Structural Organisation in Animals: the frog, tested properly

Free questions

30 solved MCQs, answer marked and reasoning written out

Every question below is free to read — no sign-up, no email. 2 of them are real questions from past NEET papers. The other 104 questions in this chapter are in the book and in practice access.

1. Q1 Multi-statement analysis

   The frog's excretory system: (i) consists of a pair of kidneys, ureters, cloaca and urinary bladder (ii) the kidneys are compact, dark red and bean-like (iii) each kidney has nephrons (uriniferous tubules) (iv) the frog excretes uric acid. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the frog excretes UREA and is ureotelic, so (iv) is wrong.

   What this is testing: what the frog throws out as its nitrogen waste.

   (i) is correct. The excretory system has a pair of kidneys, ureters, cloaca and urinary bladder.
   (ii) is correct. The kidneys are compact, dark red and bean-like.
   (iii) is correct. Each kidney is made of many nephrons, also called uriniferous tubules.
   (iv) is the trap. The frog passes out UREA, which makes it ureotelic. Uric acid is the waste of birds and reptiles, animals that must save water.

   So three are correct. Fix it by habitat: a frog lives in and near water and can afford watery urea, while a bird cannot.

   Kidneys, ureters, bladder, cloaca. The cloaca is the shared exit for urine, faeces and gametes alike.

   NCERT Class 11 Biology, page 82

2. Q2 Multi-statement analysis

   Sexual dimorphism in the frog: (i) male frogs possess vocal sacs (ii) male frogs bear a copulatory pad on the first digit of the forelimb (iii) both structures are absent in female frogs (iv) female frogs possess vocal sacs. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; vocal sacs are absent in females, so (iv) is wrong.

   What this is testing: which frog is the male and which the female.

   (i) is correct. Male frogs have vocal sacs.
   (ii) is correct. The male bears a copulatory pad on the first digit of the forelimb.
   (iii) is correct. Both structures are missing in the female.
   (iv) is the trap. It hands the vocal sacs to the FEMALE, directly contradicting (iii).

   So three are correct. Remember that both special marks belong to the male: the vocal sac amplifies his croak to call a mate, and the copulatory pad grips her during the mating clasp. The female carries neither, and if two statements in a list disagree about that, one is planted.

   Vocal sacs and the copulatory pad belong to the male. Both serve breeding, and neither appears in the female.

   NCERT Class 11 Biology, page 81

3. Q3 Multi-statement analysis

   Levels of organisation: (i) a tissue is a group of similar cells with intercellular substances performing a specific function (ii) all complex animals consist of only four basic types of tissues (iii) organs are formed by tissues in specific proportion and pattern (iv) two or more organs performing a common function form an organ system. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.Three
   4. 4.FourCorrect answer

   Why option 4 is the answer

   The trap: All four statements are correct.

   What this is testing: how cells build up into tissues, organs and organ systems.

   (i) is correct. A tissue is a group of similar cells with intercellular substances doing one particular job.
   (ii) is correct. Even the most complex animals are built from only four basic tissue types.
   (iii) is correct. Organs are made of tissues arranged in a definite proportion and pattern.
   (iv) is correct. Two or more organs that share a common function make an organ system.

   All four are correct. Statement (ii) is the one students fight, because "only four" in a sentence about complex animals sounds like a planted limit. Here it is the real textbook figure: epithelial, connective, muscular and neural.

   NCERT Class 11 Biology, page 79

4. Q4 Multi-statement analysis

   Frog circulation: (i) the sinus venosus joins the right atrium (ii) the sinus venosus receives blood through the vena cava (iii) the ventricle opens into the conus arteriosus (iv) the vascular system is of the open type. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the frog's vascular system is CLOSED, so (iv) is wrong.

   What this is testing: the route blood takes through the frog's heart, and the type of circulation.

   (i) is correct. The sinus venosus joins the right atrium.
   (ii) is correct. It receives blood through the vena cava.
   (iii) is correct. The ventricle opens into the conus arteriosus.
   (iv) is the trap. The frog's vascular system is CLOSED — blood stays inside vessels the whole way round.

