NEET Biology · NCERT Class 11 · Chapter 4
Animal Kingdom: 30 free questions from the Class 11 bank
The biggest chapter in Class 11, and the one most often answered from memory of a classroom chart instead of the NCERT text. Symmetry, coelom, segmentation and the notochord decide the answer far more often than the animal's name does.
Where the marks go
What NEET actually asks in Animal Kingdom
- Coelom, correctlyAcoelomate, pseudocoelomate and coelomate, each with the phylum that belongs in it. The roundworms' pseudocoelom is the usual trap.
- Characters that name a phylumWater vascular system, flame cells, malpighian tubules, nephridia, choanocytes. Each belongs to exactly one phylum, and the exam relies on you blurring them.
- Chordate is not vertebrateNotochord, dorsal hollow nerve cord, pharyngeal gill slits. Protochordates have all three and are still not vertebrates.
Free questions
30 solved MCQs, answer marked and reasoning written out
Every question below is free to read — no sign-up, no email. 4 of them are real questions from past NEET papers. The other 269 questions in this chapter are in the book and in practice access.
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Q1 Multi-statement analysis
Cyclostomata: (i) cartilaginous cranium and vertebral column (ii) closed circulation (iii) migrate to fresh water for spawning (iv) do not die after spawning. How many are correct?
- 1.One
- 2.Two
- 3.ThreeCorrect answer
- 4.Four
Why option 3 is the answer
The trap: (i)–(iii) correct; they die within a few days after spawning, so (iv) is wrong.
What this is testing: Cyclostomata's skeleton, circulation and post-spawning fate.
Cyclostomes have a cartilaginous cranium and vertebral column, a closed circulatory system, and migrate to fresh water to spawn. (i)-(iii) are correct.
(iv) is the trap. Cyclostomes DO die within a few days after spawning — the statement reverses this into "do not die", when dying soon after breeding is in fact a defining part of their life cycle.
So three statements are correct.
Cyclostomes spawn once in fresh water and die afterwards. Migration and death are two halves of the same life history.
NCERT Class 11 Biology, page 47
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Q2 Multi-statement analysis
Coelenterate digestion and cavity: (i) a central gastro-vascular cavity is present (ii) a single opening (mouth) lies on the hypostome (iii) digestion is extracellular and intracellular (iv) digestion is only intracellular. How many are correct?
- 1.One
- 2.Two
- 3.ThreeCorrect answer
- 4.Four
Why option 3 is the answer
The trap: (i)–(iii) correct; digestion is both extra- and intracellular, so (iv) is wrong.
What this is testing: the coelenterate gut, with the mode of digestion as the trap.
Coelenterates have a central gastro-vascular cavity, a single mouth opening located on a raised hypostome, and digestion that is both extracellular and intracellular. (i)-(iii) are correct.
(iv) is the trap and contradicts (iii) directly. Digestion is NOT only intracellular in coelenterates — food is first broken down extracellularly in the gastro-vascular cavity before cells take up particles for intracellular digestion.
So three statements are correct.
One cavity, one opening, and digestion both inside and outside the cells. Coelenterates do it both ways because they have no true gut.
NCERT Class 11 Biology, page 41
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Q3 Multi-statement analysis
Porifera: (i) choanocytes line the spongocoel and canals (ii) digestion is intracellular (iii) skeleton of spicules or spongin fibres (iv) sexes are separate. How many are correct?
- 1.One
- 2.Two
- 3.ThreeCorrect answer
- 4.Four
Why option 3 is the answer
The trap: (i)–(iii) correct; sponges are hermaphrodite, so (iv) is wrong.
What this is testing: Porifera anatomy and reproduction, with sexuality as the closing trap.
In sponges, choanocytes line the spongocoel and canals, digestion is intracellular, and the skeleton is made of spicules or spongin fibres. (i)-(iii) are correct.
(iv) is the trap. Sponges are hermaphrodite (bisexual), not sexes-separate — a single individual produces both types of gametes, unlike the dioecious pattern this statement describes.
So three statements are correct.
Choanocytes, intracellular digestion, spicules. Sponges are hermaphrodite, so separate sexes is the false statement.
