Biological Classification Full Chapter in 1 Hour | NCERT Biology Line By Line | NEET 2027 Biology |

 

📘 Biological Classification – NCERT Ch-2 (Full in Points + PYQ Tags)

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1. History of Classification

• Since civilisation → humans classified organisms for food, shelter, clothing.

• Aristotle:

• Plants → herbs, shrubs, trees.

• Animals → with red blood / without red blood.

• Linnaeus (2-kingdom system): Plantae & Animalia.

• Problems:

• Prokaryotes & eukaryotes not separated.

• Unicellular & multicellular kept together.

• Algae (autotrophic) & fungi (heterotrophic) together.

• Whittaker (1969): Five Kingdoms

• Monera, Protista, Fungi, Plantae, Animalia.

• Criteria: cell structure, body organisation, nutrition, reproduction, phylogeny. 👉 [NEET PYQ]

2. Kingdom Monera

• Includes bacteria + mycoplasma.

• Ubiquitous → soil, water, air, extreme habitats, parasites.

• Shapes: cocci, bacilli, spirilla, vibrio. 👉 [NEET PYQ]

• Nutrition: autotrophs (photo-, chemo-), heterotrophs.

2.1 Archaebacteria

• Special cell wall (no peptidoglycan).

• Survive extremes.

• Types:

• Halophiles → salty areas. 👉 [NEET PYQ]

• Thermoacidophiles → hot springs.

• Methanogens → swamps, cattle rumen → produce methane (biogas). 👉 [NEET PYQ]

2.2 Eubacteria

• Rigid cell wall, flagellated.

• Cyanobacteria (blue-green algae):

• Chlorophyll a, photosynthetic autotrophs.

• Unicellular/colonial/filamentous.

• Surrounded by gelatinous sheath.

• Form blooms in polluted water. 👉 [NEET PYQ]

• Nitrogen fixation in heterocysts → Nostoc, Anabaena. 👉 [NEET PYQ]

• Chemosynthetic bacteria: oxidise nitrite, nitrate, ammonia → recycle nutrients. 👉 [NEET PYQ]

• Heterotrophic bacteria:

• Decomposers.

• Useful → curd (Lactobacillus), antibiotics, nitrogen fixation. 👉 [NEET PYQ]

• Harmful → cholera, typhoid, tetanus, citrus canker. 👉 [NEET PYQ]

• Reproduction: Binary fission, spores, primitive DNA transfer (conjugation). 👉 [NEET PYQ]

2.3 Mycoplasma

• No cell wall.

• Smallest living cell. 👉 [NEET PYQ]

• Survive without oxygen.

• Pathogenic.

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3. Kingdom Protista

• All unicellular eukaryotes.

• Aquatic.

• Link between plants, animals, fungi.

• Reproduction: asexual (binary fission), sexual (zygote).

Groups

1. Chrysophytes (Diatoms, Desmids)
   
   

• Microscopic, planktonic.

• Silica wall → indestructible, soap-box fitting. 👉 [NEET PYQ]

• Accumulation → diatomaceous earth → polishing, filtration. 👉 [NEET PYQ]

• Chief producers of ocean. 👉 [NEET PYQ]

2. Dinoflagellates
   
   

• Marine, photosynthetic.

• Pigments → yellow, red, brown, green.

• Cell wall → cellulose plates.

• 2 flagella → longitudinal & transverse.

• Example: Gonyaulax → red tides, release toxins, kill fish. 👉 [NEET PYQ]

3. Euglenoids
   
   

• Freshwater, stagnant water.

• Protein layer pellicle (flexible).

• Dual nutrition → autotroph (light), heterotroph (dark). 👉 [NEET PYQ]

• Example: Euglena.

4. Slime Moulds
   
   

• Saprophytic.

• Body → plasmodium (multinucleate).

• Unfavourable condition → fruiting bodies with spores.

• Spores resistant & dispersed by air. 👉 [NEET PYQ]

5. Protozoa
   
   

• All heterotrophs.

