Structural Organisation in Animals - Frog Focus (NCERT Practice Paper)

Q1. Correct statements about the frog's hind limbs:
(i) Larger than fore limbs.
(ii) More muscular.
(iii) End in five digits.
(iv) Help in leaping and burrowing.

Correct Answer: (a)
All four statements are correct: hind limbs are larger, more muscular, have five digits, and are used for leaping and burrowing. They are the primary locomotory organs in frogs.

Q2. Which of the following are correct about the frog brain sub-divisions?
(i) Forebrain includes olfactory lobes.
(ii) Hind-brain includes cerebellum.
(iii) Hind-brain includes medulla oblongata.
(iv) Medulla passes out through foramen magnum.

Correct Answer: (a)
All four statements are correct: the forebrain includes olfactory lobes, the hindbrain includes cerebellum and medulla oblongata, and the medulla passes through the foramen magnum to the spinal cord.

Q3. Match the numbers and terms for frogs:

Column-I	Column-II
A. Heart chambers	(I) 10 pairs
B. Cranial nerves	(II) 3
C. Vasa efferentia	(III) 10-12

Correct Answer: (a)
The frog's heart has 3 chambers (II). There are 10 pairs of cranial nerves (I). Vasa efferentia number 10–12 (III). These are quantitative facts about frog anatomy, and the matching correctly pairs each term with its correct number.

Q4. Which statements about frog development are correct?
(i) Fertilisation is external.
(ii) Development is indirect (has a larval stage).
(iii) Tadpole is the larva.
(iv) Metamorphosis occurs.

Correct Answer: (a)
All four statements are correct: fertilisation is external, development is indirect with a tadpole larva, and metamorphosis transforms the tadpole into an adult. This describes the frog's life cycle.

Q5. Regarding sexual dimorphism in frogs:
(i) Males have vocal sacs.
(ii) Males have copulatory pads.
(iii) Copulatory pad is on the first digit of the forelimb.
(iv) Females have vocal sacs.

Correct Answer: (a)
Statements (i), (ii), and (iii) are correct: males have vocal sacs and copulatory pads on the first digit of the forelimb. Statement (iv) is false because females lack vocal sacs; they are male-specific.

Q6. Match the portal systems in frogs:

Column-I	Column-II
A. Hepatic portal	(I) Kidney and lower body
B. Renal portal	(II) Liver and intestine

Correct Answer: (a)
The hepatic portal system connects the intestine to the liver (II), allowing the liver to process absorbed nutrients. The renal portal system connects the kidney to the lower body parts (I), allowing blood from the hind limbs and tail to be filtered by the kidney before returning to the heart. This matching correctly identifies the two portal systems.

Q7. Which statement is correct regarding frog skin?
(i) It is smooth and slippery.
(ii) It is always maintained in a moist condition.
(iii) It absorbs water.
(iv) It contains mucous glands.

Correct Answer: (c)
Frog skin is smooth and slippery due to mucous glands, it is kept moist for cutaneous respiration, it absorbs water, and it contains mucous glands. All statements are accurate and describe the multifunctional nature of frog skin.

Q8. Assertion: The forebrain includes paired cerebral hemispheres. Reason: Midbrain is characterized by a pair of optic lobes.

Correct Answer: (b)
Both statements are anatomically correct: the forebrain consists of the cerebral hemispheres (among other parts), and the midbrain features a pair of optic lobes. However, the reason describes a different brain region (midbrain) and does not explain why the forebrain includes cerebral hemispheres. They are independent facts about different parts of the brain.

Q9. A frog never drinks water but absorbs it through the:

Correct Answer: (b)
Frogs absorb water directly through their highly permeable skin, which is rich in blood capillaries. This cutaneous absorption is the primary mode of water intake; they do not drink with their mouth. The skin must remain moist for efficient absorption, which is why frogs are often found near water bodies. This feature is linked to their amphibious lifestyle.

Q10. Male frogs can be distinguished from females by the presence of:

Correct Answer: (b)
Male frogs possess vocal sacs, which are distensible pouches that amplify their croaking calls during the breeding season, and copulatory pads on the first digit of the forelimbs to grip females during amplexus. These are secondary sexual characteristics absent in females. Webbed feet are present in both sexes, and eyes and nictitating membranes are similar.

Q11. The body of a frog is divisible into:

Correct Answer: (b)
A frog's body is clearly divided into two main parts: the head and the trunk. There is no distinct neck or tail in adult frogs, which is a characteristic feature of the class Amphibia. The absence of a neck facilitates a more streamlined body shape for swimming and jumping. This division is important for understanding its external anatomy.

Q12. Assertion: Final digestion in frogs takes place in the stomach. Reason: Gastric juices contain digestive enzymes.

Correct Answer: (d)
The assertion is false because final digestion occurs in the intestine, not the stomach. The stomach is the site of initial protein digestion, where gastric juices containing pepsin and HCl break down proteins into peptones. However, the complete breakdown of carbohydrates, proteins, and fats to absorbable units takes place in the small intestine (duodenum and ileum). The reason is true (gastric juices do contain enzymes), but it does not support the false assertion.

Q13. Assertion: The frog's brain is enclosed in a cranium. Reason: Cranium is a bony structure known as the brain box.

Correct Answer: (a)
The cranium is a bony case that surrounds and protects the brain, and it is commonly referred to as the brain box. Since the cranium is a rigid bony structure, it effectively encloses and safeguards the brain from mechanical injury. Therefore, the reason correctly explains why the brain is enclosed in a cranium.

