Modes of Excretion — NEET Biology MCQs with Solutions
Free NEET Biology Modes of Excretion MCQs with step-by-step solutions (56 questions). Part of Excretory Products and Their Elimination. Practise online on Prepizo — no login needed.
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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 — 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.
Q4 — 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.
Q5 — 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.
Q6 — 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.
Q7 — Modes of Excretion · easy · numerical
Malpighian tubules are the principal excretory organs of:
A. Insects such as the cockroach ✓ Correct
B. Prawns and other crustaceans
C. Planaria and other flatworms
D. Earthworms and other annelids
Solution: Malpighian tubules remove nitrogenous wastes (mainly uric acid) in insects; annelids use nephridia, flatworms use protonephridia and crustaceans use antennal (green) glands.
Q8 — Modes of Excretion · easy · numerical
Flame cells (protonephridia) are the excretory structures found in:
A. The cockroach
B. The earthworm
C. The prawn
D. Planaria (flatworms) ✓ Correct
Solution: Protonephridia with flame cells carry out excretion and osmoregulation in flatworms like Planaria, rotifers and some annelid larvae.
Q9 — Modes of Excretion · easy · numerical
Antennal glands, also called green glands, are the excretory organs of:
A. Insects such as the honeybee
B. Molluscs such as Pila
C. Flatworms such as Planaria
D. Crustaceans such as the prawn ✓ Correct
Solution: Antennal (green) glands open at the base of the antennae and perform excretion in crustaceans like prawns and crayfish.
Q10 — Modes of Excretion · easy · numerical
The uricotelic mode of excretion, which conserves the most water, is shared by:
A. Bony fishes, tadpoles and prawns
B. Earthworms, leeches and Planaria
C. Reptiles, birds and insects ✓ Correct
D. Mammals, sharks and adult frogs
Solution: Reptiles, birds, land snails and insects excrete nitrogen as insoluble uric acid (paste/pellets), losing very little water.
Q11 — Modes of Excretion · medium · numerical
Match each excretory structure with the animal that possesses it: (i) Protonephridia (ii) Nephridia (iii) Malpighian tubules (iv) Antennal glands — with (p) Earthworm (q) Planaria (r) Prawn (s) Cockroach.
A. (i)-p, (ii)-q, (iii)-r, (iv)-s
B. (i)-s, (ii)-r, (iii)-q, (iv)-p
C. (i)-q, (ii)-p, (iii)-s, (iv)-r ✓ Correct
D. (i)-q, (ii)-p, (iii)-r, (iv)-s
Solution: Protonephridia occur in Planaria, nephridia in the earthworm, Malpighian tubules in the cockroach and antennal (green) glands in the prawn.
Q12 — Modes of Excretion · medium · numerical
Assertion (A): Terrestrial, egg-laying animals such as birds and reptiles are uricotelic. Reason (R): Insoluble, non-toxic uric acid can be stored in the shelled (cleidoic) egg without harming the embryo and with minimal water loss. Choose the correct option.
A. Both A and R are true but R is NOT the correct explanation of A
B. A is false but R is true
C. A is true but R is false
D. Both A and R are true and R is the correct explanation of A ✓ Correct
Solution: Uric acid is nearly insoluble and least toxic, so it can accumulate safely inside the closed egg, making uricotelism ideal for cleidoic-egg-laying terrestrial animals.
Q13 — Modes of Excretion · medium · numerical
Which of the following statements about ammonotelism is INCORRECT?
A. Ammonia is often excreted by diffusion across body surfaces such as gills
B. Ammonia is readily soluble and highly toxic, so it must be removed quickly
C. Bony fishes, aquatic amphibians and aquatic insects are largely ammonotelic
D. It is the usual mode in birds and reptiles that live on land ✓ Correct
Solution: Ammonotelism is typical of aquatic animals (bony fishes, aquatic amphibians, aquatic insects), NOT of birds and reptiles, which are uricotelic.
Q14 — Modes of Excretion · medium · numerical
The three chief nitrogenous excretory products differ in toxicity and in the water needed for their removal. Which sequence correctly arranges them in order of DECREASING water requirement for excretion?
A. Ammonia > Urea > Uric acid ✓ Correct
B. Urea > Ammonia > Uric acid
C. Uric acid > Urea > Ammonia
D. Ammonia > Uric acid > Urea
Solution: Ammonia (most toxic, highly soluble) needs the most water, urea is intermediate and uric acid (least toxic, insoluble) needs the least water.
Q15 — Modes of Excretion · medium · numerical
Some animals change their major nitrogenous waste with their environment. A frog that is ammonotelic as an aquatic tadpole typically becomes ______ as a land-dwelling adult, chiefly because ______:
A. uricotelic; uric acid is more soluble and easier to excrete on land
B. uricotelic; urea cannot be synthesised once metamorphosis is complete
C. ammonotelic still; the liver of the adult loses its urea-forming enzymes
D. ureotelic; urea is far less toxic and needs much less water than ammonia ✓ Correct
Solution: On moving to land the frog faces water scarcity, so it shifts from excreting toxic ammonia to the less toxic urea, conserving water; adult frogs are ureotelic.