   So three are correct. An open system, where blood pours into body spaces, belongs to animals like the cockroach. Every chordate you study, frog included, runs a closed circulation, so treat the word "open" in a frog question as a warning sign.

   Sinus venosus, right atrium, ventricle, conus arteriosus - and blood never leaves the vessels. Amphibians run a closed system.

   NCERT Class 11 Biology, page 82

5. Q5 Multi-statement analysis

   Frog respiration: (i) in water the skin acts as the respiratory organ (cutaneous) (ii) on land the buccal cavity, skin and lungs act as respiratory organs (iii) respiration by lungs is pulmonary respiration (iv) during aestivation and hibernation gaseous exchange occurs through the lungs. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; during aestivation and hibernation exchange occurs through the SKIN, so (iv) is wrong.

   What this is testing: which surface the frog breathes through when it is asleep for the season.

   (i) is correct. In water the skin alone works as the respiratory organ, which is cutaneous respiration.
   (ii) is correct. On land the buccal cavity, skin and lungs all take part.
   (iii) is correct. Breathing through lungs is pulmonary respiration.
   (iv) is the trap. During aestivation and hibernation gas exchange happens through the SKIN, not the lungs.

   So three are correct. Think about what a buried, motionless frog can actually do: it is not pumping its lungs, but its moist skin keeps exchanging gases quietly all through the sleep. Skin is the frog's fallback in every situation.

   Skin in water, skin plus lungs plus buccal cavity on land. A frog never stops breathing through its skin, which is why it must stay moist.

   NCERT Class 11 Biology, page 82

6. Q6 Multi-statement analysis

   The frog's brain: (i) the forebrain includes olfactory lobes, cerebral hemispheres and diencephalon (ii) the midbrain has a pair of optic lobes (iii) the hindbrain has the cerebellum and medulla oblongata (iv) there are twelve pairs of cranial nerves. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.ThreeCorrect answer
   4. 4.Four

   Why option 3 is the answer

   The trap: (i)–(iii) correct; the frog has TEN pairs of cranial nerves, so (iv) is wrong.

   What this is testing: the parts of the frog's brain, and the number of cranial nerves.

   (i) is correct. The forebrain has the olfactory lobes, cerebral hemispheres and diencephalon.
   (ii) is correct. The midbrain carries a pair of optic lobes.
   (iii) is correct. The hindbrain has the cerebellum and medulla oblongata.
   (iv) is the trap. The frog has TEN pairs of cranial nerves, not twelve.

   So three are correct. Twelve is the human figure, and it slips in easily because the three brain divisions listed before it are shared with us. Keep one number for each animal: frog ten, human twelve.

   Forebrain, midbrain, hindbrain - olfactory to optic to cerebellum. The same three divisions as in a human brain.

   NCERT Class 11 Biology, page 83

7. Q7 Multi-statement analysis

   The skin of the frog: (i) is smooth and slippery due to mucus (ii) is always maintained in a moist condition (iii) is olive green with dark irregular spots on the dorsal side (iv) is uniformly pale yellow on the ventral side. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.Three
   4. 4.FourCorrect answer

   Why option 4 is the answer

   The trap: All four are correct.

   What this is testing: the look and feel of the frog's skin.

   (i) is correct. Mucus makes the skin smooth and slippery.
   (ii) is correct. The skin is always kept moist.
   (iii) is correct. The dorsal side is olive green with dark irregular spots.
   (iv) is correct. The ventral side is uniformly pale yellow.

   All four are correct. Students doubt (ii) because they picture a frog sitting on dry land, but the moist skin is not optional — it is a breathing surface, and gases can only cross it while it is wet. The mucus in (i) is exactly what keeps the condition in (ii) true.

