401. Link each digestive structure with its principal relation. Each Column II entry is used once.
| Column I | Column II |
|---|
| P. Liver | W. Produces enzyme-containing pancreatic juice |
| Q. Gall bladder | X. Receives bile and pancreatic juice in the intestinal pathway |
| R. Pancreas | Y. Secretes bile |
| S. Duodenum | Z. Stores bile |
ⓐ. P-Z, Q-Y, R-X, S-W
ⓑ. P-W, Q-X, R-Z, S-Y
ⓒ. P-Y, Q-Z, R-W, S-X
ⓓ. P-X, Q-W, R-Y, S-Z
Correct Answer: P-Y, Q-Z, R-W, S-X
Explanation: The liver produces bile, so P matches Y. The gall bladder stores the bile supplied by the liver and releases it when required, giving Q with Z. The pancreas produces pancreatic juice containing digestive enzymes, so R matches W. In the frog digestive pathway, bile and pancreatic juice reach the duodenum through a common duct route, which links S with X. These structures cooperate but do not perform identical functions. Production, storage, enzymatic secretion, and reception occur in different organs or regions. The gall bladder does not manufacture bile, and the liver is not simply a storage sac. Correct mapping preserves the direction in which secretions move from their sources toward the intestinal site where they act on food.
402. Assess the following statements about the liver, gall bladder, and pancreas of a frog.
I. The liver secretes bile.
II. The gall bladder stores bile.
III. The pancreas produces pancreatic juice containing digestive enzymes.
IV. Bile is produced by the gall bladder and stored in the liver.
ⓐ. I is true; II is false; III is false; IV is true
ⓑ. I is true; II is true; III is true; IV is false
ⓒ. I is false; II is true; III is false; IV is true
ⓓ. I is true; II is true; III is true; IV is true
Correct Answer: I is true; II is true; III is true; IV is false
Explanation: The liver is the source of bile, making statement I valid. The gall bladder receives and stores this secretion until it is released into the digestive pathway, so statement II is also correct. The pancreas produces pancreatic juice containing enzymes that act on major food components, supporting statement III. Statement IV reverses production and storage. The gall bladder does not produce the bile that it contains, and the liver is not the organ in which that secretion is stored before release. The valid combination distinguishes two closely associated organs by function and also keeps pancreatic secretion separate from bile. This division of labour allows digestive products from different sources to reach the duodenum and contribute different actions.
403. The common duct carrying bile and pancreatic juice into the duodenum becomes completely blocked. Which outcome is most directly expected?
ⓐ. Food can no longer enter the mouth
ⓑ. Gastric hydrochloric acid can no longer be produced in the stomach
ⓒ. The rectum can no longer pass residue into the cloaca
ⓓ. Less bile and pancreatic juice reach the duodenum
Correct Answer: Less bile and pancreatic juice reach the duodenum
Explanation: In the frog digestive pathway, bile and pancreatic juice reach the duodenum through a common duct. A complete blockage reduces delivery of both secretions to the intestinal lumen. Bile-dependent emulsification of fats and enzyme-based digestion by pancreatic juice would be impaired. Ingestion through the mouth and acid secretion in the stomach occur upstream and do not depend on this duct remaining open. The rectum and cloaca lie farther posteriorly and can remain structurally connected even though digestion earlier in the canal is less effective. The condition demonstrates how one shared pathway can influence two secretions produced by different organs. The blockage occurs after bile and pancreatic juice have been produced, so it disrupts their delivery pathway without establishing that either gland has stopped secretion. The immediate defect is at their entry into the duodenum, not at their original sites of production.
404. The gall bladder of a frog is removed without damaging the liver or the duct leading toward the intestine. Which outcome is most likely at first?
