Biological Classification: solved NEET MCQs you can read here

Free questions

30 solved MCQs, answer marked and reasoning written out

Every question below is free to read — no sign-up, no email. 3 of them are real questions from past NEET papers. The other 189 questions in this chapter are in the book and in practice access.

1. Q1 Multi-statement analysis

   History of virus discovery: (i) Ivanowsky (1892) recognised certain microbes as the cause of the mosaic disease of tobacco (ii) Beijerinck (1898) demonstrated the infectious fluid and called it Contagium vivum fluidum (iii) W.M. Stanley (1935) showed that viruses could be crystallised (iv) crystals of the virus consist largely of carbohydrates. 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 crystals consist largely of PROTEINS, so (iv) is wrong.

   What this is testing: the three names in the history of virus discovery, and what the crystals are made of.

   (i) is correct. Ivanowsky in 1892 traced the tobacco mosaic disease to microbes smaller than bacteria.
   (ii) is correct. Beijerinck in 1898 showed the sap could infect, and called it Contagium vivum fluidum.
   (iii) is correct. W.M. Stanley in 1935 showed viruses could be crystallised.
   (iv) is the trap. Those crystals are made largely of PROTEINS, not carbohydrates.

   So three are correct.

   A virus is protein plus nucleic acid. Carbohydrate is not part of that pair, so the line fails on the one word it changed.

   NCERT Class 11 Biology, page 20

2. Q2 Multi-statement analysis

   Basidiomycetes: (i) include mushrooms, bracket fungi and puffballs (ii) asexual spores are generally not found (iii) sex organs are absent and plasmogamy occurs by fusion of two vegetative or somatic cells (iv) four basidiospores are produced endogenously within the basidium. 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 four basidiospores are produced EXOGENOUSLY on the basidium, so (iv) is wrong.

   What this is testing: how basidiospores are produced.

   (i) is correct. Mushrooms, bracket fungi and puffballs are basidiomycetes.
   (ii) is correct. Asexual spores are generally not found in this group.
   (iii) is correct. There are no sex organs, so plasmogamy happens when two vegetative or somatic cells fuse.
   (iv) is the trap. The four basidiospores are produced EXOGENOUSLY, sitting on the outside of the club-shaped basidium.

   So three are correct.

   Pair the two groups in your head: ascospores are made inside the ascus, basidiospores outside the basidium. The question swaps only that one word.

   NCERT Class 11 Biology, page 18

3. Q3 Multi-statement analysis

   Limitations of the two-kingdom system: (i) it did not distinguish eukaryotes from prokaryotes (ii) it did not distinguish unicellular from multicellular (iii) it did not separate photosynthetic from non-photosynthetic forms (iv) it grouped fungi along with green plants. 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 were limitations of the two-kingdom system.

   What this is testing: why the old two-kingdom system had to be replaced.

   All four are correct.
   (i) It did not separate eukaryotes from prokaryotes.
   (ii) It did not separate unicellular from multicellular organisms.
   (iii) It did not separate photosynthetic forms from non-photosynthetic ones.
   (iv) It parked the fungi with the green plants, though fungi have no chlorophyll.

   So all four are correct.

   The trap is that every line is a complaint, and four complaints feel like too many to all be true. They are all true, and together they are the reason Whittaker's five kingdom system was needed.

   NCERT Class 11 Biology, page 10

4. Q4 Multi-statement analysis

   Kingdom Protista: (i) includes all single-celled eukaryotes (ii) the boundaries are not well defined (iii) members are primarily aquatic (iv) they reproduce only asexually. 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; protists reproduce asexually AND sexually, so (iv) is wrong.

   What this is testing: the general features of Kingdom Protista.

   (i) is correct. All single-celled eukaryotes are placed here.
   (ii) is correct. The boundaries of this kingdom are not well defined, and workers disagree about what belongs in it.
   (iii) is correct. Protists are primarily aquatic.
   (iv) is the trap. They reproduce asexually AND sexually, the sexual method involving fusion of two cells.

