Structural Organisation in Animals | PART 9 | CLASS 11th BIOLOGY | NEET 2027 | NCERT Line by Line

Chapter 7 – Structural Organisation in Animals (NCERT Notes + Hinglish Tricks)

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🌿 Introduction

• Unicellular organisms → all life functions (digestion, respiration, reproduction) by single cell.

• Multicellular organisms → functions divided among groups of specialised cells = tissues.

• Complex animals = 4 basic tissues: Epithelial, Connective, Muscular, Neural.

• Tissues → Organ → Organ systems.

• Division of labour ensures survival.

👉 Trick:
“ECMN” → Epithelial, Connective, Muscular, Neural (4 basic tissues).

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7.1 ORGAN AND ORGAN SYSTEM ⭐(PYQ)

• Organs = different tissues arranged in specific proportion/pattern.

• Example: Heart → all 4 tissue types.

• Organ systems = 2+ organs with common function (e.g., digestive, respiratory).

• Complexity trend = evolutionary trend.

👉 Trick:
“Heart = 4 tissues, Systems = teamwork.”

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7.2 FROGS ⭐(PYQ – Morphology + Anatomy of Frog)

• Belong to Class Amphibia, Phylum Chordata.

• Common Indian species: Rana tigrina.

• Cold-blooded (poikilotherms): body temperature varies with environment.

• Show camouflage (mimicry) → colour change for protection.

• Avoid extremes:

• Aestivation = summer sleep.

• Hibernation = winter sleep.

👉 Trick:
“Rana tigrina – mimicry master, dozes in heat/cold.”

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7.2.1 Morphology of Frog

• Skin: smooth, moist (mucus), thin, vascular → respiration.

• Dorsal side: olive green + dark spots.

• Ventral side: pale yellow.

• Frog absorbs water through skin (never drinks).

• Body: Head + Trunk (no neck, no tail).

• Head:

• Nostrils above mouth.

• Eyes: bulging, nictitating membrane (protects under water).

• Tympanum (ear) → sound reception.

• Limbs:

• Forelimbs (4 digits) → support.

• Hindlimbs (5 digits, muscular, webbed) → swimming, leaping, burrowing.

• Sexual dimorphism:

• Males → vocal sacs + copulatory pads (on forelimb first digit).

👉 Trick:
“4 fore, 5 hind, Males sing & hug.”

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7.2.2 Anatomy of Frog

Digestive System ⭐(PYQ)

• Short alimentary canal (carnivorous diet).

• Mouth → buccal cavity → pharynx → oesophagus → stomach → intestine → rectum → cloaca.

• Glands:

• Liver → bile (stored in gall bladder).

• Pancreas → pancreatic juice.

• Tongue: bilobed, sticky → captures food.

• Stomach: HCl + gastric juice → chyme.

• Duodenum: bile (fat emulsification) + pancreatic juice (digest protein, carb).

• Intestine: final digestion + absorption (via villi, microvilli).

• Rectum → Cloaca → outside.

👉 Trick:
“Liver bile, Pancreas juice, Tongue trap.”

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Respiration ⭐(PYQ)

• Aquatic (cutaneous): via skin (diffusion).

• Terrestrial (pulmonary): lungs + skin + buccal cavity.

• During hibernation/aestivation: cutaneous only.

• Lungs: paired, pink, sac-like.

👉 Trick:
“Water → Skin, Land → Lung + Skin + Buccal.”

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Circulatory System ⭐(PYQ)

• Closed type.

• Heart: 3 chambers (2 atria + 1 ventricle).

• Covered by pericardium.

• Sinus venosus → right atrium.

• Ventricle → conus arteriosus.

• Blood: plasma + cells.

• RBCs nucleated, haemoglobin present.

• Portal systems:

• Hepatic portal (intestine → liver).

• Renal portal (lower body → kidney).

• Lymphatic system also present.

👉 Trick:
“2 atria + 1 ventricle = Amphibian heart.”

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Excretory System ⭐(PYQ)

• Paired kidneys (dark red, bean-shaped).

• Made of nephrons.