Q14. Assertion: External ear is absent in frogs. Reason: Only tympanum can be seen externally.

Correct Answer: (a)
Frogs do not have an external ear (pinna); the ear is represented externally by a membranous tympanum located on the side of the head. The tympanum is the visible eardrum that receives sound vibrations. Since no outer ear structure exists, the tympanum serves as the external indicator of the ear. Thus the reason correctly explains the assertion.

Q15. Match the male reproductive parts:

Column-I	Column-II
A. Testes	(I) Adhered to kidney
B. Vasa efferentia	(II) 10-12 in number
C. Bidder’s canal	(III) Inside kidney

Correct Answer: (a)
Testes are attached to the upper part of the kidneys by mesorchium (I). Vasa efferentia are 10–12 fine ducts (II) that carry sperm from testes to kidneys. Bidder's canal is located inside the kidney (III), where vasa efferentia open. This matching correctly describes the anatomical arrangement of the male reproductive system in frogs.

Q16. Assertion: All complex animals consist of only four basic types of tissues. Reason: These tissues are organised in specific proportion and pattern to form an organ.

Correct Answer: (b)
The assertion is correct because all complex animals indeed have four primary tissue types: epithelial, connective, muscular and nervous. The reason is also correct as tissues combine in specific ways to form organs. However, the reason does not explain why there are exactly four tissue types; rather, it describes what happens after tissues are formed. The number of tissue types is a fundamental characteristic, not a consequence of organ formation. Hence the reason is not the correct explanation for the assertion.

Q17. The common species of frog found in India is:

Correct Answer: (b)
Rana tigrina is the most widely distributed species of frog in the Indian subcontinent. It is commonly found in freshwater ponds, lakes, and agricultural fields. The other species, such as Bufo melanostictus (toad), are less common or belong to different habitats. Correct identification of the species is crucial for studying its anatomy and life cycle in the Indian context.

Q18. Assertion: Skin acts as a respiratory organ in frogs on land. Reason: Frogs exhibit cutaneous respiration in water only.

Correct Answer: (c)
Skin is indeed a respiratory organ for frogs both on land and in water; it is used for gas exchange in all environments. The reason claims cutaneous respiration occurs only in water, which is incorrect. On land, frogs also use their skin, though less extensively than in water, supplementing pulmonary and buccal respiration. Thus the assertion is true, but the reason is false.

Q19. Select the correct statement about the heart's sinus venosus:
(i) It is triangular.
(ii) It joins the right atrium.
(iii) It receives oxygenated blood.
(iv) It receives blood via vena cava.

Correct Answer: (a)
Statements (i), (ii), and (iv) are correct: sinus venosus is triangular, joins the right atrium, and receives blood via vena cava. Statement (iii) is false because it receives deoxygenated blood, not oxygenated.

Q20. Match the respiratory organs with the environment:

Column-I	Column-II
A. Water	(I) Lungs, Buccal cavity, Skin
B. Land	(II) Skin only

Correct Answer: (a)
In water, frogs rely solely on cutaneous respiration (skin only) because lungs are inefficient in water. On land, they use a combination of lungs, buccal cavity (mouth lining), and skin for gas exchange. This matches correctly: A (water) → II (skin only), B (land) → I (lungs, buccal, skin).

Q21. Assertion: Male frogs have vocal sacs. Reason: Vocal sacs help in sound production during the breeding season.

Correct Answer: (a)
Male frogs possess vocal sacs, which are outpouchings of the mouth floor that amplify their croaking calls. These sacs are used during the breeding season to attract females and establish territory. The reason correctly explains the function of these structures, as they are specifically adapted for sound production. Thus both are true and the reason correctly explains the assertion.

Q22. Which statements about male reproductive system are true?
(i) Testes are yellowish ovoid bodies.
(ii) Vasa efferentia are 10-12 in number.
(iii) Sperms enter Bidder's canal.
(iv) Ureters act as urinogenital ducts.

Correct Answer: (a)
All four statements are true: testes are yellowish ovoid, vasa efferentia are 10–12, sperms enter Bidder's canal, and ureters serve as urinogenital ducts. This matches the detailed anatomy of the male reproductive system.

Q23. Assertion: Frog's blood is different from lymph. Reason: Lymph lacks RBCs and few proteins.

Correct Answer: (a)
Blood and lymph are distinct fluids; blood contains red blood cells, white blood cells, platelets, and plasma proteins, while lymph is a colourless fluid derived from interstitial fluid and lacks RBCs. Lymph also has fewer proteins than blood plasma. These differences make lymph a separate fluid with a different composition and function. Therefore the reason correctly explains why frog's blood is different from lymph.

Q24. Assertion: In male frogs, ureters act as urinogenital ducts. Reason: Ureters carry both urine and sperms to the cloaca.

Correct Answer: (a)
In male frogs, the ureters have a dual function: they transport urine from the kidneys to the cloaca and also carry sperms from the testes (via Bidder's canal) to the cloaca. Because they serve both urinary and reproductive roles, they are called urinogenital ducts. The reason correctly describes this dual function, thus explaining why they are designated as urinogenital ducts.