   So three are correct.

   The word 'only' is again the planted error. Before accepting any statement that contains only, all or never, ask whether the book actually shuts that door.

   NCERT Class 11 Biology, page 14

5. Q5 Multi-statement analysis

   Fungal reproduction: (i) vegetative means include fragmentation, fission and budding (ii) asexual reproduction is by spores such as conidia, sporangiospores or zoospores (iii) sexual reproduction is by oospores, ascospores and basidiospores (iv) sexual spores are produced in the sporangium. 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 sporangium bears ASEXUAL spores, so (iv) is wrong.

   What this is testing: which spores come from sexual reproduction and which do not.

   (i) is correct. Vegetative means include fragmentation, fission and budding.
   (ii) is correct. The asexual spores are conidia, sporangiospores and zoospores.
   (iii) is correct. The sexual spores are oospores, ascospores and basidiospores.
   (iv) is the trap. The sporangium bears ASEXUAL spores — sporangiospores, as the name in (ii) already tells you.

   So three are correct.

   The answer is hidden in the word itself. Sporangiospores are named after the sporangium, and (ii) has already placed them on the asexual side.

   NCERT Class 11 Biology, page 17

6. Q6 Multi-statement analysis

   Whittaker's (1969) criteria for classification: (i) cell structure (ii) body organisation (iii) mode of nutrition (iv) reproduction (v) phylogenetic relationships. How many criteria?

   1. 1.Two
   2. 2.Three
   3. 3.Four
   4. 4.FiveCorrect answer

   Why option 4 is the answer

   The trap: Whittaker used all five criteria.

   What this is testing: plain recall of the criteria Whittaker used in 1969.

   All five are his criteria: cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships. So the answer is five.

   The trap is the last one. Phylogenetic relationships means relationships by descent, that is, who evolved from whom, and it sounds like a modern addition rather than part of a 1969 scheme. It is on Whittaker's list.

   These five are worth learning as a set, because the same list is asked as a count, as a match and as an exception question.

   NCERT Class 11 Biology, page 11

7. Q7 Multi-statement analysis

   Bacteria as a group: (i) they are the sole members of Kingdom Monera (ii) they are the most abundant micro-organisms (iii) they occur in extreme habitats such as hot springs and deserts (iv) they show the least metabolic diversity of all organisms. 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; bacteria show the MOST extensive metabolic diversity, so (iv) is wrong.

   What this is testing: how varied bacteria are in the way they live.

   (i) is correct. Bacteria are the sole members of Kingdom Monera.
   (ii) is correct. They are the most abundant micro-organisms.
   (iii) is correct. They are found in extreme habitats such as hot springs, deserts, snow and deep oceans.
   (iv) is the trap, and it is the reverse of the truth. Bacteria show the MOST extensive metabolic diversity of any group of organisms.

   So three are correct.

   Read (iii) and (iv) against each other. Anything that can live in a hot spring and in snow must have many ways of getting energy, not few.

   NCERT Class 11 Biology, page 12

8. Q8 Multi-statement analysis

   Regarding viral protein coat: (i) the protein coat is called the capsid (ii) it is made of small subunits called capsomeres (iii) the capsid protects the nucleic acid (iv) the capsomeres are arranged in random fashion. 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; capsomeres are arranged in helical or polyhedral geometric forms, so (iv) is wrong.

   What this is testing: the structure of the protein coat of a virus.

   (i) is correct. The protein coat is the capsid.
   (ii) is correct. It is built from small units called capsomeres.
   (iii) is correct. The capsid protects the nucleic acid inside.
   (iv) is the trap. The capsomeres are not random. They are arranged in geometric forms, either helical or polyhedral, and that regular packing is why a virus can be crystallised at all.

   So three are correct.

   Random arrangement and crystal shape cannot both be true. Crystals form only when units repeat in a fixed pattern.

   NCERT Class 11 Biology, page 20

9. Q9 Assertion and Reason

   AssertionProtista forms a link with the other kingdoms.