• Ureters:

• Male → urinogenital duct (open in cloaca).

• Female → separate opening in cloaca.

• Urinary bladder → cloaca.

• Excretion: Ureotelic (urea).

👉 Trick:
“Kidney → Ureter → Cloaca, Frog = Ureotelic.”

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Nervous & Endocrine System ⭐(PYQ)

• Nervous system:

• CNS: brain + spinal cord.

• PNS: cranial (10 pairs) + spinal nerves.

• ANS: sympathetic + parasympathetic.

• Brain box = cranium.

• Brain divisions:

• Forebrain: olfactory lobes, cerebral hemispheres, diencephalon.

• Midbrain: optic lobes.

• Hindbrain: cerebellum + medulla oblongata.

• Endocrine glands: Pituitary, Thyroid, Parathyroid, Thymus, Pineal, Adrenal, Pancreatic islets, Gonads.

👉 Trick:
“F-M-H (Fore, Mid, Hind) = Frog brain map.”

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Sense Organs

• Touch → sensory papillae.

• Taste → taste buds.

• Smell → nasal epithelium.

• Vision → eyes (simple eyes, nictitating membrane).

• Hearing + equilibrium → tympanum + internal ear.

👉 Trick:
“TTSVH = Touch, Taste, Smell, Vision, Hearing.”

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Reproductive System ⭐(PYQ)

• Male:

• Testes (yellow, ovoid), attached to kidney by mesorchium.

• Vasa efferentia (10–12) → kidney → Bidder’s canal → urinogenital duct → cloaca.

• Female:

• Ovaries near kidneys, oviducts → cloaca.

• Fertilisation external, in water.

• Eggs: 2500–3000 at once.

• Development via tadpole larva → metamorphosis → adult.

👉 Trick:
“Male = Testis + Mesorchium + Cloaca; Female = 3000 eggs → Tadpole.”

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Economic & Ecological Role of Frogs

• Eat insects → protect crops.

• Link in food chain/web.

• In some countries → frog legs as food.

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🐸 100 NEET MCQs – Chapter 7: Structural Organisation in Animals

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Tissues (Q1–Q20)

1. Which is the basic unit of tissue organisation?
   A. Cells B. Tissues C. Organs D. Organ systems
   
   

2. Epithelial tissue rests on:
   A. Muscle layer B. Basement membrane C. Connective tissue D. Cartilage
   
   

3. Which epithelial tissue has cilia?
   A. Cuboidal B. Columnar C. Ciliated columnar D. Squamous
   
   

4. Keratinised epithelium is found in:
   A. Skin B. Kidney C. Intestine D. Pancreas
   
   

5. Compound epithelium is mainly for:
   A. Absorption B. Protection C. Secretion D. Conduction
   
   

6. Connective tissue includes all except:
   A. Bone B. Cartilage C. Blood D. Epithelium
   
   

7. Cells of cartilage are called:
   A. Chondrocytes B. Osteocytes C. Erythrocytes D. Platelets
   
   

8. Lacunae are present in:
   A. Bone only B. Cartilage only C. Bone and cartilage D. Muscle
   
   

9. Bone matrix is rich in:
   A. Calcium salts & collagen B. Chitin C. Cellulose D. Pectin
   
   

10. Tendons connect:
    A. Muscle to bone B. Bone to bone C. Muscle to muscle D. Organ to organ
    
    

11. Ligaments connect:
    A. Muscle to bone B. Bone to bone C. Muscle to muscle D. Organ to organ
    
    

12. Adipose tissue stores:
    A. Protein B. Fat C. Minerals D. Carbohydrates
    
    

13. Blood is a:
    A. Connective tissue B. Epithelial tissue C. Muscular tissue D. Nervous tissue
    
    

14. Plasma is:
    A. Solid B. Liquid matrix C. Protein D. Hormone
    
    

15. Which cells are biconcave and without nucleus in mammals?
    A. WBC B. Platelets C. RBC D. Neutrophils
    
    

16. Muscular tissue is made of:
    A. Actin + Myosin filaments B. Keratin C. Collagen D. Elastin
    
    

