Zoology 2023 Paper I 50 marks 150 words Compulsory Write short notes

Q5

Write short notes on the following in about 150 words each: (a) Ecological niche (10 marks) (b) Instinct behaviour in animals (10 marks) (c) Pathogenesis of cholera (10 marks) (d) Amniocentesis (10 marks) (e) Lotka-Volterra model (10 marks)

हिंदी में प्रश्न पढ़ें

निम्नलिखित में से प्रत्येक पर 150 शब्दों में संक्षिप्त टिप्पणी लिखिए : (a) पारिस्थितिक निकेत (10 अंक) (b) प्राणियों में सहज व्यवहार (10 अंक) (c) हैजा का रोगजनन (10 अंक) (d) उल्बवेधन (10 अंक) (e) लोटका-वोल्टेरा मॉडल (10 अंक)

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Directive word: Write short notes

This question asks you to write short notes. 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 'write short notes' demands concise, information-dense responses for each sub-part. Allocate approximately 30 words per mark (150 words × 5 parts = 750 total). Spend roughly equal time on each part (10 marks each), prioritizing precise definitions, key mechanisms, and one illustrative example per sub-part. Structure each note as: definition → core mechanism/process → specific example/application → brief significance.

Key points expected

(a) Ecological niche: Define Hutchinson's n-dimensional hypervolume; distinguish fundamental vs. realized niche; cite Indian example (e.g., lion-tailed macaque in Western Ghats canopy niche)
(b) Instinct behaviour: Define as innate, stereotyped, unlearned; mention fixed action patterns (FAPs), sign stimuli; cite classic example (Tinbergen's stickleback aggression or herring gull egg-retrieval)
(c) Pathogenesis of cholera: Vibrio cholerae O1/O139 → mucosal adherence → CT toxin (ctxAB genes) → ADP-ribosylation of Gs protein → cAMP elevation → Cl⁻/HCO₃⁻ efflux → massive watery diarrhea; mention rice-water stool
(d) Amniocentesis: 15-20 weeks gestation → ultrasound-guided needle aspiration → karyotyping/biochemical analysis; indicate diagnostic scope (aneuploidy, neural tube defects) and ethical/legal context (PCPNDT Act in India)
(e) Lotka-Volterra model: Predator-prey coupled differential equations; describe oscillatory population dynamics, isoclines, stable equilibrium; mention assumptions and limitations

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	20%	10	For (a), correctly distinguishes fundamental/realized niche with Hutchinson's formalism; for (b), accurately defines FAPs and sign stimuli; for (c), precisely describes CT toxin mechanism including Gs protein modification; for (d), states correct gestational window and diagnostic capabilities; for (e), writes correct Lotka-Volterra equations or accurately describes their biological interpretation	Provides generally correct definitions with minor errors (e.g., conflates niche with habitat, omits Gs protein in cholera mechanism, vague on amniocentesis timing); shows basic grasp without precision	Fundamental misconceptions (e.g., describes learned behavior as instinct, wrong toxin mechanism, amniocentesis confused with chorionic villus sampling, predator-prey relationships reversed in model)
Diagram / labelling	20%	10	Includes at least 2-3 quick sketches: for (a) niche dimensionality or overlap diagram; for (c) cholera toxin mechanism or ion transport; for (e) predator-prey oscillation graph or isocline plot; all properly labelled with axes and key components	Includes one diagram (typically for Lotka-Volterra) with basic labelling; or attempts diagrams with missing labels/unclear axes; describes others verbally only	No diagrams despite visual potential in multiple parts; or diagrams present but completely unlabelled, misleading, or irrelevant to the specific sub-part
Examples & nomenclature	20%	10	Uses precise scientific nomenclature throughout: Vibrio cholerae O1/O139, ctxAB, Gsα, ADP-ribosylation; cites specific researchers (Hutchinson, Tinbergen, Lotka, Volterra) or classic studies; includes Indian context (PCPNDT Act, endemic cholera regions, Indian wildlife examples)	Uses common names or generic descriptions; mentions one researcher or Indian example; basic terminology present but lacks specificity (e.g., 'cholera bacteria' instead of V. cholerae, 'predator-prey model' without names)	No specific examples; incorrect nomenclature (e.g., 'amniotic fluid test' instead of amniocentesis); no citation of researchers; completely generic descriptions without scientific terms
Process explanation	20%	10	For (c), clearly sequences toxin entry → B subunit binding → A subunit activation → cAMP cascade → CFTR channel opening → secretory diarrhea; for (e), explains how predator and prey equations interact to produce coupled oscillations; for (d), outlines procedural steps chronologically; all processes logically ordered with causal connectors	Describes processes in correct general order but misses key intermediate steps (e.g., omits cAMP in cholera, describes oscillations without explaining mechanism); some logical gaps in sequencing	Processes jumbled or reversed (e.g., diarrhea before toxin action); no clear causal chain; describes outcomes without mechanisms; conflates different procedures (amniocentesis vs. CVS)
Evolutionary / applied context	20%	10	For (a), mentions competitive exclusion and niche partitioning as evolutionary outcomes; for (b), contrasts instinct with learning, notes adaptive value of FAPs; for (c), notes selective pressure for toxin production, vaccine development (oral rehydration/WHO strategy); for (d), addresses ethical implications, sex-selective abortion concerns, PCPNDT Act; for (e), discusses model's predictive value in fisheries/wildlife management	Briefly notes one applied aspect per relevant sub-part (e.g., mentions ORS for cholera, or ethical issue for amniocentesis) without elaboration; evolutionary context superficial or missing for instinct/niche	No applied or evolutionary context; treats all topics as purely descriptive; ignores ethical dimensions where clearly relevant; no mention of conservation, medical, or policy implications

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