   ReasonThe boundaries of Kingdom Protista are not well defined.

   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 Protista; the vagueness of its boundaries is a parallel fact and does not explain its linking position.

   What this is testing: whether a true reason is the RIGHT reason.

   A says Protista forms a link with the other kingdoms. True — it holds organisms with plant-like, animal-like and fungus-like habits.
   R says the boundaries of Kingdom Protista are not well defined. Also true; the chapter says so plainly.

   Both true, but R does not explain A, so the code is (2). The vague boundary is a difficulty for taxonomists; the linking position is about what the members are like.

   The trap: two true lines about the same kingdom feel connected. Being about the same topic is not the same as being the cause.

   NCERT Class 11 Biology, page 14

10. Q10 Assertion and Reason

    AssertionEuglena behaves like a heterotroph when deprived of sunlight.

    ReasonEuglenoids possess a protein-rich layer called the pellicle instead of a cell wall.

    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 euglenoids; the pellicle is a parallel structural feature and does not explain the shift to heterotrophy in the dark.

    What this is testing: whether the pellicle has anything to do with how Euglena feeds.

    A says Euglena behaves like a heterotroph when kept away from sunlight. True.
    R says euglenoids have a protein-rich pellicle instead of a cell wall. True.

    Both true, but R does not explain A, so the code is (2). The pellicle is about the body covering and flexibility; the shift to heterotrophy is about nutrition when photosynthesis cannot run.

    The trap: both lines come from the same paragraph of the book, and nearness on the page feels like cause. Ask whether R answers 'why does it feed that way?'. A body covering does not.

    NCERT Class 11 Biology, page 15

11. Q11 Assertion and Reason

    AssertionThe cell wall of a bacterium determines the shape of the cell.

    ReasonBacteria are grouped into four categories based on their shape.

    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 bacteria; the four shape categories are a parallel classification and do not explain the wall's shape-determining role.

    What this is testing: whether a classification of shapes explains what makes the shape.

    A says the bacterial cell wall determines the shape of the cell. True.
    R says bacteria are grouped into four categories on the basis of shape. True — coccus, bacillus, vibrio and spirillum.

    Both true, but R does not explain A, so the code is (2). R tells you how we sort bacteria; A tells you what physically holds each one in its form.

    The trap: the word 'shape' appears in both lines, and a shared word feels like a link. A description of the result is not an explanation of the cause.

    NCERT Class 11 Biology, page 12

12. Q12 Assertion and Reason

    AssertionViroids consist of a free RNA of high molecular weight.

    ReasonT.O. Diener discovered a new infectious agent that was smaller than viruses and had a free RNA of low molecular weight.

    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; R is true.

    What this is testing: the molecular weight of viroid RNA.

    A says viroids consist of free RNA of high molecular weight. False. It is of LOW molecular weight.
    R says T.O. Diener discovered an infectious agent smaller than viruses, with free RNA of low molecular weight. True.

    A false and R true is code (4).

    The trap: A and R differ in one word, and R supplies the correction to A directly underneath. Whenever the two lines make opposite claims about the same quantity, read R carefully; it usually carries the version the book actually gives.

    NCERT Class 11 Biology, page 21

13. Q13 Assertion and Reason

    AssertionMycoplasma can survive in habitats where free oxygen is unavailable.

    ReasonMycoplasma are organisms that completely lack a cell wall and are the smallest living cells known.

    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 Mycoplasma; the absence of a wall and their small size are parallel features and do not explain their ability to survive without oxygen.

    What this is testing: whether the absence of a cell wall explains life without oxygen.

    A says Mycoplasma can survive where free oxygen is not available. True.
    R says Mycoplasma completely lack a cell wall and are the smallest living cells known. True.

    Both true, but R does not explain A, so the code is (2). Having no wall and being tiny are matters of structure; surviving without oxygen is a matter of how the cell gets its energy.

    The trap: all three facts sit in the same sentence of the book, and students take nearness on the page for cause and effect.