17. Intercalated discs are characteristic of:
    A. Smooth muscle B. Skeletal muscle C. Cardiac muscle D. Voluntary muscle
    
    

18. Smooth muscles are:
    A. Voluntary B. Involuntary, non-striated C. Involuntary, striated D. Voluntary, striated
    
    

19. Nervous tissue functional unit:
    A. Nephron B. Neuron C. Axon D. Synapse
    
    

20. Neuroglia provide:
    A. Support & protection B. Impulses C. Hormones D. Myelin only
    
    

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Frog Morphology (Q21–Q40)

21. Scientific name of Indian frog:
    A. Bufo bufo B. Rana tigrina C. Hyla D. Rana hexadactyla
    
    

22. Frog belongs to:
    A. Pisces B. Amphibia C. Reptilia D. Mammalia
    
    

23. Frog’s skin is:
    A. Dry & scaly B. Moist & glandular C. Keratinised D. Cornified
    
    

24. Nictitating membrane covers:
    A. Nose B. Eye C. Ear D. Cloaca
    
    

25. Tympanum is for:
    A. Respiration B. Vision C. Hearing D. Digestion
    
    

26. Frogs absorb water through:
    A. Mouth B. Skin C. Intestine D. Urinary bladder
    
    

27. Hindlimbs have:
    A. 4 digits B. 5 digits (webbed) C. 3 digits D. 2 digits
    
    

28. Forelimbs have:
    A. 3 digits B. 4 digits C. 5 digits D. 6 digits
    
    

29. Sexual dimorphism in frogs is seen as:
    A. Longer hindlimbs in males B. Vocal sacs in males C. Copulatory pads in males D. Both B & C
    
    

30. Aestivation is:
    A. Winter sleep B. Summer sleep C. Day sleep D. Torpor
    
    

31. Hibernation occurs in:
    A. Summer B. Winter C. Spring D. Autumn
    
    

32. Colour change in frog is for:
    A. Breeding B. Protection (camouflage) C. Excretion D. Respiration
    
    

33. Frogs are:
    A. Warm-blooded B. Cold-blooded C. Endotherms D. Homeotherms
    
    

34. Male frog reproductive feature:
    A. Testis with mesorchium B. Ovaries near kidney C. Oviducts present D. Large eggs
    
    

35. Female frog reproductive feature:
    A. Testis B. Ovaries near kidney C. Cloacal copulatory pads D. Vocal sacs
    
    

36. Eggs laid by frog:
    A. 100 B. 500 C. 2500–3000 D. 10,000+
    
    

37. Development in frogs is via:
    A. Direct B. Indirect with larva C. Budding D. Binary fission
    
    

38. Larva of frog is called:
    A. Nymph B. Caterpillar C. Tadpole D. Planula
    
    

39. Frog’s habitat is:
    A. Only aquatic B. Only terrestrial C. Amphibious (land & water) D. Arboreal
    
    

40. Frogs maintain body temperature by:
    A. Homeothermy B. Poikilothermy C. Warm-bloodedness D. Thermoregulation
    
    

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Frog Anatomy – Systems (Q41–Q80)

41. Alimentary canal of frog opens into:
    A. Anus B. Cloaca C. Rectum D. Bladder
    
    

42. Tongue of frog is:
    A. Short & non-muscular B. Long, bifid, sticky C. Absent D. Rigid
    
    

43. Frogs are:
    A. Herbivorous B. Omnivorous C. Carnivorous D. Detritivorous
    
    

44. Liver secretes:
    A. Gastric juice B. Bile C. Mucus D. Pancreatic juice
    
    

45. Gall bladder stores:
    A. Gastric juice B. Pancreatic juice C. Bile D. Mucus
    
    

46. Pancreas secretes:
    A. Insulin only B. Pancreatic juice C. Bile D. Gastric juice
    
    

47. Final digestion & absorption occurs in:
    A. Stomach B. Intestine C. Cloaca D. Buccal cavity
    
    

48. Frog lung type:
    A. Sac-like, pink B. Lobed, spongy C. Large & multilobed D. Absent
    
    