NCERT Class 11 Biology, page 40
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Q4 Multi-statement analysis
Chondrichthyes reproduction: (i) males bear claspers on the pelvic fins (ii) internal fertilisation (iii) many are viviparous (iv) all are oviparous. How many are correct?
- 1.One
- 2.Two
- 3.ThreeCorrect answer
- 4.Four
Why option 3 is the answer
The trap: (i)–(iii) correct; many are viviparous, so 'all oviparous' (iv) is wrong.
What this is testing: Chondrichthyes reproduction, ending on an oviparity trap.
Male cartilaginous fishes bear claspers on their pelvic fins, fertilisation is internal, and many species are viviparous, giving birth to live young. (i)-(iii) are correct.
(iv) is the trap and contradicts (iii). Many chondrichthyans are viviparous, so "all are oviparous" is false — the class shows a mix of reproductive modes, not a single one.
So three statements are correct.
Claspers, internal fertilisation, many viviparous. Cartilaginous fishes breed far more like reptiles than like bony fishes.
NCERT Class 11 Biology, page 48
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Q5 Multi-statement analysis
The sponge canal system helps in: (i) food gathering (ii) respiratory exchange (iii) removal of waste (iv) locomotion. How many are correct?
- 1.One
- 2.Two
- 3.ThreeCorrect answer
- 4.Four
Why option 3 is the answer
The trap: (i)–(iii) correct; the canal system is not a locomotory device, so (iv) is wrong.
What this is testing: what the sponge canal system actually does, with locomotion as the trap.
The water current through a sponge's canal system brings in food particles, allows respiratory gas exchange, and carries away waste. (i)-(iii) are correct.
(iv) is the trap. The canal system is not a locomotory device — sponges are largely sessile (fixed in place) as adults, so movement is not among its functions.
So three statements are correct.
One water current does the feeding, the breathing and the waste disposal. A sponge cannot move, so it moves the water instead.
NCERT Class 11 Biology, page 40
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Q6 Multi-statement analysis
The notochord is: (i) mesodermally derived (ii) rod-like (iii) formed on the dorsal side (iv) formed during embryonic development. How many are correct?
- 1.One
- 2.Two
- 3.Three
- 4.FourCorrect answer
Why option 4 is the answer
The trap: All four are correct.
What this is testing: plain recall of what the notochord is and how it forms.
The notochord is mesodermally derived, rod-like in shape, formed on the dorsal side of the body, and appears during embryonic development in all chordates, at least at some stage.
All four statements describe the same structure consistently, with nothing reversed or borrowed from elsewhere, so this is a straight recall question with no trap to find.
So all four statements are correct.
Mesodermal, rod-like, dorsal, embryonic. Four properties, and the phylum takes its name from this one structure.
NCERT Class 11 Biology, page 39
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Q7 Multi-statement analysis
Aschelminthes: (i) roundworms, circular in cross-section (ii) pseudocoelomate (iii) complete alimentary canal with a muscular pharynx (iv) sexes are not separate. How many are correct?
- 1.One
- 2.Two
- 3.ThreeCorrect answer
- 4.Four
Why option 3 is the answer
The trap: (i)–(iii) correct; aschelminthes are dioecious, so (iv) is wrong.
What this is testing: Aschelminthes (roundworm) features, ending on a sexuality trap.
Aschelminthes are roundworms, circular in cross-section, pseudocoelomate, and have a complete alimentary canal with a muscular pharynx. (i)-(iii) are correct.
(iv) is the trap. Aschelminthes ARE dioecious, with sexes separate — the statement wrongly claims sexes are not separate, reversing a true fact about this phylum.
So three statements are correct.
Roundworms are dioecious, and the females are usually longer. Separate sexes set them apart from the hermaphrodite flatworms.
NCERT Class 11 Biology, page 43
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Q8 Multi-statement analysis
Porifera: (i) generally marine (ii) mostly asymmetrical (iii) cellular level of organisation (iv) water enters through the osculum and leaves through the ostia. How many are correct?
- 1.One
- 2.Two
- 3.ThreeCorrect answer
- 4.Four
Why option 3 is the answer
The trap: (i)–(iii) correct; water enters through the ostia and leaves through the osculum, so (iv) is wrong.