ⓐ. Bile production continues, but storage before release is reduced
ⓑ. Bile production stops because the gall bladder synthesises bile
ⓒ. Pancreatic juice is converted into bile inside the liver
ⓓ. The intestine can no longer absorb any digested nutrient
Correct Answer: Bile production continues, but storage before release is reduced
Explanation: The liver produces bile, whereas the gall bladder mainly stores that secretion before it is released into the intestinal pathway. Removing the storage organ does not immediately remove the liver cells that synthesise bile, so production can continue. The pattern of storage and delivery may change, but the two functions must not be merged. Pancreatic juice is produced by the pancreas and remains a separate digestive secretion. Intestinal absorption also depends on villi, microvilli, and completed digestion, so loss of the gall bladder does not abolish every absorptive process. The changed condition tests division of labour between closely associated organs: one forms the secretion and the other holds it temporarily. Preserving the liver and duct is what allows bile production and passage to remain possible despite reduced storage. The organ-specific roles therefore remain distinguishable.
405. Two frogs receive identical fatty and protein-rich meals. In Group P, bile entry into the duodenum is blocked, but pancreatic juice enters normally. Group Q has no blockage. Which pattern is most consistent?
ⓐ. P loses every digestive process in the stomach and intestine
ⓑ. P shows normal fat emulsification but no pancreatic digestion
ⓒ. P has less fat emulsification but retains pancreatic digestion
ⓓ. P produces no food residue because bile is the only digestive secretion
Correct Answer: P has less fat emulsification but retains pancreatic digestion
Explanation: Bile assists digestion by emulsifying fats, which breaks large fat masses into smaller droplets and improves access for subsequent digestive action. Blocking bile entry reduces this emulsification step. Pancreatic juice is explicitly stated to enter normally, so its enzymes can still act on carbohydrates and proteins and contribute to other digestive reactions. The treatment does not remove gastric secretion or every intestinal process. It also does not prevent formation of undigested residue. The comparison isolates one secretion while preserving another, demonstrating that bile and pancreatic juice have complementary rather than identical roles. Pancreatic juice enters normally. This preserved condition isolates the consequence of the selective change. Only the function most directly dependent on the changed feature should be inferred from these conditions. Group P should show a selective weakness in fat handling alongside continued pancreatic enzyme activity.
406. The bilobed tongue of a frog is most directly adapted for:
ⓐ. grinding prey between hard chitinous teeth
ⓑ. capturing prey and drawing it into the mouth
ⓒ. storing bile before intestinal release
ⓓ. absorbing digested food through microvilli
Correct Answer: capturing prey and drawing it into the mouth
Explanation: The frog uses its bilobed tongue as a prey-capture structure. It can be projected rapidly toward small moving animals such as insects and then retract to bring the captured prey into the mouth. Grinding by hard chitinous teeth describes a different digestive design and is not the role of the frog tongue. Bile storage occurs in the gall bladder, while microvilli belong to the intestinal absorptive surface. The tongue acts at the ingestion stage before gastric and intestinal digestion begin. Its form and mobility are suited to securing prey rather than mechanically reducing it into fine particles. This feeding adaptation is consistent with the frog's carnivorous habit and its reliance on rapid capture of small animals.
407. Sequence the following events in the early digestive pathway of a frog.
P. Partially digested chyme enters the duodenum.
Q. The bilobed tongue captures prey.
R. Food passes through the oesophagus.
S. Hydrochloric acid and gastric juice act in the stomach.
ⓐ. \(R \rightarrow Q \rightarrow S \rightarrow P\)
ⓑ. \(Q \rightarrow S \rightarrow R \rightarrow P\)
ⓒ. \(Q \rightarrow R \rightarrow S \rightarrow P\)
ⓓ. \(S \rightarrow Q \rightarrow P \rightarrow R\)
Correct Answer: \(Q \rightarrow R \rightarrow S \rightarrow P\)
Explanation: The sequence begins when the bilobed tongue captures prey and brings it into the mouth. After passage through the buccal cavity and pharynx, food travels through the oesophagus, represented by R. It then enters the stomach, where hydrochloric acid and gastric juice initiate substantial chemical digestion, giving S. The resulting partially digested semi-fluid material is chyme, which passes into the duodenum, represented by P. Each stage depends on the previous one: gastric digestion cannot occur before food reaches the stomach, and chyme cannot enter the duodenum before it is formed. The first required event is that the bilobed tongue captures prey; the last is that partially digested chyme enters the duodenum; the intermediate steps preserve the direction of the pathway from cause to outcome. The correct order links prey capture, conduction, gastric processing, and transfer to the intestinal region.