Q25. Match the blood components:

Column-I	Column-II
A. RBCs	(I) Leucocytes
B. WBCs	(II) Erythrocytes
C. Platelets	(III) Blood clotting

Correct Answer: (a)
RBCs are called erythrocytes (II), WBCs are leucocytes (I), and platelets are responsible for blood clotting (III). This matching uses standard haematological terminology correctly.

Q26. A triangular structure that joins the right atrium of the frog's heart is:

Correct Answer: (b)
The sinus venosus is a thin-walled, triangular chamber that receives deoxygenated blood from the major veins (venae cavae) and delivers it to the right atrium. The conus arteriosus is a vessel that leaves the ventricle and gives rise to aortic arches. The pericardium is the protective sac around the heart, and vena cava are veins. The sinus venosus is an important component of the frog's circulatory system.

Q27. Frogs are poikilotherms, which means they are:

Correct Answer: (b)
Poikilotherms, also known as cold-blooded animals, have body temperatures that fluctuate with the ambient environment. Frogs cannot regulate their internal temperature internally and rely on external heat sources. This contrasts with homeotherms (warm-blooded) like birds and mammals, which maintain a constant body temperature. This metabolic characteristic affects their behaviour, such as hibernation and aestivation.

Q28. Statements about frog's ecological role:
(i) They eat insects that damage crops.
(ii) They maintain ecological balance.
(iii) They are a link in the food web.
(iv) Their legs are used as food in some countries.

Correct Answer: (a)
All four statements are correct: frogs eat insects, help maintain balance, are part of the food web, and their legs are consumed in some cultures. These are all mentioned in the ecological context of the frog.

Q29. The organ in frogs that receives sound signals is the:

Correct Answer: (c)
The tympanum is a circular, membranous structure located on the side of the head that functions as the eardrum, receiving sound vibrations from the environment. Frogs lack an external ear (pinna), so the tympanum is the first point of sound reception. The internal ear then processes these signals. This is a key feature of amphibian hearing.

Q30. Regarding the heart of a frog:
(i) It has two atria and one ventricle.
(ii) It is covered by pericardium.
(iii) Sinus venosus receives blood from vena cava.
(iv) Conus arteriosus is on the dorsal side.

Correct Answer: (a)
Statements (i), (ii), and (iii) are correct: the heart has two atria and one ventricle, is covered by pericardium, and sinus venosus receives blood from vena cava. Statement (iv) is false because the conus arteriosus is on the ventral side, not dorsal.

Q31. The heart of a frog has how many chambers?

Correct Answer: (b)
The frog's heart consists of three chambers: two atria (left and right) and one ventricle. This is a characteristic feature of amphibians. The right atrium receives deoxygenated blood, while the left atrium receives oxygenated blood, but they mix in the single ventricle. This is less efficient than the four-chambered heart of birds and mammals but suits their metabolic needs.

Q32. Assertion: Frogs have nucleated RBCs. Reason: Hemoglobin is absent in frog's blood.

Correct Answer: (c)
Frog red blood cells are nucleated, which is a correct assertion. However, hemoglobin is present in frog's blood; it is the red pigment that gives blood its colour and carries oxygen. The absence of hemoglobin would make the blood colourless and unable to transport oxygen effectively. Therefore the reason is false, while the assertion is true.

Q33. How many pairs of cranial nerves arise from the brain of a frog?

Correct Answer: (b)
Frogs possess ten pairs of cranial nerves, which emerge from the brain and innervate structures of the head and neck. This number is intermediate between fishes (usually 10) and mammals (12). Each cranial nerve has specific functions related to sensory, motor, or mixed activities. This is a standard anatomical feature used in comparative vertebrate studies.

Q34. Match the brain parts with their sub-divisions:

Column-I	Column-II
A. Forebrain	(I) Diencephalon
B. Midbrain	(II) Optic lobes
C. Hindbrain	(III) Medulla oblongata

Correct Answer: (a)
The forebrain includes the diencephalon (I). The midbrain features optic lobes (II). The hindbrain includes the medulla oblongata (III). This is the correct anatomical subdivision of the frog's brain, with each region having specific components.

Q35. Match the digestive parts with their functions:

Column-I	Column-II
A. Tongue	(I) Emulsifies fat
B. Gastric juice	(II) Captures food
C. Bile	(III) Digestion in stomach
D. Villi	(IV) Absorption

Correct Answer: (a)
The tongue is used to capture prey (II). Gastric juice contains HCl and pepsin for digestion in the stomach (III). Bile, produced by the liver, emulsifies fats (I). Villi are finger-like projections in the intestine that increase surface area for absorption (IV). This matching correctly correlates each structure with its primary digestive function.

Q36. Assertion: The skin of the frog is smooth and slippery. Reason: Mucous glands are present in the skin.

Correct Answer: (a)
Frog skin contains numerous mucous glands that secrete a slimy substance, which keeps the skin moist and smooth. This mucus reduces friction and helps in cutaneous respiration and water absorption. The smooth, slippery texture is a direct result of the presence of these glands. Therefore the reason is the correct explanation for the assertion.

Q37. Assertion: In unicellular organisms, all functions are performed by a single cell. Reason: Multicellular animals exhibit division of labour.

Correct Answer: (b)
Both statements are true: unicellular organisms carry out all life processes within one cell, and multicellular animals have specialised cells, tissues and organs that divide labour. However, the reason does not explain the assertion because they are separate facts about different levels of organisation. The assertion is about unicellular organisms, while the reason is about multicellularity, so there is no causal relationship. Therefore the reason is not the correct explanation.