    NCERT Class 11 Biology, page 14

14. Q14 Assertion and Reason

    AssertionWhittaker proposed a five kingdom classification in 1969.

    ReasonThe main criteria of his classification included cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships.

    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 Whittaker's scheme; the list of criteria is a parallel fact and does not explain the year or authorship.

    What this is testing: whether a list of criteria explains who proposed the system and when.

    A says Whittaker proposed the five kingdom classification in 1969. True.
    R lists his criteria — cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships. True.

    Both true, but R does not explain A, so the code is (2). R tells you what the system was built on; it cannot tell you who built it or in which year.

    The trap: R is a correct and impressive-looking list. Ask what A actually claims. A claims authorship and a date, and no list of criteria can be the reason for either.

    NCERT Class 11 Biology, page 11

15. Q15 Assertion and Reason

    AssertionDeuteromycetes reproduce only by asexual spores called conidia.

    ReasonOnce the sexual forms of deuteromycetes are discovered they are moved into ascomycetes or basidiomycetes.

    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 deuteromycetes; their reclassification is a parallel consequence and does not explain the restriction to conidia.

    What this is testing: whether a consequence can serve as a reason.

    A says deuteromycetes reproduce only by asexual spores called conidia. True.
    R says that once their sexual forms are discovered they are moved into ascomycetes or basidiomycetes. True.

    Both true, but R does not explain A, so the code is (2). R describes what taxonomists do afterwards; it does not say why only conidia are seen.

    The trap: R feels like it completes the story, and completeness feels like explanation. R is the result of A, not its cause — and a result placed under A is a common way to build a (2).

    NCERT Class 11 Biology, page 18

16. Q16 Assertion and Reason

    AssertionIn basidiomycetes the basidiospores are produced endogenously within the basidium.

    ReasonIn basidiomycetes four basidiospores are produced exogenously on the basidium after karyogamy and meiosis.

    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; R is true.

    What this is testing: whether basidiospores form inside or outside the basidium.

    A says basidiospores are produced endogenously within the basidium. False. They are produced EXOGENOUSLY, on the outside of the club-shaped basidium.
    R says four basidiospores are produced exogenously on the basidium after karyogamy and meiosis. True.

    A false and R true is code (4).

    The trap: endogenous belongs to the ascomycetes, where ascospores form inside the ascus. The paper has moved that word one group across. Keep the pair straight: inside the ascus, outside the basidium.

    NCERT Class 11 Biology, page 18

17. Q17 Assertion and Reason

    AssertionFungal spores are the chief means of dispersal.

    ReasonFungi are cosmopolitan and occur in air, water, soil and on animals and plants.

    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 fungi; their wide distribution is a parallel fact and does not by itself explain the role of spores in dispersal.

    What this is testing: whether wide distribution explains the role of spores.

    A says fungal spores are the chief means of dispersal. True.
    R says fungi are cosmopolitan, occurring in air, water, soil and on animals and plants. True.

    Both true, but R does not explain A, so the code is (2). R describes the result — fungi turning up everywhere — while A is about the mechanism that carries them there.

    The trap: the two lines feel joined because spreading everywhere needs a way of spreading. Read the direction. R would be explained by A, not the other way round, and that reversal is a classic (2).

    NCERT Class 11 Biology, page 16

18. Q18 Statement I and Statement II

    Statement ILichens and viruses are included in the five kingdom system.

    Statement IIViruses are non-cellular and are not considered truly living.

    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 (they are excluded); II correct.

    What this is testing: what the five kingdom system leaves out.

    Statement I: lichens and viruses are included in the five kingdom system. Incorrect. Viruses, viroids, prions and lichens are all left out of it.
    Statement II: viruses are non-cellular and are not considered truly living. Correct.

    So I is incorrect and II is correct, giving (4).

    The trap: II holds the reason I fails. The five kingdoms sort organisms by cell structure, and something with no cell of its own cannot be placed. When one statement explains why the other is impossible, trust the explaining one.

    NCERT Class 11 Biology, page 19

19. Q19 Statement I and Statement II

    Statement IThe two-kingdom system did not distinguish between prokaryotes and eukaryotes.