408. Gastric glands of a frog stop releasing hydrochloric acid and other gastric juice, while the tongue, oesophagus, and intestine remain functional. The most direct effect is:
ⓐ. impaired gastric digestion and abnormal chyme formation
ⓑ. impaired tongue-based capture and swallowing of prey
ⓒ. impaired hepatic production and release of bile
ⓓ. impaired opening and emptying through the cloacal aperture
Correct Answer: impaired gastric digestion and abnormal chyme formation
Explanation: Acidic gastric secretions act within the stomach and help convert swallowed food into partially digested chyme. When those secretions are absent, food may still be captured, swallowed, and delivered through the oesophagus, but normal gastric digestion is weakened. Material entering the duodenum would be less effectively processed at the stomach stage. The liver can continue producing bile, and the cloacal aperture can remain open, since neither structure depends directly on gastric secretion. The changed condition isolates a chemical function while preserving food capture and canal continuity. The tongue, oesophagus, and intestine remain functional; preserving this condition confines the immediate inference to the selectively altered feature. The most immediate consequence concerns the quality of digestion and chyme formation within the stomach.
409. A semi-fluid sample collected where the stomach empties into the duodenum contains partially digested food mixed with gastric juice. The sample is:
ⓐ. bile stored before release
ⓑ. chyme
ⓒ. undigested residue ready for egestion
ⓓ. pancreatic juice
Correct Answer: chyme
Explanation: Chyme is the semi-fluid, partially digested material produced in the stomach when food mixes with hydrochloric acid and gastric juice. Its location at the stomach-duodenum boundary is consistent with the next stage of the digestive pathway, where bile, pancreatic juice, and intestinal processes continue digestion. Bile and pancreatic juice are secretions added to food; neither is the food-containing mixture itself. Undigested residue is formed later, after digestion and absorption have removed useful nutrients, and then passes toward the rectum and cloaca. The identification therefore depends on composition, digestive stage, and position. Calling any fluid in the duodenum chyme would be too broad, but the stated mixture of partially digested food and gastric secretion fits the term precisely. Its position at the stomach-duodenum junction links the sample's physical state with the next digestive region it enters.
410. Examine the statements below about food capture and gastric digestion in a frog.
I. The bilobed tongue assists in capturing prey.
II. Hydrochloric acid acts in the stomach.
III. Gastric juice contributes to formation of partially digested chyme.
IV. Chyme moves directly from the mouth into the cloaca.
ⓐ. I is true; II is false; III is false; IV is true
ⓑ. I is false; II is true; III is false; IV is true
ⓒ. I is true; II is true; III is true; IV is false
ⓓ. I is true; II is true; III is true; IV is true
Correct Answer: I is true; II is true; III is true; IV is false
Explanation: The bilobed tongue functions at the ingestion stage and helps capture prey, making statement I valid. Acid and other gastric secretions act after food reaches the stomach, supporting statements II and III. Their action produces partially digested chyme, which then enters the duodenum. Statement IV bypasses the pharynx, oesophagus, stomach, intestine, and rectum and is incorrect. The cloaca is a terminal common chamber rather than the immediate destination of newly captured food. The valid combination preserves the progressive nature of digestion: capture occurs first, gastric chemical processing follows, and the partially digested material then proceeds into the intestinal region for further digestion and absorption. This order separates ingestion, conduction, gastric processing, and intestinal continuation into successive dependent stages.
