Zoology 2021 Paper II 50 marks Explain

Q7

(a) Explain the basic stimuli causing pancreatic secretion. Discuss the role of pancreas in major food digestion. 20 (b) Explain the transport of oxygen in blood. Discuss the factors that shift oxygen-hemoglobin dissociation curve. 15 (c) Describe the functional anatomy of cochlea with suitable diagram. Write down the functions of organ of corti. 15

हिंदी में प्रश्न पढ़ें

(a) अग्न्याशय स्राव पैदा करने वाले मूल उद्दीपनों की व्याख्या कीजिए । प्रमुख खाद्य पाचन में अग्न्याशय की भूमिका की विवेचना कीजिए । 20 (b) रक्त में आक्सीजन के परिवहन की व्याख्या कीजिए । आक्सीजन-हीमोग्लोबिन विमोजन वक्र को स्थानान्तरित करने वाले कारकों की विवेचना कीजिए । 15 (c) कर्णवर्त (कॉक्लिया) की प्रकार्यात्मक शरीर रचना का उपयुक्त आरेख के साथ वर्णन कीजिए । कॉर्टी अंग के कार्यों को स्पष्ट कीजिए । 15

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Directive word: Explain

This question asks you to explain. The directive word signals the depth of analysis expected, the structure of your answer, and the weight of evidence you must bring.

See our UPSC directive words guide for a full breakdown of how to respond to each command word.

How this answer will be evaluated

Approach

The directive 'explain' demands clear causal reasoning and mechanistic detail across all three parts. Allocate approximately 40% of word budget to part (a) given its 20 marks, with ~30% each to parts (b) and (c). Structure with brief introductions for each sub-part, followed by systematic exposition of mechanisms, and conclude with integrated physiological significance. For part (c), dedicate sufficient space to a well-labelled diagram of cochlear structure.

Key points expected

Part (a): Neural (vagal) and hormonal (secretin, CCK) stimuli for pancreatic secretion; acinar cell secretion of enzymes (amylase, lipase, proteases) and duct cell bicarbonate secretion
Part (a): Pancreatic role in carbohydrate, protein and lipid digestion with specific enzyme mechanisms
Part (b): Oxygen transport as oxyhemoglobin (98.5%) and dissolved plasma (1.5%); hemoglobin structure (4 heme groups, cooperative binding)
Part (b): Bohr effect, temperature, 2,3-BPG, pCO2 and pH effects on ODC shift with physiological significance
Part (c): Cochlear structure showing scala vestibuli, scala media, scala tympani, basilar membrane, and helicotrema
Part (c): Organ of Corti with hair cells (inner and outer), tectorial membrane, and functions in mechanotransduction and frequency discrimination

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	25%	12.5	Accurately describes cephalic, gastric and intestinal phases of pancreatic regulation; correctly states Haldane and Bohr effects; precisely identifies cochlear structures and tonotopic organization with no factual errors across all three parts	Generally correct but minor errors in hormone targets (e.g., confusing secretin vs. CCK action), oversimplified ODC explanations, or incomplete cochlear anatomy	Major conceptual errors such as stating pancreas is only exocrine, confusing oxygen transport mechanisms, or fundamental misunderstanding of cochlear fluid compartments
Diagram / labelling	15%	7.5	Clear, proportionate diagram of cochlea in part (c) showing cross-section with scala vestibuli/media/tympani, vestibular and tympanic ducts, and detailed Organ of Corti inset; optional supporting sketches for ODC or pancreatic acinus enhance clarity	Basic cochlear diagram present but missing key labels (e.g., helicotrema or specific scalae) or disproportionate representation; diagram supports but does not substantially enhance answer	No diagram for part (c), or diagram with major structural errors (e.g., single chamber cochlea, missing basilar membrane); diagrams for other parts absent where they would aid explanation
Examples & nomenclature	15%	7.5	Precise terminology: acinus vs. islet, zymogen activation, P50 values, 2,3-bisphosphoglycerate, inner vs. outer hair cells, reticular lamina; cites comparative physiological data (e.g., human vs. high-altitude adapted species for ODC)	Generally correct nomenclature but occasional imprecision (e.g., 'pancreatic juice' without specifying enzyme vs. bicarbonate components; 'hair cells' without inner/outer distinction)	Incorrect or missing terminology (e.g., 'pancreatic acid', confusing oxyhemoglobin with carboxyhemoglobin, 'cochlear nerve' without specifying vestibulocochlear divisions)
Process explanation	25%	12.5	Stepwise mechanistic clarity: stimulus-secretion coupling in pancreatic acinar cells (IP3/Ca2+ pathway), cooperative binding kinetics and sigmoid curve mathematics, mechanical-to-electrical transduction in hair cells with tip-link mechanism; shows causal chains throughout	Describes processes in correct sequence but lacks mechanistic depth (e.g., states 'enzymes are released' without exocytosis mechanism; describes ODC shifts without molecular explanation; hair cell depolarization without stereocilia mechanism)	Descriptive only without process logic; lists structures or factors without explaining how they function; confused temporal sequences (e.g., stating CCK releases secretin)
Evolutionary / applied context	20%	10	Integrates clinical/applied significance: pancreatic insufficiency and cystic fibrosis, fetal hemoglobin left-shift advantage, high-altitude adaptation and athletic performance, noise-induced hearing loss and cochlear implant technology; references Indian context (e.g., high-altitude populations in Ladakh/Himalayas)	Brief mention of applied relevance (e.g., 'important in disease') without elaboration; or isolated example without integration across parts	No applied or evolutionary context; answer remains purely descriptive without addressing why these mechanisms matter physiologically or clinically

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