49. Respiration in frog occurs by:
    A. Skin only B. Skin + lungs + buccal cavity C. Lungs only D. Gills
    
    

50. During hibernation, respiration is:
    A. Cutaneous only B. Pulmonary only C. Buccal only D. None
    
    

51. Heart of frog has:
    A. 2 chambers B. 3 chambers (2 atria + 1 ventricle) C. 4 chambers D. 1 chamber
    
    

52. Covering of frog heart:
    A. Pleura B. Pericardium C. Peritoneum D. Myocardium
    
    

53. Sinus venosus pours blood into:
    A. Right atrium B. Left atrium C. Ventricle D. Conus arteriosus
    
    

54. Conus arteriosus arises from:
    A. Left atrium B. Right atrium C. Ventricle D. Sinus venosus
    
    

55. Frog RBCs are:
    A. Enucleated B. Nucleated C. Anucleate biconcave D. None
    
    

56. Portal system present in frogs is:
    A. Hepatic portal B. Renal portal C. Both D. None
    
    

57. Frog kidneys are:
    A. Yellow, bean-shaped B. Red, bean-shaped C. Dark red, elongated D. Green
    
    

58. Excretion type in frogs:
    A. Uricotelic B. Ammonotelic C. Ureotelic D. None
    
    

59. Male frog ureters open into:
    A. Cloaca separately B. Urinogenital duct C. Bladder only D. Kidneys
    
    

60. Female frog ureters open into:
    A. Urinogenital duct B. Cloaca separately C. Ovaries D. Bladder
    
    

61. Brain of frog is protected by:
    A. Cranium B. Skull bones C. Vertebrae D. Cartilage
    
    

62. Frog brain – forebrain includes:
    A. Optic lobes B. Olfactory lobes + cerebrum + diencephalon C. Cerebellum D. Medulla
    
    

63. Midbrain includes:
    A. Olfactory lobes B. Optic lobes C. Cerebrum D. Cerebellum
    
    

64. Hindbrain includes:
    A. Medulla + cerebellum B. Cerebrum C. Optic lobes D. Diencephalon
    
    

65. Cranial nerves in frog:
    A. 8 pairs B. 10 pairs C. 12 pairs D. 31 pairs
    
    

66. Frog endocrine glands include:
    A. Pituitary + Thyroid + Adrenal + Gonads etc. B. Only pituitary C. Only gonads D. None
    
    

67. Frog’s sense organ for touch:
    A. Taste buds B. Sensory papillae C. Tympanum D. Olfactory epithelium
    
    

68. Frog’s sense organ for smell:
    A. Olfactory epithelium B. Taste buds C. Tympanum D. Retina
    
    

69. Vision in frogs is via:
    A. Compound eyes B. Simple eyes with nictitating membrane C. Pineal eye D. None
    
    

70. Hearing in frogs is through:
    A. External ear B. Tympanum + internal ear C. Ossicles D. Nose
    
    

71. Equilibrium is maintained by:
    A. Tympanum B. Internal ear C. Eyes D. Nostrils
    
    

72. Male frog reproductive ducts:
    A. Vasa efferentia → kidney → Bidder’s canal → cloaca B. Oviducts C. Cloacal sac only D. None
    
    

73. Female frog reproductive tract:
    A. Ovaries + Oviduct → cloaca B. Testes only C. Cloacal sac only D. None
    
    

74. Fertilisation in frogs is:
    A. Internal B. External C. Both D. None
    
    

75. Development in frogs is:
    A. Direct B. Indirect via tadpole C. Binary fission D. Budding
    
    

76. Frog eggs are fertilised in:
    A. Water B. Cloaca C. Oviduct D. Stomach
    
    

77. Tadpole larva breathes with:
    A. Skin B. Gills C. Lungs D. Spiracles
    
    

78. Metamorphosis in frogs is regulated by:
    A. Insulin B. Thyroxine C. Estrogen D. Testosterone
    
    

79. Number of eggs per laying:
    A. 500 B. 1000 C. 2500–3000 D. 10,000
    
    