Q38. Match the terms with their definitions:

Column-I	Column-II
A. Morphology	(I) Study of internal organs
B. Anatomy	(II) Study of external features
C. Camouflage	(III) Protective coloration
D. Mimicry	(IV) Ability to change colour to hide

Correct Answer: (a)
Morphology is the study of external form and features, so it matches with II. Anatomy deals with internal organs, so it matches with I. Camouflage is the ability to change colour to blend with the environment for hiding (IV). Mimicry is protective coloration (III), where an organism resembles another object or species for defence. These definitions are standard in biology.

Q39. Select the correct statements about the frog's nervous system:
(i) It has 10 pairs of cranial nerves.
(ii) Brain is divided into fore-brain, mid-brain and hind-brain.
(iii) Midbrain has a pair of optic lobes.
(iv) Medulla oblongata continues into the spinal cord.

Correct Answer: (a)
All four statements are correct: there are 10 pairs of cranial nerves, the brain is divided into three regions, the midbrain contains optic lobes, and the medulla oblongata continues as the spinal cord. These are standard features of the frog's nervous system.

Q40. The study of the morphology of internal organs in animals is conventionally called:

Correct Answer: (b)
Anatomy is the branch of biology that deals with the internal structure of organisms, including the study of organs and organ systems. Morphology, on the other hand, covers both external form and internal structure, but in practice, anatomy specifically refers to internal organisation. Histology is the study of tissues, and physiology deals with functions. This terminology is standard in biological sciences.

Q41. Which statements about female reproductive system are true?
(i) Ovaries are situated near kidneys.
(ii) There is a functional connection between ovaries and kidneys.
(iii) A female lays 2500-3000 eggs at a time.
(iv) Fertilisation is external.

Correct Answer: (a)
Statements (i), (iii), and (iv) are correct: ovaries are near kidneys, females lay 2500–3000 eggs, and fertilisation is external. Statement (ii) is false because there is no functional connection between ovaries and kidneys; the ovaries are separate organs.

Q42. Choose the correct statements about frog blood cells:
(i) RBCs are nucleated.
(ii) RBCs contain hemoglobin.
(iii) WBCs are called leucocytes.
(iv) Platelets are present.

Correct Answer: (a)
All four statements are correct: RBCs are nucleated and contain hemoglobin, WBCs are leucocytes, and platelets are present in frog blood. These are standard features of frog hematology.

Q43. Which statements about the frog's vascular system are correct?
(i) It is a closed type.
(ii) Heart has 3 chambers.
(iii) RBCs are nucleated.
(iv) Lymph lacks RBCs.

Correct Answer: (a)
All four statements are correct: the vascular system is closed, the heart has three chambers, RBCs are nucleated, and lymph does not contain RBCs. These are key features of the frog's circulatory system.

Q44. Regarding frog sense organs, which are correct?
(i) Eyes are simple eyes.
(ii) External ear is absent.
(iii) Sensory papillae are organs of taste.
(iv) Tympanum is an organ of hearing.

Correct Answer: (a)
Statements (i), (ii), and (iv) are correct: eyes are simple (non-compound) eyes, external ear is absent, and the tympanum is for hearing. Statement (iii) is wrong because sensory papillae are for touch; taste buds are for taste.

Q45. Match the circulatory structures:

Column-I	Column-II
A. Arteries	(I) Carry blood from heart
B. Veins	(II) Collect blood to heart

Correct Answer: (a)
Arteries carry blood away from the heart (I), and veins return blood to the heart (II). This is the fundamental definition of these blood vessels in the circulatory system.

Q46. In frogs, the liver secretes bile which is stored in the:

Correct Answer: (b)
The liver produces bile, a digestive fluid that helps emulsify fats, and this bile is temporarily stored in the gall bladder. When needed, bile is released into the duodenum through the bile duct. The pancreas secretes pancreatic juice, not bile. The stomach and duodenum are parts of the alimentary canal where digestion occurs, but they do not store bile.

Q47. Assertion: Frogs take shelter in deep burrows during peak summer and winter. Reason: Frogs are poikilotherms and cannot maintain a constant body temperature.

Correct Answer: (a)
Frogs are cold-blooded (poikilotherms), so their body temperature varies with the environment. During extreme heat or cold, they cannot tolerate the temperature fluctuations and therefore burrow into mud or hide in crevices to avoid lethal conditions. This behaviour (aestivation in summer and hibernation in winter) is directly caused by their inability to regulate body temperature internally. Thus the reason correctly explains the assertion.

Q48. Assertion: Epithelia have one free surface. Reason: Epithelia line the body's surface and its cavities.

Correct Answer: (b)
Epithelial tissue does have a free surface exposed to the exterior or to a body cavity, and it is also true that epithelia line surfaces and cavities. However, the lining function does not explain why they have a free surface; the free surface is a fundamental structural feature of epithelia, while lining is a functional role. The reason is true but is not the correct explanation for the presence of a free surface.

Q49. The excretory system of a frog includes a pair of kidneys which are:

Correct Answer: (a)
The kidneys of a frog are compact, bean-shaped organs that are dark red in colour due to their rich blood supply. They are situated in the posterior body cavity, attached to the dorsal body wall. These are mesonephric kidneys typical of adult amphibians. Their shape and colour help in their identification during dissection.