• Types:

• Amoeboids → pseudopodia (Amoeba, Entamoeba). 👉 [NEET PYQ]

• Flagellates → Trypanosoma (sleeping sickness). 👉 [NEET PYQ]

• Ciliates → Paramoecium (gullet, cilia). 👉 [NEET PYQ]

• Sporozoans → Plasmodium (malaria). 👉 [NEET PYQ]

4. Kingdom Fungi

• Eukaryotic, heterotrophic.

• Cell wall = chitin.

• Body → hyphae; network = mycelium.

• Hyphae → coenocytic or septate.

• Nutrition → saprophytes, parasites, symbionts (lichens, mycorrhiza).

• Reproduction:

• Vegetative → fragmentation, fission, budding.

• Asexual → spores (conidia, sporangiospores, zoospores). 👉 [NEET PYQ]

• Sexual → plasmogamy → karyogamy → meiosis → haploid spores. 👉 [NEET PYQ]

• Dikaryon stage in Ascomycetes & Basidiomycetes. 👉 [NEET PYQ]

Classes

1. Phycomycetes → aquatic, decaying wood, obligate parasites.
   
   

• Asexual → zoospores/aplanospores.

• Sexual → zygospore.

• Examples: Rhizopus (bread mould), Mucor, Albugo. 👉 [NEET PYQ]

2. Ascomycetes (Sac fungi) → septate mycelium.
   
   

• Asexual → conidia (exogenous).

• Sexual → ascospores (endogenous, in asci).

• Examples: Yeast (unicellular), Penicillium, Neurospora, morels, truffles. 👉 [NEET PYQ]

3. Basidiomycetes → mushrooms, smuts, rusts.
   
   

• Mycelium septate.

• Sex organs absent; plasmogamy via somatic fusion.

• Spores → basidiospores on basidium.

• Examples: Agaricus (mushroom), Puccinia (wheat rust), Ustilago (smut). 👉 [NEET PYQ]

4. Deuteromycetes (Imperfect fungi)
   
   

• Only asexual stage known (conidia).

• Saprophytes, parasites, decomposers.

• Examples: Alternaria, Colletotrichum, Trichoderma. 👉 [NEET PYQ]

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5. Kingdom Plantae

• Eukaryotic, chlorophyll, photosynthetic.

• Cell wall = cellulose.

• Few heterotrophic → Cuscuta (parasite), Bladderwort, Venus flytrap (insectivorous). 👉 [NEET PYQ]

• Groups → algae, bryophytes, pteridophytes, gymnosperms, angiosperms.

• Life cycle → alternation of generations (sporophyte ↔ gametophyte). 👉 [NEET PYQ]

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6. Kingdom Animalia

• Eukaryotic, multicellular, heterotrophic.

• No cell wall.

• Nutrition → holozoic.

• Growth definite, locomotion present.

• Reproduction sexual (male + female gametes, embryonic development). 👉 [NEET PYQ]

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7. Viruses, Viroids, Prions, Lichens

• Viruses
  
  

• Acellular, nucleoprotein.

• Outside host → inert crystal. 👉 [NEET PYQ]

• Genetic material:

• Plant viruses → ssRNA.

• Animal viruses → ss/dsRNA or dsDNA.

• Bacteriophages → dsDNA. 👉 [NEET PYQ]

• Examples: TMV, bacteriophage, HIV, influenza, smallpox, herpes. 👉 [NEET PYQ]

• Viroids
  
  

• Discovered by T.O. Diener (1971).

• Free RNA, no protein coat. 👉 [NEET PYQ]

• Example: Potato spindle tuber disease.

• Prions
  
  

• Infectious proteins, abnormal folding.

• Cause neurological diseases.

• Examples: Mad cow disease (BSE), CJD. 👉 [NEET PYQ]

• Lichens
  
  

• Symbiosis of algae (phycobiont) + fungi (mycobiont).

• Algae → food; fungi → shelter, minerals, water.