   NCERT Class 11 Biology, page 80

8. Q8 Multi-statement analysis

   Frog male reproductive system: (i) a pair of yellowish ovoid testes is present (ii) the testes adhere to the kidneys by the mesorchium (iii) vasa efferentia are 10–12 in number (iv) the vasa efferentia open into Bidder's canal. How many are correct?

   1. 1.One
   2. 2.Two
   3. 3.Three
   4. 4.FourCorrect answer

   Why option 4 is the answer

   The trap: All four are correct.

   What this is testing: the plumbing of the frog's male reproductive system.

   (i) is correct. There is a pair of yellowish ovoid testes.
   (ii) is correct. They are attached to the kidneys by a double fold of membrane called the mesorchium.
   (iii) is correct. The vasa efferentia number 10 to 12.
   (iv) is correct. They enter the kidney and open into Bidder's canal.

   All four are correct. The statement students strike out is (ii), because they remember that the female's ovaries have NO connection with the kidneys and wrongly apply the same rule to the male. The male is the opposite case: his sperm ducts run through the kidney.

   NCERT Class 11 Biology, page 83

9. Q9 Assertion and Reason

   AssertionFrogs are not seen during peak summer and winter.

   ReasonThe summer sleep of the frog is called hibernation and its winter sleep is called aestivation.

   1. 1.Both A and R are true and R is the correct explanation of A
   2. 2.Both A and R are true but R is not the correct explanation of A
   3. 3.A is true but R is falseCorrect answer
   4. 4.A is false but R is true

   Why option 3 is the answer

   The trap: A is true; the terms are reversed — summer sleep is AESTIVATION and winter sleep is HIBERNATION, so R is false.

   What this is testing: which season goes with which kind of sleep.

   A says frogs are not seen during peak summer and winter. True — they are asleep underground.

   R says summer sleep is hibernation and winter sleep is aestivation. False. The two names have been swapped: summer sleep is AESTIVATION and winter sleep is HIBERNATION.

   A true and R false is code (3).

   The trap: A is comfortably true, and a true A pulls students into ticking (1) without checking R closely. The swap is the whole question. Aestivation for the hot season, hibernation for the cold one.

   NCERT Class 11 Biology, page 80

10. Q10 Assertion and Reason

    AssertionThe frog is a uricotelic animal that excretes uric acid.

    ReasonThe frog excretes urea and is therefore described as ureotelic.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false — the frog is ureotelic; R is true.

    What this is testing: which nitrogen waste the frog passes out.

    A says the frog is uricotelic and excretes uric acid. False. The frog excretes UREA.

    R says the frog excretes urea and is therefore ureotelic. True, and it states the very fact that makes A false.

    A false and R true is code (4).

    The trap: A is placed first and reads confidently, and uricotelic and ureotelic differ by only a few letters. Split them at the root: uric acid gives uricoTELIC, in birds and reptiles; urea gives ureoTELIC, in the frog. When A and R contradict each other outright, one of them must go.

    NCERT Class 11 Biology, page 83

11. Q11 Assertion and Reason

    AssertionThe kidneys of the frog lie on both sides of the vertebral column.

    ReasonThe kidneys of the frog are compact, dark red and bean-like structures.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of the kidneys; their shape and colour are parallel features and do not explain their position.

    What this is testing: whether a description of shape can explain a position.

    A says the frog's kidneys lie on both sides of the vertebral column. True.

    R says the kidneys are compact, dark red and bean-like. Also true.

    But R is about what the kidneys LOOK like, and A is about WHERE they sit. Being bean-shaped and dark red does not place an organ beside the backbone. Two true lines with no causal link between them is code (2).

    The trap: both lines come from the same sentence of the chapter, so they feel connected. They are parallel facts, not cause and effect. Always ask whether R answers the question "why" — here it answers "what does it look like".

    NCERT Class 11 Biology, page 82

12. Q12 Assertion and Reason

    AssertionThe heart of the frog has four chambers.

    ReasonThe heart of the frog has two atria and a single ventricle.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false — the frog heart is three-chambered; R is true.

    What this is testing: how many chambers the frog's heart has.