Q50. Match the organs with their systems in frogs:

Column-I (Organ)	Column-II (System)
A. Kidneys	(I) Digestive
B. Pancreas	(II) Excretory
C. Sinus venosus	(III) Nervous
D. Medulla oblongata	(IV) Vascular

Correct Answer: (a)
Kidneys are part of the excretory system (II), filtering waste from blood. Pancreas is a digestive gland (I) secreting enzymes and hormones. Sinus venosus is a vascular structure (IV), specifically part of the heart. Medulla oblongata belongs to the nervous system (III), as it is a part of the brain. This matching correctly assigns each organ to its system.

Q51. Match the endocrine glands with frog biology:

Column-I	Column-II
A. Thyroid	(I) Endocrine gland
B. Pancreatic islets	(II) Endocrine gland
C. Adrenals	(III) Endocrine gland

Correct Answer: (a)
All three—thyroid, pancreatic islets (islets of Langerhans), and adrenal glands—are endocrine glands that secrete hormones directly into the blood. Since each is an endocrine gland, any matching of A-I, B-II, C-III is correct as a distinct pairing; option 0 is chosen as the standard answer.

Q52. Match the excretory structures in frogs:

Column-I	Column-II
A. Uriniferous tubules	(I) Common exit for waste and gametes
B. Ureter (Male)	(II) Nephrons
C. Cloaca	(III) Urinogenital duct

Correct Answer: (a)
Uriniferous tubules are the nephrons (II), the functional units of the kidney. In male frogs, the ureter serves as the urinogenital duct (III), carrying both urine and sperm. The cloaca is the common chamber (I) where digestive, excretory, and reproductive tracts open. This matching accurately describes the excretory anatomy.

Q53. Assertion: A frog's neck is absent. Reason: It helps the frog to leap more effectively.

Correct Answer: (c)
It is true that frogs lack a neck; the head is directly attached to the trunk. However, the reason given—that this helps leaping—is not supported by anatomical evidence. The absence of a neck is a primitive feature inherited from early vertebrates and is not specifically an adaptation for jumping. Frogs leap using powerful hind limbs, not because of the lack of a neck. Therefore the assertion is true, but the reason is false.

Q54. Correct statements about epithelial tissue (from summary):
(i) Sheet like tissues.
(ii) Line body surface and cavities.
(iii) One free surface facing fluid or environment.
(iv) Cells are connected at junctions.

Correct Answer: (a)
All four statements are correct: epithelia are sheet-like, line surfaces and cavities, have a free surface, and cells are connected by junctions. These are defining characteristics of epithelial tissue.

Q55. Identify the correct statements regarding frog locomotion:
(i) Hind limbs end in 5 digits.
(ii) Fore limbs end in 4 digits.
(iii) Hind limbs are larger and more muscular than fore limbs.
(iv) Feet have webbed digits for swimming.

Correct Answer: (a)
All four statements are correct: hind limbs have 5 digits, fore limbs have 4, hind limbs are larger and more muscular, and feet are webbed for swimming. These features are adapted for jumping and swimming.

Q56. Assertion: Frogs are beneficial for mankind. Reason: They eat insects and protect crops.

Correct Answer: (a)
Frogs are insectivorous and consume large numbers of insects, many of which are agricultural pests. By reducing pest populations, they help protect crops and reduce the need for chemical pesticides. This direct benefit to agriculture is why they are considered beneficial to humans. Thus the reason correctly explains the assertion.

Q57. Assertion: Frogs maintain ecological balance. Reason: They serve as an important link in the food chain.

Correct Answer: (a)
Frogs occupy a crucial position in the food web: they consume insects (primary consumers) and are preyed upon by snakes, birds, and other animals. By regulating insect populations and providing food for higher trophic levels, they help maintain ecological balance. This role as a link in the food chain directly explains their contribution to ecological stability.

Q58. Summer sleep in frogs is known as:

Correct Answer: (b)
Aestivation is a period of dormancy during hot and dry summer conditions, allowing frogs to conserve water and energy. It is different from hibernation, which is winter sleep. During aestivation, frogs burrow into mud or find cool, moist places to avoid desiccation. This adaptation is crucial for survival in tropical regions with seasonal droughts.

Q59. Match digits count again:

Column-I	Column-II
A. Fore limb	(I) 4
B. Hind limb	(II) 5

Correct Answer: (a)
Fore limbs have 4 digits (I), hind limbs have 5 digits (II). This is the same as in Q65, confirming the anatomical digit count.

Q60. Assertion: Frogs do not drink water. Reason: They absorb water through their skin.

Correct Answer: (a)
Frogs lack a drinking behaviour; instead, they absorb water directly through their highly permeable skin. This cutaneous absorption is the primary means of water uptake, and the skin must remain moist for this process. The reason correctly explains why they do not need to drink: their skin fulfills the water requirement, so the mouth is not used for drinking.

Q61. Regarding the frog's portal system:
(i) Hepatic portal system connects liver and intestine.
(ii) Renal portal system connects kidney and lower body parts.
(iii) These are venous connections.
(iv) Arteries are part of the portal system.

Correct Answer: (a)
Statements (i), (ii), and (iii) are correct: the hepatic portal system connects liver and intestine, the renal portal system connects kidney and lower body, and both are venous connections. Statement (iv) is wrong because portal systems are venous, not arterial.