Q16 — Modes of Excretion · medium · numerical
Cartilaginous marine fishes (elasmobranchs such as sharks) are best described as:
A. Uricotelic, storing uric acid to avoid any water loss
B. Ammonotelic, excreting all nitrogen instantly through the gills
C. Ureotelic, retaining urea to keep body fluids nearly iso-osmotic with sea water ✓ Correct
D. Guanotelic, excreting guanine like spiders and scorpions
Solution: Sharks are ureotelic and retain urea (and TMAO) in their blood so that their body fluids remain roughly iso-osmotic with sea water, reducing osmotic water loss.
Q17 — Modes of Excretion · easy
Least toxic nitrogenous waste is
A. Uric acid ✓ Correct
B. Urea
C. NH3
D. NH3 and urea
Solution: Uric acid is the least toxic nitrogenous waste and can be excreted with minimal loss of water.
Q18 — Modes of Excretion · medium
Which of the following is retained in small amount in kidney matrix of some animals to maintain a desired osmolarity?
A. Uric acid
B. NH3
C. NH3 and uric acid
D. Urea ✓ Correct
Solution: Urea is retained in the kidney matrix of some animals to help maintain a desired osmolarity.
Q19 — Modes of Excretion · easy
Terrestrial organisms must conserve water. The least amount of water is lost with the excretion of which nitrogenous waste product?
A. Urea
B. NH3
C. CO2
D. Uric acid ✓ Correct
Solution: Uric acid can be excreted as a semi-solid pellet, so the least amount of water is lost with its excretion.
Q20 — Modes of Excretion · medium
The less amount of water is lost with the excretion of which nitrogenous product?
A. Urea and uric acid ✓ Correct
B. NH3 and urea
C. NH3 and uric acid
D. NH3
Solution: Less water is lost with urea and uric acid compared to ammonia, which requires large amounts of water for excretion.
Q21 — Modes of Excretion · medium
Which of the following is correct about protonephridia/flame cells?
A. Protonephridia are the excretory structures in Platyhelminthes (e.g., Planaria), rotifers and some annelids
B. All of the above ✓ Correct
C. Protonephridia are primarily concerned with ionic and fluid volume regulation i.e., osmoregulation
D. Protonephridia are the excretory structures in the cephalochordates e.g., Amphioxus
Solution: Protonephridia occur in Platyhelminthes, rotifers, some annelids and cephalochordates, and are primarily concerned with ionic/osmoregulation, so all statements are correct.
Q22 — Modes of Excretion · easy
Ammonia and urea are waste products derived from the metabolic breakdown of
A. Sugars
B. Proteins ✓ Correct
C. Carbohydrates
D. Lipids
Solution: Ammonia and urea are nitrogenous wastes produced from the metabolic breakdown of proteins.
Q23 — Modes of Excretion · easy
Which of the following molecules is the most toxic to the cells?
A. Urea
B. Uric acid
C. NaCl
D. Ammonia ✓ Correct
Solution: Ammonia is the most toxic nitrogenous waste and requires large amounts of water for its elimination.
Q24 — Modes of Excretion · easy
The terms "ammonotelic", "ureotelic", and "uricotelic" are used to describe
A. Modification of kidney tubules to enhance excretion
B. The types of nitrogenous waste produced by various classes of vertebrates ✓ Correct
C. The actions of hormones on the excretory systems
D. Modes of excretory system development
Solution: Animals are classified as ammonotelic, ureotelic or uricotelic based on the type of nitrogenous waste they excrete.
Q25 — Modes of Excretion · medium
Which of the following statements is correct?
A. Ammonia is readily soluble
B. NH3 is generally excreted by the body surface or through gills (in fishes) as NH4+
C. Many bony fishes, aquatic amphibia and aquatic insects are ammoniotelic
D. All of the above ✓ Correct
Solution: All the statements about ammonotelic animals and ammonia excretion are correct.
Q26 — Modes of Excretion · medium
Which of the following statements is wrong?
A. Ureotelic animals excrete most of the nitrogenous waste as urea
B. Kidney does not play any significant role in the removal of ammonia
C. None of the above is wrong ✓ Correct
D. Ammonia and urea are the waste products derived from the metabolic breakdown of proteins
Solution: All three statements are correct, so none of them is wrong.
Q27 — Modes of Excretion · easy
Urea and uric acid are
A. More toxic than NH3
B. Non-toxic
C. Equally toxic to NH3
D. Less toxic than NH3 ✓ Correct
Solution: Urea and uric acid are less toxic than ammonia and require less water for excretion.
Q28 — Modes of Excretion · medium
Which of the following group of animals is ureotelic?
A. All of the above ✓ Correct
B. Mammals
C. Marine fishes
D. Many terrestrial amphibians
Solution: Mammals, many terrestrial amphibians and marine fishes are ureotelic, excreting nitrogenous waste mainly as urea.
Q29 — Modes of Excretion · easy
NH3 is converted into urea in
A. Kidney
B. Spleen
C. Liver ✓ Correct
D. Intestine
Solution: In ureotelic animals, ammonia is converted into urea in the liver and released into the blood, which is filtered and excreted by the kidneys.
Q30 — Modes of Excretion · medium
Which of the following groups of animals is uricotelic?
A. Insects
B. Birds and land snail
C. Reptiles
D. All of the above ✓ Correct
Solution: Reptiles, birds, land snails and insects are uricotelic, excreting nitrogenous waste as uric acid to conserve water.