    A says the heart has four chambers. False. The frog's heart is THREE-chambered.

    R says the heart has two atria and a single ventricle. True — and two plus one is three, which is precisely what proves A wrong.

    A false and R true is code (4).

    The trap: students who know that R is true often assume A must be true as well, since both talk about chambers. Read R as a sum. If R gives you the parts, add them up before you accept the total offered in A.

    NCERT Class 11 Biology, page 82

13. Q13 Assertion and Reason

    AssertionThe heart of the frog is covered by a pericardium.

    ReasonThe heart of the frog has three chambers, two atria and one ventricle.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of the frog's heart; the chamber number is a parallel structural fact and does not explain the pericardial covering.

    What this is testing: whether the number of chambers explains the covering over the heart.

    A says the frog's heart is covered by a pericardium. True.

    R says the heart has three chambers, two atria and one ventricle. True as well.

    Both lines are correct, but a chamber count cannot explain why a membrane wraps the organ. They are two separate facts about the same heart, so the answer is code (2).

    The trap: two familiar true statements about one organ pull students straight to code (1). Slow down and put "because" between them — the heart has a pericardium BECAUSE it has three chambers makes no sense, and that settles it.

    NCERT Class 11 Biology, page 82

14. Q14 Assertion and Reason

    AssertionThe frog has a well-developed closed vascular system.

    ReasonFrogs also possess a lymphatic system consisting of lymph, lymph channels and lymph nodes.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true circulatory facts running in parallel; the lymphatic system does not explain the closed blood vascular system.

    What this is testing: whether the lymphatic system explains the blood vascular system.

    A says the frog has a well-developed closed vascular system. True.

    R says the frog also has a lymphatic system of lymph, lymph channels and lymph nodes. True as well.

    Both are correct, but they describe two different systems standing side by side. The presence of lymph nodes does not make the blood system closed. Two true but unlinked statements is code (2).

    The trap: the word "also" in R is your signal. It announces an addition, not a cause, and an addition can never be the correct explanation of A.

    NCERT Class 11 Biology, page 82

15. Q15 Assertion and Reason

    AssertionA mature female frog can lay 2500 to 3000 ova at a time.

    ReasonFertilisation in the frog is external and takes place in water.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true reproductive facts running in parallel; external fertilisation is not offered here as the cause of the egg number.

    What this is testing: whether external fertilisation is offered as the cause of the egg number.

    A says a mature female lays 2500 to 3000 ova at a time. True.

    R says fertilisation is external and happens in water. Also true.

    Both are correct facts about frog reproduction, but R as written does not explain A — it states where fertilisation occurs, not why the number of eggs is so large. Two true parallel facts give code (2).

    The trap: the two facts sit close together in the chapter and feel like a story, so students reach for code (1). Judge only what R actually says, not the link you supply yourself.

    NCERT Class 11 Biology, page 84

16. Q16 Assertion and Reason

    AssertionThe RBCs of the frog are nucleated.

    ReasonThe RBCs of the frog contain the red pigment haemoglobin.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of ACorrect answer
    3. 3.A is true but R is false
    4. 4.A is false but R is true

    Why option 2 is the answer

    The trap: Both are true of frog RBCs; the presence of haemoglobin is a parallel property and does not explain the retention of the nucleus.

    What this is testing: whether haemoglobin explains the nucleus in a frog's red cell.

    A says frog RBCs are nucleated. True — unlike our mature red cells, the frog's keep their nucleus.

    R says frog RBCs contain the red pigment haemoglobin. Also true.

    Both lines are correct, but carrying haemoglobin has nothing to do with keeping a nucleus; our own RBCs carry haemoglobin and have no nucleus at all. Two true unlinked facts is code (2).

    The trap: both statements are about the same cell, which makes code (1) feel natural. Use the human red cell as your test case — it separates the two properties immediately.

    NCERT Class 11 Biology, page 82

17. Q17 Assertion and Reason

    AssertionThe eye of the frog is protected in water by the tympanum.