What this is testing: Porifera's habitat and symmetry, with the water-current direction as the closing trap.
Sponges are generally marine, mostly asymmetrical in shape, and show the cellular level of organisation. (i)-(iii) are correct.
(iv) is the trap. Water enters a sponge through the ostia (pores) and leaves through the osculum — the statement reverses this flow, which is the single most tested fact about the sponge body plan.
So three statements are correct.
Water in through the ostia, out through the osculum. One big opening out, many small ones in - and the question reverses them.
NCERT Class 11 Biology, page 40
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Q9 Assertion and Reason
AssertionAschelminthes are pseudocoelomate.
ReasonIn aschelminthes the sexes are separate and the females are often longer than the males.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of ACorrect answer
- 3.A is true but R is false
- 4.A is false but R is true
Why option 2 is the answer
The trap: Both are true; the reproductive fact is a parallel feature and does not explain the pseudocoelom.
What this is testing: whether reproductive details explain the pseudocoelom in aschelminthes.
A says aschelminthes are pseudocoelomate. True. R says in aschelminthes sexes are separate and females are often longer than males. Also true, but this is a fact about reproduction, unrelated to how the body cavity is lined.
Both are true but R does not explain A, giving (2). A pseudocoelom is defined by scattered mesodermal pouches, not by sexual dimorphism in body length.
NCERT Class 11 Biology, page 43
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Q10 Assertion and Reason
AssertionIn chordates the central nervous system is ventral, solid and double.
ReasonIn chordates the nerve cord is dorsal, hollow and single.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of A
- 3.A is true but R is false
- 4.A is false but R is trueCorrect answer
Why option 4 is the answer
The trap: A is false (that describes non-chordates); R is true.
What this is testing: the true position and shape of the chordate nerve cord.
A says in chordates the CNS is ventral, solid and double. False — that describes NON-chordates. In chordates the nerve cord is dorsal, hollow and single, which is exactly what R states, and R is true.
A is false but R is true, giving (4). The trap swaps the chordate and non-chordate nerve-cord descriptions in the assertion while leaving the reason correct.
NCERT Class 11 Biology, page 46
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Q11 Assertion and Reason
AssertionCnidarians show the tissue level of organisation.
ReasonCnidarians are diploblastic, with a mesoglea between the ectoderm and endoderm.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of ACorrect answer
- 3.A is true but R is false
- 4.A is false but R is true
Why option 2 is the answer
The trap: Both are true; the germ-layer arrangement is a parallel structural fact and does not explain the tissue-level organisation.
What this is testing: whether the diploblastic body plan explains the cnidarian tissue level.
A says cnidarians show the tissue level of organisation. True. R says cnidarians are diploblastic, with a mesoglea between the ectoderm and endoderm. Also true, but this describes the number of germ layers, a separate structural fact that runs alongside the tissue-level claim rather than explaining it.
Both are true but R does not explain A, giving (2).
Two germ layers and tissue-level organisation are separate descriptions. One counts layers, the other ranks complexity.
NCERT Class 11 Biology, page 41
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Q12 Assertion and Reason
AssertionNereis, the earthworm and the leech are all monoecious.
ReasonNereis is dioecious, whereas the earthworm and the leech are monoecious.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of A
- 3.A is true but R is false
- 4.A is false but R is trueCorrect answer
Why option 4 is the answer
The trap: A is false; R is true.
What this is testing: which annelid genus is dioecious and which are monoecious.
A says Nereis, the earthworm and the leech are ALL monoecious. False — Nereis is dioecious (sexes separate), while the earthworm and the leech are monoecious. R states exactly this correct split, and R is true.
A is false but R is true, giving (4). The trap lumps all three annelid examples into one reproductive pattern when the textbook separates them.
NCERT Class 11 Biology, page 43
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Q13 Assertion and Reason
AssertionArthropods excrete by means of malpighian tubules.
ReasonArthropods have an open circulatory system in which the blood bathes the tissues.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of ACorrect answer
- 3.A is true but R is false
- 4.A is false but R is true
Why option 2 is the answer
The trap: Both are true parallel arthropod features; the circulatory type does not explain the excretory structure.
What this is testing: whether an open circulatory system explains malpighian tubule excretion in arthropods.