Q62. Match the following for frog skin:

Column-I	Column-II
A. Dorsal side	(I) Pale yellow
B. Ventral side	(II) Olive green with spots

Correct Answer: (a)
The dorsal (upper) surface of a frog is typically olive green with dark spots (II) for camouflage. The ventral (lower) surface is pale yellow (I), which helps in blending with the lighter background when viewed from below. This colouration is a common adaptive feature.

Q63. Assertion: Sinus venosus is a triangular structure. Reason: It receives blood from the arteries.

Correct Answer: (c)
The sinus venosus is indeed a triangular chamber in the frog's heart. However, it receives deoxygenated blood from the major veins (venae cavae), not from arteries. Arteries carry blood away from the heart, while veins return blood to the heart. Therefore the reason is false, even though the assertion is true.

Q64. Match the frog's sleep patterns:

Column-I	Column-II
A. Summer sleep	(I) Hibernation
B. Winter sleep	(II) Aestivation

Correct Answer: (a)
Summer sleep is called aestivation (II), a dormancy during hot, dry periods to avoid dehydration and heat. Winter sleep is hibernation (I), a dormancy during cold months to conserve energy when food is scarce. These terms are specific to the season and the animal's response to extreme environmental conditions.

Q65. Assertion: Fertilisation in frogs is external. Reason: It takes place in water.

Correct Answer: (a)
In frogs, the male releases sperms and the female releases eggs into the water simultaneously, where fertilisation occurs outside the body. This is the definition of external fertilisation. Because the gametes are shed into an aquatic environment, the process must take place in water. Therefore the reason correctly explains why fertilisation is external.

Q66. Match the following frog features:

Column-I	Column-II
A. Vocal sacs	(I) Only in males
B. Oviducts	(II) Open separately in cloaca
C. Eggs	(III) 2500-3000 at a time

Correct Answer: (a)
Vocal sacs are present only in male frogs (I). Oviducts are paired female ducts that open separately into the cloaca (II). Female frogs lay 2500–3000 eggs at a time (III). This matching correctly captures sexual dimorphism and reproductive output.

Q67. Match heart coverings:

Column-I	Column-II
A. Heart	(I) Pericardium
B. Lungs	(II) Sac-like structure

Correct Answer: (a)
The heart is enclosed in a pericardium (I), and lungs are sac-like structures (II) for gas exchange. This matching correctly identifies the protective and structural coverings of these organs.

Q68. Correct statements about frog sense organs:
(i) External ear is absent.
(ii) Nasal epithelium is for smell.
(iii) Taste buds are for taste.
(iv) Tympanum is for hearing.

Correct Answer: (a)
All four statements are correct: external ear is absent, nasal epithelium is for smell, taste buds are for taste, and tympanum is for hearing. This covers the major sense organs in frogs.

Q69. Regarding the digestive system of a frog:
(i) Alimentary canal is short.
(ii) Food is captured by a bilobed tongue.
(iii) Digestion of food takes place by HCl and gastric juices.
(iv) Liver secretes pancreatic juice.

Correct Answer: (a)
Statements (i), (ii), and (iii) are correct: the alimentary canal is short, the tongue is bilobed and used to capture prey, and digestion in the stomach involves HCl and gastric juices. Statement (iv) is wrong because the liver secretes bile, not pancreatic juice; pancreatic juice is secreted by the pancreas.

Q70. Which are correct about frog brain box?
(i) Bony structure.
(ii) Called cranium.
(iii) Encloses the brain.
(iv) Cranial nerves pass through it.

Correct Answer: (a)
All four statements are correct: the cranium is bony, also called the brain box, it encloses the brain, and cranial nerves pass through foramina in it. These are true of the frog's skull.

Q71. Vasa efferentia in male frogs open into:

Correct Answer: (c)
The vasa efferentia, which number 10–12, are fine ducts that arise from the testes and enter the kidneys, where they join the Bidder's canal. The Bidder's canal is a longitudinal channel within the kidney that collects sperms and then leads them to the ureter. The ureter then transports both sperm and urine to the cloaca. This arrangement is unique to amphibians and is part of the urinogenital system.

Q72. Assertion: The length of the intestine is reduced in frogs. Reason: Frogs are carnivores.

Correct Answer: (a)
Frogs are carnivorous, feeding on insects and other small animals, which are relatively easy to digest. Carnivores typically have shorter intestines because meat requires less processing and absorption time than plant matter. The reduction in intestinal length is an adaptive feature linked to their diet, so the reason correctly explains why the intestine is short.

Q73. Assertion: Frogs have a hepatic portal system. Reason: It is a special venous connection between the liver and intestine.

Correct Answer: (a)
A hepatic portal system is a venous network that carries blood from the gastrointestinal tract and spleen to the liver before returning to the heart. This allows the liver to process nutrients and detoxify substances. The reason correctly defines this portal system as a venous connection between the intestine and liver. Thus the reason is the correct explanation for the assertion.

Q74. The RBCs of frogs are:

Correct Answer: (b)
Frog red blood cells (erythrocytes) are nucleated, meaning they contain a nucleus, and they contain hemoglobin, the oxygen-carrying pigment. In contrast, mammalian RBCs are non-nucleated. The presence of a nucleus is a characteristic of amphibian and avian red cells. Hemoglobin gives the blood its red colour and enables efficient oxygen transport.

Q75. Identify the correct statements about frog respiration:
(i) In water, skin acts as the respiratory organ.
(ii) On land, buccal cavity, skin and lungs act as respiratory organs.
(iii) Respiration by lungs is called pulmonary respiration.
(iv) During aestivation, gaseous exchange takes place through lungs.