• Pollution indicators. 👉 [NEET PYQ]

📝 NEET Mega Question Bank – Biological Classification (90 Qs)

(A) General Classification (1–15)

1. Who proposed the five-kingdom system of classification?
A) Linnaeus B) Whittaker C) Aristotle D) Haeckel

2. The main criteria used by Whittaker for classification included:
A) Cell structure, body organization, nutrition, reproduction, phylogeny
B) Locomotion, shape, body size, color
C) Habitat, symmetry, coelom, development
D) None of these

3. Which was the major drawback of the two-kingdom system of classification?
A) Viruses ignored B) Prokaryotes not separated C) Fungi with plants D) All of these

4. In three-domain system, Monera is split into:
   A) Plantae & Animalia B) Protista & Fungi C) Archaea & Bacteria D) Virus & Viroid
   
   

5. Which kingdom includes prokaryotes?
   A) Protista B) Monera C) Plantae D) Fungi
   
   

6. Plantae + Animalia system was proposed by:
   A) Linnaeus B) Haeckel C) Aristotle D) Whittaker
   
   

7. Which scientist classified plants into herbs, shrubs, and trees?
   A) Whittaker B) Aristotle C) Linnaeus D) Darwin
   
   

8. Which system wrongly grouped fungi with plants?
A) Two kingdom B) Five kingdom C) Three domain D) Six kingdom

9. Cell wall of fungi is made up of:
   A) Cellulose B) Chitin C) Peptidoglycan D) Silica

10. Alternation of generations occurs in:
A) Animals B) Plants C) Protists D) Monera

11. The basis of modern classification is mainly:
    A) Morphology B) Phylogeny C) Habitat D) Nutrition
    
    

12. Which scientist introduced the term Protista?
    A) Whittaker B) Haeckel C) Linnaeus D) Aristotle
    
    

13. Who divided animals into those having red blood and those not?
    A) Darwin B) Whittaker C) Aristotle D) Linnaeus
    
    

14. Which group is not included in five-kingdom classification?
    A) Monera B) Protista C) Viruses D) Fungi
    
    

15. Which of the following kingdoms has organisms without a true nucleus?
    A) Protista B) Monera C) Plantae D) Fungi

(B) Kingdom Monera (16–30)

16. Bacteria without cell wall are called:
A) Archaebacteria B) Mycoplasma C) Cyanobacteria D) Eubacteria

17. Methanogens are commonly found in:
A) Hot springs B) Salty lakes C) Rumen of cattle D) Human intestine

18. Which of the following is NOT an Archaebacteria?
    A) Halophiles B) Thermoacidophiles C) Methanogens D) Nostoc

19. Nostoc fixes nitrogen in specialized cells called:
A) Vegetative cell B) Heterocyst C) Endospore D) Capsule

20. Chemosynthetic autotrophic bacteria obtain energy from:
    A) Organic compounds B) Inorganic substances C) Sunlight D) Oxygen

21. Citrus canker is caused by:
A) Virus B) Fungus C) Bacterium D) Viroid

22. Lactobacillus helps in:
    A) Antibiotics B) Curd formation C) Nitrogen fixation D) Biogas production
    
    

23. Bacillus shape is:
    A) Spherical B) Rod-shaped C) Spiral D) Comma
    
    

24. Which bacteria oxidize ammonia to nitrite?
    A) Nitrosomonas B) Nitrobacter C) Rhizobium D) Azotobacter
    
    

25. Which bacteria are used in sewage treatment?
    A) Methanogens B) Cyanobacteria C) Mycoplasma D) Lactobacillus
    
    

26. Blue-green algae are also called:
    A) Eubacteria B) Cyanobacteria C) Archaebacteria D) Mycoplasma
    
    

27. Which bacteria form endospores under unfavorable conditions?
    A) Mycoplasma B) Bacillus C) Lactobacillus D) Nostoc
    
    

28. Smallest living cell without cell wall is:
    A) Virus B) Viroid C) Mycoplasma D) Rhizobium
    
    

29. Which group of bacteria are natural decomposers?
    A) Cyanobacteria B) Heterotrophic bacteria C) Archaebacteria D) Mycoplasma
    
    

30. Which disease is caused by bacteria?
    A) Malaria B) Typhoid C) AIDS D) Ringworm

(C) Kingdom Protista (31–45)