A says arthropods excrete by means of malpighian tubules. True. R says arthropods have an open circulatory system in which blood bathes the tissues. Also true, but this is a separate circulatory fact — it does not explain why excretion happens through malpighian tubules specifically.
Both are true but R does not explain A, giving (2).
Excretory organ and circulatory plan are two independent features. Both true of arthropods, neither causing the other.
NCERT Class 11 Biology, page 44
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Q14 Assertion and Reason
AssertionMolluscs have a distinct muscular foot and visceral hump.
ReasonThe molluscan mantle encloses a mantle cavity that houses the gills.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of ACorrect answer
- 3.A is true but R is false
- 4.A is false but R is true
Why option 2 is the answer
The trap: Both are true parallel features of the molluscan body plan; one does not cause the other.
What this is testing: whether the mantle cavity explains the molluscan foot and visceral hump.
A says molluscs have a distinct muscular foot and visceral hump. True. R says the molluscan mantle encloses a mantle cavity that houses the gills. Also true, but this describes a different part of the body plan — the mantle cavity does not cause or explain the foot and hump.
Both are true but R does not explain A, giving (2).
Foot and hump are one part of the plan, mantle and cavity another. Describing a neighbour is not explaining a feature.
NCERT Class 11 Biology, page 44
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Q15 Assertion and Reason
AssertionThe medusa of a cnidarian is a sessile, cylindrical body form.
ReasonThe medusa is an umbrella-shaped, free-swimming body form.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of A
- 3.A is true but R is false
- 4.A is false but R is trueCorrect answer
Why option 4 is the answer
The trap: A is false (that describes the polyp); R is true.
What this is testing: which body form, polyp or medusa, is sessile and which is free-swimming.
A says the medusa is a sessile, cylindrical body form. False — that description fits the POLYP; the medusa is umbrella-shaped and free-swimming, exactly as R states, and R is true.
A is false but R is true, giving (4). The trap swaps the two coelenterate body forms' descriptions.
Polyp sessile and cylindrical, medusa free-swimming and umbrella-shaped. The two forms alternate, and the descriptions are easily swapped.
NCERT Class 11 Biology, page 41
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Q16 Assertion and Reason
AssertionEchinoderm larvae are radially symmetrical while the adults are bilateral.
ReasonEchinoderm larvae are bilaterally symmetrical while the adults are radially symmetrical.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of A
- 3.A is true but R is false
- 4.A is false but R is trueCorrect answer
Why option 4 is the answer
The trap: A is false (the condition is reversed); R is true.
What this is testing: which life stage of echinoderms is radial and which is bilateral.
A says echinoderm larvae are radially symmetrical while the adults are bilateral. False — this is exactly reversed: larvae are bilaterally symmetrical while adults are radially symmetrical, which is what R correctly states.
A is false but R is true, giving (4). The trap swaps larval and adult symmetry.
Bilateral larva, radial adult - and that order is the evidence of bilateral ancestry. Reversing it removes the whole significance.
NCERT Class 11 Biology, page 45
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Q17 Assertion and Reason
AssertionCtenophores are exclusively marine.
ReasonBioluminescence is well-marked in ctenophores.
- 1.Both A and R are true and R is the correct explanation of A
- 2.Both A and R are true but R is not the correct explanation of ACorrect answer
- 3.A is true but R is false
- 4.A is false but R is true
Why option 2 is the answer
The trap: Both are true ctenophore features; bioluminescence is a parallel property and does not explain the marine habitat.
What this is testing: whether bioluminescence explains a ctenophore's marine habitat.
A says ctenophores are exclusively marine. True. R says bioluminescence is well-marked in ctenophores. Also true, but it is an unrelated property of these animals and does not explain why they live only in the sea.
Both are true but R does not explain A, giving (2).
Glowing and living in the sea are unrelated properties. Plenty of marine animals do not glow, and the reason explains nothing.
NCERT Class 11 Biology, page 42
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Q18 Statement I and Statement II
Statement IMammals possess mammary glands and hair.
Statement IIAll mammals are viviparous.
- 1.Both Statement I and Statement II are correct
- 2.Both Statement I and Statement II are incorrect
- 3.Statement I is correct but Statement II is incorrectCorrect answer
- 4.Statement I is incorrect but Statement II is correct
Why option 3 is the answer
The trap: I correct; the platypus is oviparous, so II is incorrect.