    Statement IIThe two-kingdom system was based only on gross morphology.

    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 weaknesses of the old two-kingdom system.

    Statement I: it did not distinguish prokaryotes from eukaryotes. Correct.
    Statement II: it was based only on gross morphology, that is, on the large features you can see from outside. Correct.

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

    The trap: II sounds like a harsh judgement rather than a fact, and harsh-sounding lines feel planted. It is the reason behind I — if you judge only by outward appearance you never reach the cell, so prokaryote and eukaryote cannot be told apart.

    NCERT Class 11 Biology, page 10

20. Q20 Statement I and Statement II

    Statement IDinoflagellates are mostly marine and photosynthetic.

    Statement IIDinoflagellates possess a protein-rich pellicle instead of a cell wall.

    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 incorrectCorrect answer
    4. 4.Statement I is incorrect but Statement II is correct

    Why option 3 is the answer

    The trap: I correct; dinoflagellates have stiff CELLULOSE PLATES, not a pellicle, so II is incorrect.

    What this is testing: what covers a dinoflagellate.

    Statement I: dinoflagellates are mostly marine and photosynthetic. Correct.
    Statement II: they have a protein-rich pellicle instead of a cell wall. Incorrect. The pellicle belongs to the EUGLENOIDS. A dinoflagellate has a stiff cell wall with cellulose plates on its outer surface.

    So I is correct and II is incorrect, giving (3).

    The trap: pellicle is a real word from the same section of the chapter, moved one group across. Fix the pair: cellulose plates for dinoflagellates, pellicle for euglenoids.

    NCERT Class 11 Biology, page 15

21. Q21 Match the columns

    Match the disease with its causal agent:

    Column I	Column II
    (a) Potato spindle tuber	(ii) virus
    (b) Mad cow disease	(iv) bacterium
    (c) Mumps	(i) viroid
    (d) Citrus canker	(iii) prion

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

    Why option 4 is the answer

    The trap: Viroid, prion, virus and bacterium as causal agents.

    What this is testing: matching a disease to the kind of agent that causes it.

    Potato spindle tuber disease is caused by a viroid. Mad cow disease is caused by a prion. Mumps is caused by a virus. Citrus canker is caused by a bacterium.

    That gives (a)-(i), (b)-(iii), (c)-(ii), (d)-(iv) — option 4.

    The trap: options 1 and 2 swap viroid with prion or with virus, and those three words look alike at speed. Fix the two odd ones: potato goes with viroid, cattle go with prion. Whatever is left over is the ordinary virus and the ordinary bacterium.

    NCERT Class 11 Biology, page 20

22. Q22 Match the columns

    Match the kingdom with its mode of nutrition (Table 2.1):

    Column I	Column II
    (a) Monera	(i) heterotrophic (saprophytic/parasitic)
    (b) Fungi	(ii) heterotrophic (holozoic)
    (c) Plantae	(iii) autotrophic and heterotrophic
    (d) Animalia	(iv) autotrophic

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

    Why option 3 is the answer

    The trap: Monera-both, Fungi-saprophytic/parasitic, Plantae-autotrophic, Animalia-holozoic.

    What this is testing: the nutrition column of the five kingdom table.

    Monera is both autotrophic and heterotrophic. Fungi are heterotrophic, as saprophytes or parasites. Plantae is autotrophic. Animalia is heterotrophic of the holozoic type, taking food in and digesting it inside.

    That gives (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii) — option 3.

    The trap: option 2 moves the autotrophic label onto the fungi. Fungi have no chlorophyll, so they can never be autotrophic. That single fact removes two of the four options at once.

    NCERT Class 11 Biology, page 11

23. Q23 Match the columns

    Match the fungal example with its use/effect:

    Column I	Column II
    (a) Penicillium	(iv) bread and beer making
    (b) Saccharomyces	(ii) wheat rust
    (c) Puccinia	(iii) smut
    (d) Ustilago	(i) source of antibiotic

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

    Why option 1 is the answer

    The trap: Penicillium-antibiotic, Saccharomyces-yeast, Puccinia-rust, Ustilago-smut.