    ReasonThe eye of the frog is covered by a nictitating membrane that protects it while in water.

    1. 1.Both A and R are true and R is the correct explanation of A
    2. 2.Both A and R are true but R is not the correct explanation of A
    3. 3.A is true but R is false
    4. 4.A is false but R is trueCorrect answer

    Why option 4 is the answer

    The trap: A is false — the tympanum is the hearing membrane; R is true (structure swap).

    What this is testing: which membrane protects the frog's eye.

    A says the eye is protected in water by the tympanum. False. The tympanum is the hearing membrane on the side of the head, and it has nothing to do with the eye.

    R says the eye is covered by a nictitating membrane that protects it in water. True.

    A false and R true is code (4).

    The trap: a straight structure swap. A borrows the name of the ear drum and attaches it to the eye. Keep the pair fixed: tympanum for sound, nictitating membrane for the eye.

    NCERT Class 11 Biology, page 80

18. Q18 Statement I and Statement II

    Statement IDuring hibernation the frog respires through its lungs.

    Statement IIOn land the buccal cavity, skin and lungs act as respiratory organs.

    1. 1.Both Statement I and Statement II are correct
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrect
    4. 4.Statement I is incorrect but Statement II is correctCorrect answer

    Why option 4 is the answer

    The trap: I incorrect (gaseous exchange occurs through the SKIN during hibernation); II correct.

    What this is testing: which organ works during the frog's seasonal sleep.

    Statement I says the frog respires through its lungs during hibernation. Wrong. Gas exchange during hibernation and aestivation happens through the SKIN.

    Statement II says that on land the buccal cavity, skin and lungs all act as respiratory organs. Correct.

    I incorrect and II correct gives (4).

    The trap: Statement II truthfully lists the lungs among the land organs, which makes the lungs in Statement I feel right too. A buried, motionless frog is not pumping its lungs. Skin is the frog's fallback breathing surface in every hard situation.

    NCERT Class 11 Biology, page 82

19. Q19 Statement I and Statement II

    Statement IThere are ten pairs of cranial nerves in the frog.

    Statement IIThe midbrain of the frog is characterised by a pair of optic lobes.

    1. 1.Both Statement I and Statement II are correctCorrect answer
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrect
    4. 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: the number of cranial nerves and the contents of the midbrain.

    Statement I says the frog has ten pairs of cranial nerves. Correct.

    Statement II says the midbrain carries a pair of optic lobes. Correct.

    Both are correct, so the answer is (1).

    The trap: twelve pairs is the human figure, and it is so well drilled that many students read ten and mark Statement I false. Keep one number to one animal — frog ten, human twelve. Note also the pairing in Statement II: optic lobes are in the MIDbrain, not the forebrain.

    NCERT Class 11 Biology, page 83

20. Q20 Statement I and Statement II

    Statement IThe ovaries of the frog have a functional connection with the kidneys.

    Statement IIIn female frogs the ureters and oviducts open separately into the cloaca.

    1. 1.Both Statement I and Statement II are correct
    2. 2.Both Statement I and Statement II are incorrect
    3. 3.Statement I is correct but Statement II is incorrect
    4. 4.Statement I is incorrect but Statement II is correctCorrect answer

    Why option 4 is the answer

    The trap: I incorrect (there is NO functional connection); II correct.

    What this is testing: whether the female frog's ovaries are joined to her kidneys.

    Statement I says the ovaries have a functional connection with the kidneys. Wrong. There is NO such connection in the female.

    Statement II says the ureters and oviducts open separately into the cloaca in the female frog. Correct, and it fits: since the two systems are not joined, their ducts arrive at the cloaca separately.

    I incorrect and II correct gives (4).

    The trap: in the MALE the sperm ducts really do run through the kidney. Students carry that picture over to the female. The two sexes are built differently here.

