Zoology 2022 Paper II 50 marks 150 words Compulsory Explain

Q5

Write your answer in about 150 words for each of the following : 10×5=50 (a) Define immunity. Explain cell-mediated immune response in vertebrates with suitable diagram. (b) Describe the structure and functions of mammalian placenta. (c) Explain the functions of neutrophils, basophils and lymphocytes. (d) Illustrate the counter-current mechanism by vasa recta and mention its physiological importance. (e) Define biogenetic law. Write the characteristics of Haeckel's theory of recapitulation.

हिंदी में प्रश्न पढ़ें

निम्नलिखित प्रत्येक के लिए लगभग 150 शब्दों में अपना उत्तर लिखिए : 10×5=50 (a) प्रतिरक्षा को परिभाषित कीजिए। उपयुक्त आरेख के साथ कशेरुकियों में कोशिका-माध्यित प्रतिरक्षा अनुक्रिया की व्याख्या कीजिए। (b) स्तनधारी अपरा की संरचना तथा कार्यों का वर्णन कीजिए। (c) न्यूट्रोफिल, बेसोफिल तथा लिम्फोसाइट के कार्यों की व्याख्या कीजिए। (d) वासा रेक्टा के प्रतिधारा तंत्र का सचित्र विवरण दीजिए, तथा उसके कार्यिकीय महत्व का उल्लेख कीजिए। (e) बायोजेनेटिक नियम को परिभाषित कीजिए। पुनरावृत्ति के हैकल सिद्धांत की विशेषताएं लिखिए।

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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

Begin with precise definitions for (a) and (e), then explain mechanisms for (a), (c), and (d) using sequential logic. For (b), adopt a structure-function integrated approach. Allocate ~30 words per sub-part (150 total), prioritizing diagram quality for (a) and (d). Use bullet points for clarity across all five parts, ensuring each sub-answer is self-contained.

Key points expected

(a) Definition of immunity (innate vs. adaptive); cell-mediated response via T-cells (Th, Tc, Treg); diagram showing antigen presentation → T-cell activation → cytotoxic action
(b) Placental structure: chorionic villi, decidua basalis, maternal/foetal circulation; functions: nutrient/gas exchange, hormone secretion (hCG, progesterone), immunological barrier
(c) Neutrophils (phagocytosis, NETs), basophils (histamine release, allergic response), lymphocytes (B-cells: antibody production; T-cells: cellular immunity; NK cells: innate cytotoxicity)
(d) Counter-current multiplier in vasa recta: parallel flow of descending/ascending limbs; maintenance of medullary osmotic gradient; importance: urine concentration, water conservation
(e) Biogenetic law definition: 'ontogeny recapitulates phylogeny'; Haeckel's theory characteristics: developmental stages mirror evolutionary history; criticisms (von Baer's laws, modern evo-devo evidence)

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	25%	12.5	Accurately defines immunity as specific/non-specific defense; correctly identifies T-cell subsets in (a); distinguishes haemochorial placenta in (b); classifies lymphocyte types precisely in (c); explains osmotic gradient mechanics in (d); states biogenetic law with proper attribution in (e)	Basic definitions correct but conflates humoral/cell-mediated immunity; placenta description lacks circulatory detail; lymphocyte functions partially accurate; counter-current described without osmolarity values; recapitulation stated without Haeckel's name	Confuses immunity with resistance; omits T-cell activation steps; describes placenta as mere 'connection'; mixes granulocyte functions; describes vasa recta as 'blood vessel in kidney' only; biogenetic law garbled or omitted
Diagram / labelling	20%	10	Two clear diagrams: (a) shows APC-T cell interaction with MHC-TCR binding, cytokine signaling; (d) depicts parallel vasa recta with descending (arterial) and ascending (venous) limbs, osmolarity gradient (300-1200 mOsm) indicated; neat labelling with arrows	One acceptable diagram with partial labelling; (a) shows T-cells without activation cascade; (d) shows loop but lacks flow direction or concentration gradient; handwriting legible but crowded	Diagrams absent or unrecognizable; stick figures for cells; no directional arrows; labels missing or incorrect; (d) confused with counter-current in fish gills
Examples & nomenclature	15%	7.5	Uses precise terms: CD4+/CD8+ T-cells, MHC-I/II, syncytiotrophoblast, hCG, diapedesis, phagosome/lysosome fusion, juxtamedullary nephrons; cites Indian mammal examples (human haemochorial, bovine epitheliochorial for comparison)	Generic terms like 'white blood cells' instead of leukocyte subsets; 'placental barrier' without layers named; 'kidney tube' for nephron; no species examples	Misnomers: 'antibodies' for cell-mediated response; 'umbilical cord' for placenta; 'basophils fight bacteria' (incorrect); 'veins' for vasa recta; 'Haeckel's evolution theory' confused with Darwin
Process explanation	25%	12.5	(a) Sequential: antigen processing → presentation → clonal expansion → effector function (perforin/granzyme pathway); (c) Stepwise phagocytosis in neutrophils, degranulation in basophils, clonal selection in lymphocytes; (d) Quantitative osmotic gradient buildup explained	Processes mentioned but not sequenced; cell-mediated response lacks activation details; placenta exchange described passively; lymphocyte functions listed without mechanism; counter-current stated without 'multiplier' concept	No process logic; random fact listing; cell-mediated immunity described as 'T-cells attack'; placenta 'gives food to baby'; vasa recta 'cools blood'; no developmental sequence in (e)
Evolutionary / applied context	15%	7.5	(e) Critically evaluates Haeckel: acknowledges historical significance but notes falsified embryo drawings, von Baer's alternative (development from general to specific); connects to modern evo-devo (Hox genes); (a) notes MHC polymorphism and pathogen evasion; (d) links to desert adaptation (camel, Indian desert rodents)	Mentions recapitulation uncritically; no connection to contemporary immunology or physiology; generic 'important for survival' statements	Treats Haeckel as established fact; no evolutionary context for immunity or renal function; completely misses applied significance of any sub-part

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