What this is testing: mammalian defining features and the reproductive exception together.
Statement I: mammals possess mammary glands and hair. Correct. Statement II: all mammals are viviparous. Incorrect — the platypus is a named exception that is oviparous, laying eggs instead of giving birth to live young.
So (3): I correct, II incorrect. The trap turns "most" mammals into "all" mammals, erasing the textbook exception.
Platypus and echidna lay eggs and still have mammary glands. The word 'all' is what makes the second statement fail.
NCERT Class 11 Biology, page 51
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Q19 Statement I and Statement II
Statement IThe amphibian heart is three-chambered.
Statement IIThe avian heart is four-chambered.
- 1.Both Statement I and Statement II are correctCorrect answer
- 2.Both Statement I and Statement II are incorrect
- 3.Statement I is correct but Statement II is incorrect
- 4.Statement I is incorrect but Statement II is correct
Why option 1 is the answer
The trap: Both statements are correct.
What this is testing: heart chamber number across two classes, amphibians and birds.
Statement I: the amphibian heart is three-chambered. Correct. Statement II: the avian heart is four-chambered. Correct — birds fully separate oxygenated and deoxygenated blood to meet their high metabolic demand.
Both are correct, so the answer is (1). This pairing tests whether you can hold two different classes' heart structures straight at the same time, without either fact interfering with the other.
NCERT Class 11 Biology, page 48
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Q20 Statement I and Statement II
Statement IAdult echinoderms are radially symmetrical.
Statement IIEchinoderm larvae are radially symmetrical.
- 1.Both Statement I and Statement II are correct
- 2.Both Statement I and Statement II are incorrect
- 3.Statement I is correct but Statement II is incorrectCorrect answer
- 4.Statement I is incorrect but Statement II is correct
Why option 3 is the answer
The trap: I correct; the larvae are bilaterally symmetrical, so II is incorrect.
What this is testing: adult versus larval symmetry in echinoderms.
Statement I: adult echinoderms are radially symmetrical. Correct. Statement II: echinoderm larvae are radially symmetrical. Incorrect — echinoderm larvae are BILATERALLY symmetrical, evidence of the group's bilateral ancestry that gets lost by adulthood.
So (3): I correct, II incorrect. The trap assumes the adult's symmetry must carry back to the larval stage.
Radial adult, bilateral larva. The larva preserves the ancestry that the adult conceals.
NCERT Class 11 Biology, page 45
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Q21 Match the columns
Match the chordate group with its feature:
Column I Column II (a) Urochordata (iv) jawless ectoparasite (b) Cephalochordata (ii) cartilaginous, marine (c) Cyclostomata (i) notochord in larval tail only (d) Chondrichthyes (iii) notochord head to tail, persistent - 1.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
- 2.(a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)Correct answer
- 3.(a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)
- 4.(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
Why option 2 is the answer
The trap: Urochordata-larval-tail notochord, Cephalochordata-persistent notochord, Cyclostomata-jawless ectoparasite, Chondrichthyes-cartilaginous marine.
What this is testing: matching chordate groups to their defining feature.
Urochordata keeps its notochord only in the larval tail, Cephalochordata keeps it head to tail for life, Cyclostomata is a jawless ectoparasite, and Chondrichthyes is cartilaginous and marine. That gives (a)-(i), (b)-(iii), (c)-(iv), (d)-(ii), option 2, a straight match.
Option 1 swaps Urochordata and Cephalochordata, giving the persistent notochord to Urochordata instead of Cephalochordata — exactly reversed from the true pattern.
NCERT Class 11 Biology, page 46
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Q22 Match the columns
Match the Table 4.1 chordate character with its state:
Column I Column II (a) Notochord (iii) pharynx perforated (b) Nerve cord (iv) ventral (c) Gill slits (i) present (d) Heart (ii) dorsal, hollow, single - 1.(a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
- 2.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)Correct answer
- 3.(a)-(i), (b)-(iii), (c)-(ii), (d)-(iv)
- 4.(a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
Why option 2 is the answer
The trap: Notochord-present, Nerve cord-dorsal/hollow/single, Gill slits-pharynx perforated, Heart-ventral.