    NCERT Class 11 Biology, page 84

21. Q21 Match the columns

    Match the sense organ with the sense it serves in the frog:

    Column I	Column II
    (a) Sensory papillae	(i) hearing
    (b) Taste buds	(ii) touch
    (c) Nasal epithelium	(iii) taste
    (d) Tympanum	(iv) smell

    1. 1.(a)-(iii), (b)-(ii), (c)-(iv), (d)-(i)
    2. 2.(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)
    3. 3.(a)-(i), (b)-(iii), (c)-(iv), (d)-(ii)
    4. 4.(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)Correct answer

    Why option 4 is the answer

    The trap: Sensory papillae-touch, Taste buds-taste, Nasal epithelium-smell, Tympanum-hearing.

    What this is testing: the frog's four sense organs and the sense each one serves.

    Sensory papillae serve touch, so (a)-(ii). Taste buds serve taste, so (b)-(iii). The nasal epithelium serves smell, so (c)-(iv). The tympanum serves hearing, so (d)-(i). That is option (4).

    Why the others fail: option (1) swaps touch and taste between the papillae and the taste buds. Option (2) gives smell to the taste buds. Option (3) makes the sensory papillae the hearing organ and the tympanum the touch organ.

    The trap: sensory papillae and taste buds are both small bumps in or on the body, so their senses swap easily. Papillae on the skin feel; buds in the mouth taste.

    NCERT Class 11 Biology, page 83

22. Q22 Match the columns

    Match the reproductive structure with its description:

    Column I	Column II
    (a) Mesorchium	(iv) 10–12 in number
    (b) Vasa efferentia	(ii) receives the vasa efferentia
    (c) Bidder's canal	(iii) passes faeces, urine and sperms
    (d) Cloaca	(i) double fold of peritoneum holding the testes

    1. 1.(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
    2. 2.(a)-(i), (b)-(iv), (c)-(ii), (d)-(iii)Correct answer
    3. 3.(a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)
    4. 4.(a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)

    Why option 2 is the answer

    The trap: Mesorchium-peritoneal fold, Vasa efferentia-10 to 12, Bidder's canal-receives them, Cloaca-common outlet.

    What this is testing: four named parts of the male frog's reproductive tract.

    The mesorchium is the double fold of peritoneum that holds the testes, so (a)-(i). The vasa efferentia are 10 to 12 in number, so (b)-(iv). Bidder's canal receives the vasa efferentia, so (c)-(ii). The cloaca passes out faeces, urine and sperms, so (d)-(iii). That is option (2).

    Why the others fail: option (1) swaps the mesorchium and vasa efferentia, so the membrane gets the number. Option (3) makes Bidder's canal the numbered structure. Option (4) calls the mesorchium the common outlet.

    The trap: the number 10 to 12 belongs to the ducts, not to the membrane.

    NCERT Class 11 Biology, page 83

23. Q23 Match the columns

    Match the respiration type with its site in the frog:

    Column I	Column II
    (a) Cutaneous respiration	(i) buccal cavity, on land
    (b) Pulmonary respiration	(iii) skin, in water
    (c) Buccal respiration	(iv) exchange through the skin
    (d) Hibernation/aestivation	(ii) lungs, on land

    1. 1.(a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)
    2. 2.(a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)Correct answer
    3. 3.(a)-(iii), (b)-(i), (c)-(ii), (d)-(iv)
    4. 4.(a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)

    Why option 2 is the answer

    The trap: Cutaneous-skin in water, Pulmonary-lungs on land, Buccal-buccal cavity, during dormancy-skin.

    What this is testing: the name of each kind of breathing and the surface it uses.

    Cutaneous respiration uses the skin in water, so (a)-(iii). Pulmonary respiration uses the lungs on land, so (b)-(ii). Buccal respiration uses the buccal cavity on land, so (c)-(i). During hibernation and aestivation exchange is through the skin, so (d)-(iv). That is option (2).

    Why the others fail: option (1) swaps cutaneous and pulmonary, putting the skin in the lung slot. Option (3) exchanges pulmonary and buccal. Option (4) sends cutaneous respiration to the dormancy line.

    The trap: cutaneous and pulmonary swapping. Cutis means skin, pulmo means lung.