411. Pair each digestive component with its principal action or destination. Each Column II entry is used once.
| Column I | Column II |
|---|
| P. Bile | W. Absorption of digested nutrients |
| Q. Pancreatic juice | X. Passage of undigested residue toward the cloaca |
| R. Villi and microvilli | Y. Emulsification of fats |
| S. Rectum | Z. Enzymatic digestion of carbohydrates and proteins |
ⓐ. P-Z, Q-Y, R-X, S-W
ⓑ. P-W, Q-X, R-Y, S-Z
ⓒ. P-X, Q-W, R-Z, S-Y
ⓓ. P-Y, Q-Z, R-W, S-X
Correct Answer: P-Y, Q-Z, R-W, S-X
Explanation: Bile emulsifies fats, so P matches Y. Pancreatic juice contains enzymes that act on carbohydrates and proteins, giving Q with Z. Villi and microvilli increase the intestinal surface available for absorption of digested nutrients, so R matches W. The rectum receives undigested residue from the intestine and conducts it toward the cloaca, linking S with X. These components act at different stages and through different mechanisms. Emulsification is a physical preparation of fat, enzymatic digestion breaks food molecules down chemically, absorption transfers usable products across the intestinal surface, and rectal passage handles material that remains. The complete mapping preserves this sequence of processing, uptake, and egestion. The matched functions occur at different digestive stages, from emulsification to absorption and elimination.
412. Assertion: Villi and microvilli improve absorption in the frog intestine.
Reason: Their projections increase the surface area available for digested nutrients to cross the intestinal lining.
ⓐ. Assertion is true; Reason is true; explanatory link is valid
ⓑ. Assertion is true; Reason is true; explanatory link is invalid
ⓒ. Assertion is true; Reason is false; explanatory link is invalid
ⓓ. Assertion is false; Reason is true; explanatory link is invalid
Correct Answer: Assertion is true; Reason is true; explanatory link is valid
Explanation: The assertion is valid because the intestinal lining is specialised for transferring digested nutrients into internal transport pathways. Villi form projections of the lining, and microvilli add still finer surface specialisation. Together they expose a greater area to the digested contents than a smooth surface of the same basic length would provide. A larger exchange area permits more nutrient molecules to contact absorptive cells at one time, improving the capacity for uptake. The reason states this geometrical structure-function relation and directly explains the assertion. The folds do not grind food or produce bile; their principal significance in this context is enhancement of absorption after digestion has produced small usable molecules.
413. Equal intestinal segments receive the same concentration of completely digested nutrients. Segment P retains normal villi and microvilli, while Segment Q has an equally permeable but experimentally flattened lining. Nutrient uptake is lower in Q. The strongest conclusion is:
ⓐ. digestive enzymes can act only on folded surfaces
ⓑ. the rectum is the principal site of nutrient absorption
ⓒ. microvilli transport undigested matter directly into the cloaca
ⓓ. increased intestinal surface area enhances absorption
Correct Answer: increased intestinal surface area enhances absorption
Explanation: Both segments receive the same nutrient concentration and retain comparable permeability, while the surface configuration is the major difference. Segment P possesses villi and microvilli, creating a larger area for contact between digested nutrients and absorptive cells. Flattening Segment Q reduces that area and is followed by lower uptake. The comparison supports a direct relation between surface enlargement and absorption. It does not test whether digestive enzymes require folds, since the nutrients are already completely digested. The rectum mainly handles undigested residue, and microvilli do not carry solid waste into the cloaca. Segment P retains normal villi and microvilli; this retained condition separates the immediate consequence from later secondary effects elsewhere in the organism. The conclusion remains focused on the measured variable: intestinal projections improve uptake by increasing available exchange area.