31. The cell wall of diatoms is composed of:
A) Cellulose B) Chitin C) Silica D) Lignin

32. Red tides in oceans are caused by:
A) Euglena B) Gonyaulax C) Nostoc D) Diatoms

33. The chief producers of oceans are:
A) Dinoflagellates B) Diatoms C) Protozoa D) Slime moulds

34. Euglenoids have:
A) Cellulose wall B) Protein pellicle C) Chitin wall D) Silica wall

35. Plasmodium belongs to:
A) Sporozoans B) Flagellates C) Amoeboids D) Ciliates

36. Trypanosoma causes:
    A) Sleeping sickness B) Malaria C) Amoebiasis D) Kala azar
    
    

37. Amoeboids move by:
    A) Flagella B) Cilia C) Pseudopodia D) None
    
    

38. Ciliates show coordinated movement of:
    A) Flagella B) Pseudopodia C) Cilia D) Sporozoites
    
    

39. Diatomaceous earth is used in:
    A) Polishing B) Brewing C) Cheese making D) Curdling
    
    

40. Slime mould body is called:
    A) Sporangium B) Plasmodium C) Mycelium D) Ascocarp
    
    

41. Which protist is both autotrophic and heterotrophic?
    A) Amoeba B) Euglena C) Paramoecium D) Plasmodium
    
    

42. Dinoflagellates typically have how many flagella?
    A) One B) Two C) Three D) Four
    
    

43. Which protozoan is responsible for amoebic dysentery?
    A) Entamoeba histolytica B) Plasmodium C) Paramoecium D) Trypanosoma
    
    

44. The gullet is present in:
    A) Euglena B) Plasmodium C) Paramoecium D) Amoeba
    
    

45. Slime mould spores are dispersed by:
    A) Water B) Wind C) Animals D) Insects

(D) Kingdom Fungi (46–60)

46. Bread mould is:
A) Mucor B) Rhizopus C) Puccinia D) Neurospora

47. Penicillium belongs to:
A) Basidiomycetes B) Ascomycetes C) Phycomycetes D) Deuteromycetes

48. Dikaryon stage occurs in:
A) Ascomycetes & Basidiomycetes B) Phycomycetes C) Deuteromycetes D) All fungi

49. Asexual spores in Ascomycetes are:
    A) Zoospores B) Conidia C) Basidiospores D) Oospores
    
    

50. Neurospora is widely used in:
    A) Antibiotics B) Genetic studies C) Brewing D) Cheese making
    
    

51. Puccinia is a parasite that causes:
A) Rust of wheat B) Smut C) Citrus canker D) White rust

52. Mushroom (Agaricus) belongs to:
    A) Ascomycetes B) Basidiomycetes C) Phycomycetes D) Deuteromycetes
    
    

53. Morels and truffles are:
    A) Ascomycetes B) Basidiomycetes C) Deuteromycetes D) Phycomycetes
    
    

54. Imperfect fungi are so called because:
    A) No asexual stage B) No sexual stage C) No spores D) No mycelium
    
    

55. Fungi in mycorrhiza are:
    A) Saprophytes B) Symbionts C) Parasites D) None
    
    

56. White rust of mustard is caused by:
    A) Albugo B) Puccinia C) Rhizopus D) Ustilago
    
    

57. Common edible mushroom is:
    A) Agaricus B) Puccinia C) Penicillium D) Rhizopus
    
    

58. Sexual reproduction in fungi involves:
    A) Plasmogamy → Karyogamy → Meiosis B) Meiosis → Karyogamy → Plasmogamy C) Karyogamy → Plasmogamy → Meiosis D) Mitosis only
    
    

59. Cell wall of fungi is made of:
    A) Cellulose B) Chitin C) Silica D) Pectin
    
    

60. Which fungus is used for alcohol production?
    A) Yeast B) Penicillium C) Rhizopus D) Aspergillus

(E) Plantae (61–70)

61. Example of an insectivorous plant is:
A) Cuscuta B) Venus flytrap C) Nostoc D) Ficus

62. Example of a parasitic plant is:
A) Cuscuta B) Rhizopus C) Venus flytrap D) Agaricus

63. Alternation of generation means:
A) Sporophyte alternates with gametophyte B) Sporophyte alternates with zygote C) Gamete alternates with zygote D) None