    NCERT Class 11 Biology, page 82

24. Q24 Match the columns

    Match the organ with its system in the frog:

    Column I	Column II
    (a) Kidney	(i) respiratory system
    (b) Testis	(ii) excretory system
    (c) Lung	(iii) digestive system
    (d) Stomach	(iv) male reproductive system

    1. 1.(a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)Correct answer
    2. 2.(a)-(iv), (b)-(ii), (c)-(i), (d)-(iii)
    3. 3.(a)-(ii), (b)-(i), (c)-(iv), (d)-(iii)
    4. 4.(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)

    Why option 1 is the answer

    The trap: Kidney-excretory, Testis-male reproductive, Lung-respiratory, Stomach-digestive.

    What this is testing: which organ belongs to which body system in the frog.

    The kidney belongs to the excretory system, so (a)-(ii). The testis belongs to the male reproductive system, so (b)-(iv). The lung belongs to the respiratory system, so (c)-(i). The stomach belongs to the digestive system, so (d)-(iii). That is option (1).

    Why the others fail: option (2) swaps kidney and testis, putting the kidney in the reproductive system. Option (3) exchanges testis and lung. Option (4) assigns the kidney to digestion.

    The trap: in the male frog the sperm ducts really do pass through the kidney, and that genuine link tempts students towards option (2). Shared plumbing does not move an organ into another system.

    NCERT Class 11 Biology, page 82

25. Q25 Exception / incorrect

    All are true of the frog's limbs EXCEPT:

    1. 1.forelimbs end in four digits
    2. 2.hind limbs end in five digits
    3. 3.forelimbs are larger than hind limbsCorrect answer
    4. 4.hind limbs are muscular

    Why option 3 is the answer

    The trap: The HIND limbs are larger and more muscular.

    What this is testing: which pair of limbs is the bigger one.

    The forelimbs end in four digits, the hind limbs end in five digits, and the hind limbs are muscular — all true, so none of those is the exception.

    The exception is "forelimbs are larger than hind limbs". It is the other way round: the HIND limbs are larger and more muscular.

    The trap: the statement is a clean reversal, and reversals read smoothly because every word in them is a real frog word. Tie size to function — the hind limbs do the leaping and the swimming, so they must be the heavier pair.

    NCERT Class 11 Biology, page 81

26. Q26 Exception / incorrect

    All are true of the frog's blood EXCEPT:

    1. 1.RBCs are nucleated
    2. 2.RBCs contain haemoglobin
    3. 3.blood has plasma and cells
    4. 4.RBCs are enucleateCorrect answer

    Why option 4 is the answer

    The trap: Frog RBCs ARE nucleated.

    What this is testing: whether the frog's red blood cells keep their nucleus.

    RBCs are nucleated, RBCs contain haemoglobin, and blood is made of plasma and cells — all true of the frog.

    The exception is "RBCs are enucleate", which means having no nucleus. That is the human mature red cell, not the frog's.

    The trap: options 1 and 4 are flat opposites, so one of them is the planted error, and the paper is betting you will pick the one you learned in human physiology. Keep the two animals apart. Frog red cells carry a nucleus; ours lose it as they mature.

    NCERT Class 11 Biology, page 82

27. Q27 Sequence / ordering

    Correct path of air during pulmonary respiration in the frog:

    1. 1.lungs → buccal cavity → nostrils
    2. 2.buccal cavity → nostrils → lungs
    3. 3.nostrils → buccal cavity → lungsCorrect answer
    4. 4.nostrils → lungs → buccal cavity

    Why option 3 is the answer

    The trap: Air enters through the nostrils into the buccal cavity and then to the lungs.

    What this is testing: the path air follows when the frog uses its lungs.

    Air enters through the nostrils, passes into the buccal cavity, and is then pushed on into the lungs. That is option 3.

    Why the others fail: option 1 runs the whole route backwards, from lungs to nostrils. Option 2 starts inside the buccal cavity and makes air leave by the nostrils before reaching the lungs. Option 4 sends air to the lungs first and the buccal cavity afterwards.