80. Role of frogs in ecosystem:
    A. Pest control B. Link in food chain C. Food for others D. All of these
    
    

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Miscellaneous & PYQs (Q81–Q100)

81. In mammals, RBCs are enucleated. In frogs they are:
    A. Enucleated B. Nucleated C. None D. Empty
    
    

82. Which system opens into cloaca?
    A. Digestive B. Reproductive C. Excretory D. All
    
    

83. Poikilothermic animals are:
    A. Birds B. Amphibians C. Mammals D. None
    
    

84. Copulatory pads in frogs are found on:
    A. Hindlimbs B. Forelimbs (first digit) C. Head D. Cloaca
    
    

85. Frog heart differs from mammalian heart by:
    A. Fewer chambers (3 vs 4) B. RBC nucleation C. Sinus venosus D. All
    
    

86. Portal systems ensure:
    A. Double circulation B. Blood detoxification C. Blood pooling D. None
    
    

87. Conus arteriosus ensures:
    A. Mixing of blood B. Direct oxygen supply C. Proper distribution of blood D. None
    
    

88. Frog respiration during swimming:
    A. Pulmonary B. Cutaneous C. Buccal D. Gills
    
    

89. Tympanum leads to:
    A. Mouth B. Buccal cavity C. Internal ear D. Cloaca
    
    

90. RBC in frog vs human:
    A. Frog – nucleated, Human – enucleated B. Both nucleated C. Both enucleated D. None
    
    

91. Kidneys in frogs are:
    A. Mesonephric B. Metanephric C. Pronephric D. None
    
    

92. Mesorchium attaches:
    A. Ovaries B. Testes C. Kidneys D. Cloaca
    
    

93. Ovum in frog passes through:
    A. Mesonephric duct B. Oviduct C. Cloaca D. Both B & C
    
    

94. Copulation in frog is called:
    A. Fertilisation B. Amplexus C. Cloacal kiss D. Gametogenesis
    
    

95. Metamorphosis involves:
    A. Tail resorption B. Limb development C. Lung development D. All
    
    

96. Hormone essential for frog metamorphosis:
    A. Thyroxine B. Insulin C. Glucagon D. Estrogen
    
    

97. Frogs are economically useful because:
    A. Eat pests B. Maintain food chain C. Indicator species D. All
    
    

98. Frogs are harmful when:
    A. They eat crops B. Carry pathogens C. Poisonous skin (in some species) D. Both B & C
    
    

99. Which structure absent in frog:
    A. Tail in adult B. Cloaca C. Eyes D. Kidney
    
    

100. Fertilisation site in frog:
     A. Cloaca B. Water outside body C. Oviduct D. Ovary
     
     

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✅ Answer Key

Q1–Q20: 1-A, 2-B, 3-C, 4-A, 5-B, 6-D, 7-A, 8-C, 9-A, 10-A, 11-B, 12-B, 13-A, 14-B, 15-C, 16-A, 17-C, 18-B, 19-B, 20-A
Q21–Q40: 21-B, 22-B, 23-B, 24-B, 25-C, 26-B, 27-B, 28-B, 29-D, 30-B, 31-B, 32-B, 33-B, 34-A, 35-B, 36-C, 37-B, 38-C, 39-C, 40-B
Q41–Q80: 41-B, 42-B, 43-C, 44-B, 45-C, 46-B, 47-B, 48-A, 49-B, 50-A, 51-B, 52-B, 53-A, 54-C, 55-B, 56-C, 57-C, 58-C, 59-B, 60-B, 61-A, 62-B, 63-B, 64-A, 65-B, 66-A, 67-B, 68-A, 69-B, 70-B, 71-B, 72-A, 73-A, 74-B, 75-B, 76-A, 77-B, 78-B, 79-C, 80-D
Q81–Q100: 81-B, 82-D, 83-B, 84-B, 85-D, 86-B, 87-C, 88-B, 89-C, 90-A, 91-A, 92-B, 93-D, 94-B, 95-D, 96-A, 97-D, 98-D, 99-A, 100-B

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