64. Sporophyte is:
A) Diploid B) Haploid C) Triploid D) None

65. Gametophyte is:
A) Diploid B) Haploid C) Polyploid D) None

66. Reserve food in plants is:
    A) Starch B) Glycogen C) Protein D) Fat
    
    

67. Cell wall of plants is made of:
    A) Chitin B) Cellulose C) Silica D) Peptidoglycan
    
    

68. Example of a bryophyte is:
    A) Moss B) Fern C) Pine D) Mango
    
    

69. Example of a gymnosperm is:
    A) Mango B) Pinus C) Fern D) Moss
    
    

70. Example of an angiosperm is:
    A) Mango B) Moss C) Cycas D) Fern

(F) Animalia (71–80)

71. Animals are:
A) Autotrophic B) Heterotrophic C) Mixotrophic D) Chemotrophic

72. Reserve food in animals is:
A) Starch B) Glycogen C) Cellulose D) Protein

73. Nutrition in animals is:
A) Saprophytic B) Holozoic C) Parasitic D) Autotrophic

74. Animals lack:
A) Cell wall B) Mitochondria C) Ribosome D) Nucleus

75. In animals, growth is:
    A) Indefinite B) Definite C) Fragmented D) None
    
    

76. Animals store food as:
    A) Starch B) Glycogen & Fat C) Protein D) Cellulose
    
    

77. Fertilization in higher animals is usually:
    A) External B) Internal C) Asexual D) None
    
    

78. Which of the following is absent in all animals?
    A) Chloroplast B) Cell wall C) Both A and B D) Nucleus
    
    

79. Advanced animals show:
    A) Sensory & neuromotor system B) Cell wall C) Photosynthesis D) Spore formation
    
    

80. Mode of reproduction in animals is:
    A) Asexual B) Sexual C) Budding D) Spore
    
    

(G) Viruses, Viroids, Prions, Lichens (81–90)

81. Viruses are:
A) Cellular B) Acellular C) Multicellular D) None

82. Genetic material in plant viruses is:
A) DNA B) RNA C) Protein D) None

83. Genetic material in bacteriophages is:
A) dsDNA B) ssRNA C) dsRNA D) Protein

84. TMV was crystallized by:
    A) Stanley B) Diener C) Ivanowsky D) Pasteur

85. Viroids were discovered by:
A) Diener B) Stanley C) Ivanowsky D) Beijerinck

86. Potato spindle tuber disease is caused by:
    A) Viroid B) Virus C) Prion D) Fungus
    
    

87. Prions are:
    A) Proteins only B) DNA only C) RNA only D) DNA + RNA
    
    

88. Mad cow disease is caused by:
    A) Virus B) Prion C) Fungus D) Bacterium
    
    

89. Lichen is a symbiotic association between:
A) Fungus + Alga B) Fungus + Bacteria C) Alga + Virus D) Fungus + Protozoa

90. Lichens are considered indicators of:
A) Soil fertility B) Water purity C) Air pollution D) Light intensity

✅ Answer Key (1–90)

1-B, 2-A, 3-D, 4-C, 5-B, 6-A, 7-B, 8-A, 9-B, 10-B, 11-B, 12-B, 13-C, 14-C, 15-B,
16-B, 17-C, 18-D, 19-B, 20-B, 21-C, 22-B, 23-B, 24-A, 25-A, 26-B, 27-B, 28-C, 29-B, 30-B,
31-C, 32-B, 33-B, 34-B, 35-A, 36-A, 37-C, 38-C, 39-A, 40-B, 41-B, 42-B, 43-A, 44-C, 45-B,
46-B, 47-B, 48-A, 49-B, 50-B, 51-A, 52-B, 53-A, 54-B, 55-B, 56-A, 57-A, 58-A, 59-B, 60-A,
61-B, 62-A, 63-A, 64-A, 65-B, 66-A, 67-B, 68-A, 69-B, 70-A,
71-B, 72-B, 73-B, 74-A, 75-B, 76-B, 77-B, 78-C, 79-A, 80-B,
81-B, 82-B, 83-A, 84-A, 85-A, 86-A, 87-A, 88-B, 89-A, 90-C.