    The trap: the buccal cavity also works as a breathing surface in its own right, which makes students treat it as an endpoint. In pulmonary respiration it is only the stage on the way in.

    NCERT Class 11 Biology, page 82

28. Q28 Sequence / ordering

    Correct antero-posterior order of the frog's brain regions:

    1. 1.hindbrain → midbrain → forebrain
    2. 2.forebrain → midbrain → hindbrainCorrect answer
    3. 3.midbrain → forebrain → hindbrain
    4. 4.forebrain → hindbrain → midbrain

    Why option 2 is the answer

    The trap: Forebrain → midbrain → hindbrain, the medulla continuing into the spinal cord.

    What this is testing: the order of the brain regions from front to back.

    Reading from the front of the head backwards: forebrain, then midbrain, then hindbrain, whose medulla oblongata passes out of the skull and continues as the spinal cord. That is option 2.

    Why the others fail: option 1 is the same list read from the back forwards. Option 3 puts the midbrain in front of the forebrain, and option 4 buries the midbrain behind the hindbrain.

    The trap: option 1, the correct order reversed. The names carry the answer — fore means front, hind means back — so let the words place themselves before you look at the choices.

    NCERT Class 11 Biology, page 83

29. Q29 NEET 2026

    Choose the correct statements regarding a frog's anatomy: (A) The hepatic portal system is the special venous connection between liver and intestine (B) There are twelve pairs of cranial nerves arising from the brain (C) The ureters and oviducts open separately into the cloaca in female frogs (D) The hindbrain consists of cerebellum, medulla oblongata and optic lobes (E) The sinus venosus joins the right atrium of the heart.

    1. 1.A, B and D only
    2. 2.B, D and E only
    3. 3.A, C and E onlyCorrect answer
    4. 4.A, B, C and D only

    Why option 3 is the answer

    The trap: (A), (C) and (E) are correct. (B) is wrong: frogs have ten, not twelve, pairs of cranial nerves. (D) is wrong: the optic lobes belong to the midbrain, not the hindbrain.

    What this is testing: five separate anatomy facts, sorted true from false in one question.

    (A), (C) and (E) are correct, which is option 3. The hepatic portal system does link liver and intestine, the female's ureters and oviducts do open separately into the cloaca, and the sinus venosus does join the right atrium.

    (B) is wrong: the frog has TEN pairs of cranial nerves, not twelve — the human figure again. (D) is wrong: the optic lobes belong to the midbrain, so the hindbrain has only the cerebellum and medulla oblongata.

    The trap: both planted errors are true statements with one part moved. Check each item alone.

    NCERT Class 11 Biology, pages 82-84

30. Q30 NEET 2024 (Re-Exam)

    In which connective tissues do cells secrete fibres of collagen or elastin? (A) Cartilage (B) Bone (C) Adipose tissue (D) Blood (E) Areolar tissue.

    1. 1.A, C and D only
    2. 2.B, C and E only
    3. 3.A, B, C and D only
    4. 4.A, B and E onlyCorrect answer

    Why option 4 is the answer

    The trap: Cartilage, bone and areolar tissue all have cells that secrete fibrous proteins (collagen/elastin) into their matrix. Adipose tissue cells store fat rather than secrete such fibres, and blood's matrix (plasma) is fibre-free.

    What this is testing: which connective tissues have cells that secrete collagen or elastin fibres.

    Cartilage, bone and areolar tissue all have cells that lay down fibrous protein in their matrix, which is option 4.

    Why the others are wrong: (C) adipose tissue cells store fat rather than secrete fibres, and (D) blood has a fluid matrix, plasma, with no fibres in it. Every wrong option includes adipose tissue or blood, or both.

    The trap: all five items are genuine connective tissues, so the word "connective" will not sort them. Ask instead what each one's matrix is made of — fibres, or fat, or fluid.

    NCERT Class 11 Biology, page 79