    What this is testing: what four named fungi are known for.

    Penicillium gives the antibiotic penicillin. Saccharomyces is the yeast used in bread and beer making. Puccinia is the wheat rust. Ustilago is the smut.

    That gives (a)-(i), (b)-(iv), (c)-(ii), (d)-(iii) — option 1.

    The trap: options 2 and 3 swap the useful pair, Penicillium with Saccharomyces, and both are indeed useful to people. Separate them by product: one gives medicine, the other gives bread and beer. Puccinia and Ustilago are the two plant diseases, rust and smut.

    NCERT Class 11 Biology, page 18

24. Q24 Match the columns

    Match the bacterial nutrition type with its description:

    Column I	Column II
    (a) Photosynthetic autotroph	(iii) the vast majority of bacteria
    (b) Chemosynthetic autotroph	(iv) recycles nutrients
    (c) Heterotroph	(ii) uses light energy
    (d) Decomposer	(i) oxidises inorganic substances

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

    Why option 3 is the answer

    The trap: Photosynthetic, chemosynthetic, heterotrophic and decomposer bacteria.

    What this is testing: the different ways bacteria feed.

    Photosynthetic autotrophs use light energy. Chemosynthetic autotrophs oxidise inorganic substances. Heterotrophs are the vast majority of bacteria. Decomposers recycle nutrients.

    That gives (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv) — option 3.

    The trap: option 1 swaps the two autotrophic lines, handing light to the chemosynthetic ones. The prefix settles it — photo means light, chemo means chemical — and no chemosynthetic bacterium needs the sun at all.

    NCERT Class 11 Biology, page 13

25. Q25 Exception / incorrect

    All are true of diatoms EXCEPT:

    1. 1.walls embedded with silica
    2. 2.cell walls made of chitinCorrect answer
    3. 3.walls are indestructible
    4. 4.chief producers in the oceans

    Why option 2 is the answer

    The trap: Chitin is a fungal wall component.

    What this is testing: what a diatom wall is made of.

    Diatom walls are embedded with silica, are indestructible because of it, and diatoms are the chief producers in the oceans. All true. The wall is not made of chitin — chitin is the FUNGAL wall material.

    So the exception is the chitin.

    The trap: the question offers two wall descriptions, silica and chitin, and only one can belong here. Keep the three wall materials apart: cellulose for plants, chitin for fungi, silica for diatoms.

    NCERT Class 11 Biology, page 14

26. Q26 Exception / incorrect

    Identify the INCORRECT statement about the five kingdom system:

    1. 1.includes viruses and lichensCorrect answer
    2. 2.proposed by Whittaker
    3. 3.proposed in 1969
    4. 4.includes Monera, Protista, Fungi, Plantae, Animalia

    Why option 1 is the answer

    The trap: Viruses, viroids, prions and lichens are excluded.

    What this is testing: what the five kingdom system does and does not contain.

    It was proposed by Whittaker, in 1969, and its kingdoms are Monera, Protista, Fungi, Plantae and Animalia. All correct. The claim that it includes viruses and lichens is false — viruses, viroids, prions and lichens are all left out.

    So the incorrect statement is the one that includes them.

    The trap: the other three options are the facts everybody revises, so the fourth slips past as another harmless detail. Remember why they are excluded — the system sorts cells, and a virus has no cell of its own.

    NCERT Class 11 Biology, page 19

27. Q27 Sequence / ordering

    Correct order of decreasing size:

    1. 1.Viroid → Virus → Bacterium
    2. 2.Virus → Bacterium → Viroid
    3. 3.Bacterium → Virus → ViroidCorrect answer
    4. 4.Bacterium → Viroid → Virus

    Why option 3 is the answer

    The trap: Viruses are smaller than bacteria; viroids are smaller than viruses.

    What this is testing: the relative sizes of a bacterium, a virus and a viroid.