414. Which statement correctly distinguishes absorption from egestion in a frog?
ⓐ. Absorption is release of faeces, whereas egestion is entry of nutrients into villi
ⓑ. Absorption takes up digested nutrients, whereas egestion removes undigested matter
ⓒ. Absorption occurs only in the cloaca, whereas egestion occurs only in the stomach
ⓓ. Absorption and egestion are two names for bile secretion
Correct Answer: Absorption takes up digested nutrients, whereas egestion removes undigested matter
Explanation: Absorption occurs after digestion has converted food into small usable substances. These nutrients cross the intestinal lining, whose villi and microvilli provide a large absorptive surface, and enter internal transport pathways. Egestion concerns material that was not digested or absorbed. This residue passes through the rectum into the cloaca and leaves through the cloacal aperture. The two processes involve different materials, directions, and regions of the digestive pathway. Neither is equivalent to secretion of bile, and the stomach is not the terminal site of egestion. The distinction prevents a common confusion between uptake into the body and elimination of material that never became part of the body's nutrient pool. Absorption transfers useful molecules into internal transport, whereas egestion expels material that was not digested or absorbed.
415. The rectum of a frog is completely obstructed, but intestinal digestion and absorption remain initially normal. Which outcome is most likely?
ⓐ. Bile can no longer be produced by the liver
ⓑ. Pancreatic juice can no longer digest proteins
ⓒ. Prey can no longer be captured by the tongue
ⓓ. Residue accumulates before entering the cloaca
Correct Answer: Residue accumulates before entering the cloaca
Explanation: The rectum lies between the intestine and cloaca and receives material remaining after digestion and absorption. A complete obstruction prevents this residue from reaching the common terminal chamber, so accumulation occurs in the posterior digestive tract. Intestinal digestion and absorption remain initially normal, separating the blockage from earlier chemical and absorptive processes. The liver and pancreas can continue producing their secretions, and the tongue can still capture prey. Over time, accumulation may disturb other digestive functions, but the most direct effect is failure of residue passage from the rectum into the cloaca. The prediction follows the terminal sequence of the alimentary canal rather than assuming that every digestive stage stops simultaneously.
416. Examine the digestive records below.
| Record | Structure-function relation |
|---|
| P | Bilobed tongue captures prey |
| Q | Stomach produces partially digested chyme |
| R | Villi and microvilli increase nutrient absorption |
| S | Cloacal aperture transfers digested nutrients into blood |
The record requiring correction is:
ⓐ. Record S
ⓑ. Record P
ⓒ. Record Q
ⓓ. Record R
Correct Answer: Record S
Explanation: Records P, Q, and R preserve the major stages of the frog digestive process. The tongue captures prey, gastric secretions act in the stomach to produce partially digested chyme, and intestinal villi and microvilli increase the surface available for nutrient absorption. Record S assigns an absorptive role to the terminal external opening. The cloacal aperture releases material from the cloaca to the exterior; it does not transfer digested nutrients into the blood. Nutrient absorption occurs across the intestinal lining before undigested residue reaches the rectum and cloaca. Correcting S requires replacing its statement with the external discharge of cloacal contents. The table integrates ingestion, digestion, absorption, and egestion while identifying the single reversed structure-function relation.
417. Which comparison of respiratory modes in a frog is correct?
| Condition | Major respiratory surfaces involved |
|---|
| Water | Skin |
| Land | Buccal cavity, skin, and lungs |
| Aestivation or hibernation | Skin |
ⓐ. Only the water condition is correctly matched
ⓑ. All three conditions are correctly matched
ⓒ. Only the land condition is correctly matched
ⓓ. Only the dormant conditions are correctly matched
Correct Answer: All three conditions are correctly matched
Explanation: In water, the frog relies mainly on cutaneous respiration, with dissolved oxygen diffusing across the moist skin. On land, respiratory exchange is distributed among the moist buccal lining, skin, and lungs. During aestivation and hibernation, the frog remains inactive in shelter and depends mainly on cutaneous exchange rather than active pulmonary ventilation. The table preserves the condition-dependent nature of frog respiration. No single surface performs every respiratory role equally under all circumstances. The skin is the common component across the listed conditions, but the buccal cavity and lungs become particularly important during terrestrial activity. The rows must be compared by environmental condition, because the relative contribution of each respiratory surface changes between water, land, and dormancy. All three rows are biologically consistent.