Correct Answer: (a)
Statements (i), (ii), and (iii) are correct: in water, only skin is used; on land, the buccal cavity, skin, and lungs are used; and lung respiration is pulmonary. Statement (iv) is false because during aestivation and hibernation, gas exchange occurs through the skin, not lungs, as the frog is inactive and relies on cutaneous respiration.

Q76. The larval stage of a frog is called:

Correct Answer: (c)
The tadpole is the free-living, aquatic larval stage of a frog, which undergoes metamorphosis to become an adult. Tadpoles have gills, a tail, and a lateral line system, and they are herbivorous. Caterpillars are insect larvae, maggots are fly larvae, and nymphs are immature stages of insects with incomplete metamorphosis. The tadpole stage is characteristic of amphibians.

Q77. Which of the following is true for the urinary bladder of a frog?
(i) It is thin-walled.
(ii) It is situated ventral to the rectum.
(iii) It opens into the cloaca.
(iv) It stores urea before excretion.

Correct Answer: (a)
All four statements are true: the urinary bladder is thin-walled, lies ventral to the rectum, opens into the cloaca, and stores urine (which contains urea) before excretion. These are anatomical and functional details.

Q78. Match the brain regions of a frog:

Column-I	Column-II
A. Fore-brain	(I) Optic lobes
B. Mid-brain	(II) Cerebellum and Medulla
C. Hind-brain	(III) Olfactory lobes and Cerebrum

Correct Answer: (a)
The forebrain consists of olfactory lobes and cerebrum (III). The midbrain is dominated by a pair of optic lobes (I). The hindbrain includes the cerebellum and medulla oblongata (II). This is the standard subdivision of the frog's brain, and the matching correctly pairs each region with its components.

Q79. Which statements regarding the excretory system are correct?
(i) It consists of a pair of kidneys and ureters.
(ii) Urinary bladder is thin-walled.
(iii) Frog is an uricotelic animal.
(iv) Excretory wastes are carried by blood into the kidneys.

Correct Answer: (a)
Statements (i), (ii), and (iv) are correct: the excretory system includes kidneys and ureters, the urinary bladder is thin-walled, and wastes are carried by blood to the kidneys. Statement (iii) is wrong because frogs are ureotelic (excrete urea), not uricotelic.

Q80. Match the tissue definitions:

Column-I	Column-II
A. Epithelia	(I) Face body fluid or environment
B. Junctions	(II) Connect cells structurally

Correct Answer: (a)
Epithelial tissues have a free surface that faces either a body fluid or the external environment (I). Cellular junctions are structures that connect cells to one another (II). This matching correctly distinguishes epithelial characteristics from cell junctions.

Q81. In multicellular animals, a group of similar cells along with intercellular substances performing a specific function is called:

Correct Answer: (c)
A tissue is defined as a group of similar cells that work together to perform a particular function. In complex animals, cells are organised into tissues, which are the first level of structural organisation. Tissues then combine to form organs, and organs into organ systems. This definition is fundamental to understanding animal anatomy and is the basis for all higher-level organisation.

Q82. The ability of frogs to change colour to hide from enemies is called:

Correct Answer: (c)
Camouflage is the adaptive strategy where an animal blends with its surroundings to avoid predators or to ambush prey. Frogs can alter their skin pigmentation to match the background, providing protection. Aestivation and hibernation are physiological states for surviving extreme temperatures, while metamorphosis is a developmental process. Camouflage is an important survival mechanism in many amphibians.

Q83. Which statement is true for the frog's digestive process?
(i) Tongue is bilobed.
(ii) Stomach secretes HCl.
(iii) Chyme is partially digested food.
(iv) Duodenum is the first part of the small intestine.

Correct Answer: (a)
All four statements are correct: the tongue is bilobed, the stomach secretes HCl, chyme is partially digested food, and the duodenum is the first part of the small intestine. These are accurate physiological descriptions.

Q84. In male frogs, testes are adhered to the kidneys by a double fold of peritoneum called:

Correct Answer: (b)
The mesorchium is a double fold of peritoneum that suspends and attaches the testes to the dorsal body wall, specifically to the upper part of the kidneys. The pericardium encloses the heart, and the peritoneum is the general lining of the abdominal cavity. Oviducts are female reproductive ducts. This structure ensures the testes are held firmly in place.

Q85. Assertion: Kidneys are the primary excretory organs in frogs. Reason: Each kidney is composed of nephrons.

Correct Answer: (a)
The kidneys are the main excretory organs, responsible for filtering waste from the blood and producing urine. Each kidney is made up of numerous functional units called nephrons, which are responsible for filtration, reabsorption, and secretion. The presence of nephrons is the structural basis for the kidney's excretory function, so the reason correctly explains why kidneys are the primary excretory organs.

Q86. Assertion: Tadpoles undergo metamorphosis to become adults. Reason: Metamorphosis involves a series of developmental changes.

Correct Answer: (b)
Both statements are true: tadpoles do undergo metamorphosis, which is a series of changes that transform them into adult frogs. However, the reason merely defines metamorphosis as a series of developmental changes; it does not explain why tadpoles undergo this process. The fact that metamorphosis involves changes does not, by itself, explain the phenomenon; it is a definition, not a causal explanation.

Q87. Assertion: Frogs have a three-chambered heart. Reason: The heart of a frog is covered by a pericardium.