    A bacterium is the largest of the three. A virus is smaller than a bacterium. A viroid is smaller than a virus. So in decreasing order it is bacterium, virus, viroid — option 3.

    The trap: option 1 gives the same list reversed, and a student who reads the question as increasing order will take it. Read the direction word before you read the options. Decreasing means starting with the biggest, and the only cellular organism here is the bacterium.

    NCERT Class 11 Biology, page 21

28. Q28 NEET 2025

    Correct order of increasing complexity of body organisation:

    1. 1.Eukaryotes with cellular organisation → Prokaryotes → Multicellular heterotrophs → Eukaryotic autotrophs → Heterotrophs with organ systems
    2. 2.Prokaryotes with a cell wall of polysaccharides/amino acids → Eukaryotes with cellular organisation → Multicellular heterotrophs with a chitin cell wall → Eukaryotic autotrophs with tissue/organ level → Heterotrophs with tissue/organ/organ-system levelCorrect answer
    3. 3.Prokaryotes → Multicellular heterotrophs → Eukaryotes → Heterotrophs with organ systems → Eukaryotic autotrophs
    4. 4.Multicellular heterotrophs → Prokaryotes → Eukaryotes → Eukaryotic autotrophs → Heterotrophs with organ systems

    Why option 2 is the answer

    The trap: This traces Monera → Protista → Fungi → Plantae → Animalia, in increasing order of body-organisation complexity.

    What this is testing: the order of the five kingdoms by complexity of body organisation.

    Option 2 runs prokaryotes with a wall of polysaccharides and amino acids, then eukaryotes at the cellular level, then multicellular heterotrophs with a chitin wall, then eukaryotic autotrophs with tissues and organs, then heterotrophs reaching organ-system level. That is Monera, Protista, Fungi, Plantae, Animalia.

    Why the others are wrong: options 1 and 4 do not start with the prokaryotes, and nothing can be simpler than a cell with no nucleus. Option 3 places multicellular heterotrophs before single-celled eukaryotes.

    The trap: check the first item alone. Monera must lead, and that kills two options at once.

    NCERT Class 11 Biology, pages 11-19

29. Q29 NEET 2020

    Which is correct about viroids?

    1. 1.DNA with a protein coat
    2. 2.Free DNA without a protein coat
    3. 3.RNA with a protein coat
    4. 4.Free RNA without a protein coatCorrect answer

    Why option 4 is the answer

    The trap: Viroids are free RNA molecules with no protective protein coat.

    What this is testing: what a viroid is, in one line.

    Free RNA without a protein coat. That is the whole description — RNA of low molecular weight, naked.

    Why the others are wrong: the two DNA options come from the habit of equating genetic material with DNA, and a viroid has no DNA. 'RNA with a protein coat' is the sharpest trap, because it gets the nucleic acid right and then adds the very thing a viroid lacks. That coat is what makes something a virus.

    The trap: half-right options feel safer than they are. Check both halves — the nucleic acid and the coat — before choosing.

    NCERT Class 11 Biology, page 21

30. Q30 NEET 2017

    Viroids differ from viruses in having:

    1. 1.DNA molecules without a protein coat
    2. 2.RNA molecules with a protein coat
    3. 3.RNA molecules without a protein coatCorrect answer
    4. 4.DNA molecules with a protein coat

    Why option 3 is the answer

    The trap: Viroids are free RNA molecules lacking the protein coat that viruses possess.

    What this is testing: the single difference between a viroid and a virus.

    Viroids are RNA molecules with no protein coat. A virus has its nucleic acid wrapped in a capsid; a viroid goes without one.

    Why the others are wrong: the two DNA options fail at the first step, since viroid genetic material is RNA, never DNA. 'RNA with a protein coat' is the sharpest trap — it gets the nucleic acid right and then gives back the coat, which describes a virus, exactly the thing the question asks you to distinguish.

    The trap: both halves of the option must be right. Check the nucleic acid, then check the coat.

    NCERT Class 11 Biology, page 21