418. A hibernating frog has intact lungs, but its skin becomes abnormally dry and nearly impermeable to respiratory gases. The most likely consequence is:
ⓐ. pulmonary respiration increases normally despite continued dormancy
ⓑ. the intestine becomes the principal respiratory organ
ⓒ. oxygen enters mainly through the tympana
ⓓ. cutaneous respiratory exchange declines during dormancy
Correct Answer: cutaneous respiratory exchange declines during dormancy
Explanation: During hibernation, the frog remains inactive and relies mainly on cutaneous respiration. The skin must remain moist and permeable so oxygen can dissolve at the surface and diffuse into underlying blood vessels. Drying and loss of permeability remove the principal exchange route available during the dormant state. The lungs may remain structurally intact, yet inactivity does not automatically produce the active ventilation needed to compensate fully. The intestine and tympana do not become respiratory organs under the stated condition. A hibernating frog has intact lungs; the intact component cannot fully replace the specialised role that has been lost. The predicted decline follows from matching the environmental state with its normal respiratory surface rather than assuming that any intact lung can replace the skin under every circumstance.
419. Assertion: A frog can exchange respiratory gases through its skin while submerged in water.
Reason: Dissolved oxygen can diffuse across the moist, vascular skin.
ⓐ. Assertion is true; Reason is true; explanatory link is valid
ⓑ. Assertion is true; Reason is true; explanatory link is invalid
ⓒ. Assertion is true; Reason is false; explanatory link is invalid
ⓓ. Assertion is false; Reason is true; explanatory link is invalid
Correct Answer: Assertion is true; Reason is true; explanatory link is valid
Explanation: The assertion is true since cutaneous respiration is the principal respiratory mode of a submerged frog. The reason is also true and states the mechanism that makes this possible. Oxygen dissolved in water reaches the moist skin surface, crosses the thin permeable boundary by diffusion, and enters blood vessels beneath the skin. Carbon dioxide can move in the opposite direction. The process does not require the frog to swallow water or fill its lungs with water. Dissolved oxygen can diffuse across the moist, vascular skin; the reason supplies both the relevant condition and the mechanism needed for the assertion. The reason directly explains how the skin can function as a respiratory surface in an aquatic condition and links moisture, dissolved gas, permeability, and vascular supply into one complete mechanism.
420. Four frogs are observed under different conditions.
| Case | Condition | Dominant observation |
|---|
| P | Submerged in water | Gas exchange continues across moist skin |
| Q | Active on land | Buccal, cutaneous, and pulmonary surfaces contribute |
| R | Aestivating in a burrow | Gas exchange continues mainly through skin |
| S | Active on land | Only the kidneys exchange respiratory gases |
Which case is biologically inconsistent?
ⓐ. Case P
ⓑ. Case Q
ⓒ. Case S
ⓓ. Case R
Correct Answer: Case S
Explanation: Cases P, Q, and R correctly reflect condition-dependent frog respiration. A submerged frog uses its moist skin for exchange with dissolved gases. An active terrestrial frog can use the buccal lining, skin, and lungs. During aestivation, reduced activity is supported mainly by cutaneous respiration. Case S is inconsistent because kidneys are excretory organs and do not replace the recognised respiratory surfaces during terrestrial activity. The error cannot be repaired by merely adding lungs to the same statement; the claim that only kidneys perform respiratory exchange is fundamentally incorrect. The comparison demonstrates that respiratory mode changes with environmental and activity conditions, while organ identity remains biologically fixed. A valid interpretation must preserve the recognised respiratory surfaces while allowing their relative contributions to change with conditions.