Correct Answer: (b)
The frog's heart has three chambers (two atria and one ventricle), which is a correct assertion. It is also true that the heart is enclosed in a pericardial sac. However, the pericardium does not explain why the heart has three chambers; its function is protective, not structural. The reason is true but does not provide the correct explanation for the number of chambers.

Q88. Match the phylum and class of frog:

Column-I	Column-II
A. Phylum	(I) Chordata
B. Class	(II) Amphibia

Correct Answer: (a)
Frogs belong to Phylum Chordata (I) and Class Amphibia (II). This is the correct taxonomic classification.

Q89. The alimentary canal in frogs is short because they are:

Correct Answer: (c)
Frogs are carnivorous, feeding on insects and other small animals. A short alimentary canal is typical of carnivores because meat is easier to digest and does not require the extensive fermentation and absorption needed for plant material. Herbivores, in contrast, have longer intestines for processing cellulose. This anatomical adaptation reflects their dietary habits.

Q90. Frog is a ureotelic animal because it excretes:

Correct Answer: (c)
Ureotelic animals, like frogs, excrete nitrogenous waste mainly as urea, which is less toxic than ammonia and requires less water for excretion. This is an adaptation for terrestrial life, as urea can be concentrated and excreted with minimal water loss. Ammonotelic animals excrete ammonia, and uricotelic animals excrete uric acid (common in birds and reptiles). This classification reflects evolutionary adaptations.

Q91. Digested food in frogs is absorbed by:

Correct Answer: (c)
The inner lining of the frog's intestine is folded into numerous finger-like projections called villi, and the epithelial cells have microvilli, which greatly increase the surface area for absorption of nutrients. The stomach is involved in digestion, the rectum stores undigested waste, and the cloaca is a common chamber for excretory and reproductive products. Absorption is efficient due to this specialised structure.

Q92. How many basic types of tissues are found in all complex animals?

Correct Answer: (c)
All complex animals possess exactly four basic types of tissues: epithelial, connective, muscular, and nervous. These tissues are present in various proportions and patterns to form different organs. Each tissue type has a distinct structure and function, contributing to the overall physiology of the organism. This classification is universally accepted in zoology and forms the foundation of histology.

Q93. Respiration through the skin in frogs is called:

Correct Answer: (b)
Cutaneous respiration refers to the exchange of gases through the skin, which is moist and highly vascularised. This is the primary mode of respiration in water and also occurs on land. Pulmonary respiration involves lungs, buccal respiration uses the lining of the mouth, and branchial respiration uses gills (which are absent in adult frogs). This dual respiratory capability is an amphibian trait.

Q94. Which of the following statements about frog morphology are correct?
(i) Head and trunk are present.
(ii) Neck and tail are absent.
(iii) A pair of nostrils is present above the mouth.
(iv) Tympanum represents the ear.

Correct Answer: (c)
All four statements are correct: frogs have a distinct head and trunk, no neck or tail, a pair of nostrils above the mouth, and a tympanum that serves as the ear. These are standard external features described in frog anatomy.

Q95. Match the sense organs with their type:

Column-I	Column-II
A. Sensory papillae	(I) Smell
B. Nasal epithelium	(II) Vision
C. Eyes	(III) Touch
D. Tympanum	(IV) Hearing

Correct Answer: (a)
Sensory papillae are involved in the sense of touch (III). Nasal epithelium contains olfactory receptors for smell (I). Eyes are the organs of vision (II). The tympanum functions as the hearing organ (IV). This matching correctly assigns each sense organ to its sensory modality.

Q96. Match the evolutionary trend terms:

Column-I	Column-II
A. Discernable trend	(I) Evolutionary trend
B. Tissues to Organ	(II) Increased complexity

Correct Answer: (a)
A discernable trend in evolution is indeed an evolutionary trend (I). The progression from tissues to organs represents an increase in organisational complexity (II). This matching correctly pairs the terms with their descriptions.

Q97. In frogs, the eyes are protected while in water by a:

Correct Answer: (b)
The nictitating membrane is a transparent, movable third eyelid that covers and protects the eye during swimming and when the frog is submerged. It keeps the eye moist and clear while allowing vision. The tympanum is the eardrum, vocal sacs are for sound production in males, and copulatory pads are used for grasping females during mating. This membrane is an adaptation for an aquatic and terrestrial life.

Q98. Match the limbs with their digit counts:

Column-I	Column-II
A. Fore limbs	(I) 5 digits
B. Hind limbs	(II) 4 digits

Correct Answer: (a)
Fore limbs of frogs have 4 digits (II), while hind limbs have 5 digits (I). This is a characteristic anatomical feature used for locomotion and grasping. The hind limbs are also webbed for swimming.

Q99. Match frog's larval stage feature:

Column-I	Column-II
A. Tadpole	(I) Metamorphosis
B. Adult	(II) Frog

Correct Answer: (a)
The tadpole is the larval stage that undergoes metamorphosis (I). The adult stage is the frog (II). This matching correctly describes the life cycle of a frog.

Q100. Match the excretory product types:

Column-I	Column-II
A. Ureotelic	(I) Urea
B. Ammonotelic	(II) Ammonia (not mentioned for frog but standard)

Correct Answer: (a)
Ureotelic animals excrete urea (I), while ammonotelic animals excrete ammonia (II). Frogs are ureotelic, so they excrete urea. This matching correctly classifies based on nitrogenous waste products.