺ (and hence water) reabsorption, raising blood volume and pressure.
Q28 — Regulation & Osmoregulation · medium · theory
The Atrial Natriuretic Factor (ANF), released when atrial walls are stretched by high blood pressure, causes:
A. Water retention
B. Vasoconstriction
C. Vasodilation and reduced blood pressure ✓ Correct
D. Increased ADH secretion
Solution: ANF counters the renin-angiotensin system: it dilates vessels and reduces blood volume/pressure.
Q29 — Disorders & Other Excretory Organs · medium · theory
The sweat and sebaceous glands of the skin assist in excretion by removing:
A. Only carbon dioxide
B. Small amounts of salts, urea, lactic acid (and sebum) ✓ Correct
C. Blood cells
D. Only glucose
Solution: Sweat glands excrete water, salts and small amounts of urea/lactate; sebaceous glands remove sterols and waxes.
Q30 — Disorders & Other Excretory Organs · medium · theory
In humans, the lungs act as accessory excretory organs by removing:
A. Bile pigments
B. Urea
C. CO₂ and some water vapour ✓ Correct
D. Uric acid
Solution: The lungs excrete large amounts of CO₂ and some water vapour with each breath.