What this is testing: matching the four core chordate characters (Table 4.1) to their described state.
The notochord is present, the nerve cord is dorsal, hollow and single, the gill slits mean a perforated pharynx, and the heart is ventral. That gives (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv), option 2, a straight, unshuffled match of the table.
Option 4 reverses the whole list, pairing the notochord's "present" state with the heart row and the heart's "ventral" state with the notochord row. Read each character against its own row.
NCERT Class 11 Biology, page 46
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Q23 Match the columns
Match the insect/arthropod with its role:
Column I Column II (a) Apis (i) lac insect (b) Bombyx (ii) living fossil (c) Laccifer (iii) honey bee (d) Limulus (iv) silkworm - 1.(a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
- 2.(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
- 3.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)Correct answer
- 4.(a)-(i), (b)-(iv), (c)-(iii), (d)-(ii)
Why option 3 is the answer
The trap: Apis-honey bee, Bombyx-silkworm, Laccifer-lac insect, Limulus-living fossil.
What this is testing: matching an insect or arthropod genus to its common role.
Apis is the honey bee, Bombyx is the silkworm, Laccifer is the lac insect, and Limulus (the king crab) is called a living fossil. That gives (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii), option 3, a straight match.
Option 1 swaps Apis and Bombyx, giving the honey bee the "silkworm" label. Both are economically important insects covered together in the textbook, which is exactly why the paper pairs them for a swap.
NCERT Class 11 Biology, page 44
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Q24 Match the columns
Match the phylum with its distinctive feature (Table 4.2):
Column I Column II (a) Porifera (i) comb plates (b) Ctenophora (ii) pores and canals in the wall (c) Echinodermata (iii) jointed appendages (d) Arthropoda (iv) water vascular system - 1.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
- 2.(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
- 3.(a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
- 4.(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)Correct answer
Why option 4 is the answer
The trap: Porifera-pores/canals, Ctenophora-comb plates, Echinodermata-water vascular system, Arthropoda-jointed appendages.
What this is testing: matching each phylum to its one distinctive diagnostic feature.
Porifera is defined by pores and canals in its body wall, Ctenophora by comb plates, Echinodermata by the water vascular system, and Arthropoda by jointed appendages. That gives (a)-(ii), (b)-(i), (c)-(iv), (d)-(iii), option 4, a straight match with nothing shuffled.
Option 3 swaps Echinodermata and Arthropoda, giving the water vascular system to Arthropoda and jointed appendages to Echinodermata — exactly reversed from their true diagnostic features.
NCERT Class 11 Biology, page 51
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Q25 Exception / incorrect
Identify the INCORRECT pair (class – heart):
- 1.Chondrichthyes – two-chambered
- 2.Amphibia – three-chambered
- 3.Reptilia – four-chambered in allCorrect answer
- 4.Aves – four-chambered
Why option 3 is the answer
The trap: Reptiles are usually three-chambered; four-chambered only in crocodiles.
What this is testing: recognising the one class-heart pairing that is wrong.
Chondrichthyes-two-chambered, Amphibia-three-chambered, and Aves-four-chambered are all correct. Reptilia-"four-chambered in all" is the exception — most reptiles have a THREE-chambered heart, with a four-chambered heart only in crocodiles, the one named exception.
The trap: this option takes the crocodile's special case and wrongly generalises it to the whole class. So this pair is the answer.
NCERT Class 11 Biology, page 49
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Q26 Sequence / ordering
Arrange these vertebrate classes by increasing heart-chamber number:
- 1.Aves → Amphibia → Chondrichthyes
- 2.Chondrichthyes → Amphibia → AvesCorrect answer
- 3.Amphibia → Chondrichthyes → Aves
- 4.Chondrichthyes → Aves → Amphibia
Why option 2 is the answer
The trap: Chondrichthyes (two) → Amphibia (three) → Aves (four).
What this is testing: ordering vertebrate classes by their number of heart chambers, a second time with different classes.
Chondrichthyes has a two-chambered heart, Amphibia a three-chambered heart, and Aves a four-chambered heart, so the increasing order is Chondrichthyes → Amphibia → Aves, giving option 2.
Option 1 starts with Aves (four chambers) and ends with Chondrichthyes (two chambers), running the numeric sequence backwards. Anchor each class to its chamber count directly rather than to any assumed order of "simple to complex" animals.
NCERT Class 11 Biology, page 48
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Q27 NEET 2026 (Cancelled)
AssertionAll vertebrates are chordates, but all chordates are not vertebrates.
ReasonThe members of subphylum Vertebrata possess a notochord during the embryonic period; the notochord is replaced by a cartilaginous or bony vertebral column in adults.
- 1.Both A and R are true and R is the correct explanation of ACorrect answer
- 2.Both A and R are true but R is not the correct explanation of A
- 3.A is true but R is false
- 4.A is false but R is true
Why option 1 is the answer
The trap: R correctly explains why vertebrates are a subset of chordates — they pass through a notochord stage before it is replaced by the vertebral column.
What this is testing: whether a stated reason genuinely explains why vertebrates form a subset of chordates.
Assertion is true: every vertebrate is a chordate, but not every chordate is a vertebrate. Reason is also true and it explains exactly why - vertebrates start life with a notochord like all chordates, but that notochord is later replaced by a cartilaginous or bony vertebral column, the feature that actually defines Vertebrata.
Since R gives the developmental basis for A's claim, the code is (1), R correctly explains A.
NCERT Class 11 Biology, pages 46-47
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Q28 NEET 2021
Read the statements: (1) Metagenesis is observed in Helminths (2) Echinoderms are triploblastic and coelomate animals (3) Roundworms have organ-system level of body organisation. Which combination is correct?
- 1.(1) only
- 2.(2) and (3) onlyCorrect answer
- 3.(1) and (2) only
- 4.(1) and (3) only
Why option 2 is the answer
The trap: (2) and (3) are correct; metagenesis (alternation of generations) is a Cnidarian feature, not seen in Helminths.
What this is testing: checking three biology claims for accuracy before combining them.
(2) is correct - echinoderms are indeed triploblastic and coelomate. (3) is correct - roundworms (Aschelminthes) do show organ-system level organisation. Together these give option 2, (2) and (3) only.
(1) is the trap: metagenesis, the alternation between polyp and medusa generations, is a CNIDARIAN feature, not seen in helminths (flatworms and roundworms), which reproduce without this generational switch.
NCERT Class 11 Biology, pages 39-45
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Q29 NEET 2020
Organ-system level, bilateral symmetry, true coelomates with segmentation:
- 1.Annelida, Arthropoda and ChordataCorrect answer
- 2.Annelida, Arthropoda and Mollusca
- 3.Arthropoda, Mollusca and Chordata
- 4.Annelida, Mollusca and Chordata
Why option 1 is the answer
The trap: Annelida, Arthropoda and Chordata all show segmentation with a true coelom and organ-system organisation.
What this is testing: naming the three phyla that combine a true coelom with segmentation.
Annelida, Arthropoda and Chordata all show organ-system organisation, bilateral symmetry, a true coelom and body segmentation, making option 1 correct.
Mollusca is the trap swapped into options 2, 3 and 4 in place of one of the true three - molluscs are true coelomates and bilaterally symmetrical, but they are NOT segmented, their soft body organised instead into head-foot-visceral mass regions.
NCERT Class 11 Biology, pages 37-46
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Q30 NEET 2017
Which are aquatic mammals?
- 1.Whales, Dolphins, SealsCorrect answer
- 2.Dolphins, Seals, Trygon
- 3.Trygon, Whales, Seals
- 4.Seals, Dolphins, Sharks
Why option 1 is the answer
The trap: Whales, dolphins and seals are all aquatic mammals; Trygon and sharks are fish.
What this is testing: sorting three marine animals correctly by whether they are mammals or fish.
Whales, dolphins and seals are all aquatic mammals - they breathe air, are warm-blooded, and give birth to live young, despite living in water.
Trygon is the trap slipped into options 2 and 3 - it is a stingray, a cartilaginous fish, not a mammal, however similar its aquatic lifestyle looks. Sharks in option 4 are the same kind of trap, cartilaginous fish rather than mammals.
NCERT Class 11 Biology, page 51
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