Botany 2022 Paper II 50 marks Describe

Q8

(a) Define the terms photoperiodism and florigen. Describe the mechanism of response in short day and long day plants giving suitable examples. (20 marks) (b) Explain how the different greenhouse gases contribute to the raising global temperature. Add a note on the adverse effects of global warming and how to mitigate. (10+5=15 marks) (c) Describe the phytogeographical regions of India. What are the environmental factors that influence their species composition ? (10+5=15 marks)

हिंदी में प्रश्न पढ़ें

(a) दीप्तिकालिता और फ्लोरिजन शब्दावली को परिभाषित कीजिए । उपयुक्त उदाहरण देते हुए छोटे दिन और लम्बे दिन के पौधों में अनुक्रिया के तंत्र का वर्णन कीजिए । (20 अंक) (b) व्याख्या कीजिए कि विभिन्न हरितगृह गैसें वैश्विक तापमान को बढ़ाने में किस प्रकार योगदान करती हैं । ग्लोबल वार्मिंग के प्रतिकूल प्रभावों और इसे कम करने के तरीकों पर एक टिप्पणी लिखिये । (10+5=15 अंक) (c) भारत के पादप-भौगोलिक क्षेत्रों का वर्णन कीजिए । वे कौन से पर्यावरणीय कारक हैं जो उनकी प्रजातियों के संगठन को प्रभावित करते हैं ? (10+5=15 अंक)

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Directive word: Describe

This question asks you to describe. 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 'describe' demands detailed, structured exposition of mechanisms, regions and processes. Allocate approximately 40% of time/words to part (a) given its 20 marks, 30% each to parts (b) and (c). Structure: brief introduction linking plant physiology to climate-phytogeography nexus; body with three clearly demarcated sections using sub-headings; conclusion emphasizing integrated plant-environment relationships.

Key points expected

Part (a): Precise definitions of photoperiodism (Garner & Allard) and florigen (Chailakhyan); distinction between SDP (Chrysanthemum, rice) and LDP (wheat, barley) with critical day-length concept; phytochrome-mediated CO/FT gene regulation and mobile florigen (FT protein) transport
Part (b): Radiative forcing mechanisms of CO2, CH4, N2O, CFCs and H2O vapour with relative GWP values; Indian-specific impacts (Himalayan glacial retreat, monsoon variability, Sundarban submergence); mitigation strategies including INDCs, agroforestry and carbon sequestration
Part (c): Recognition of 10 phytogeographical regions (Champion & Seth classification) with characteristic vegetation types; Western Ghats vs Eastern Himalayas endemism; edaphic, climatic (temperature/rainfall gradients), topographic and anthropogenic factors shaping species composition
Integration: Link between photoperiodic adaptation and latitudinal distribution in phytogeographical regions; climate change impacts on flowering phenology and biome shifts
Critical evaluation: Limitations of florigen hypothesis, uncertainties in climate models, and challenges in phytogeographical boundary delineation

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	22%	11	Demonstrates flawless understanding across all parts: for (a) correctly distinguishes photoperiodism from vernalization, identifies phytochrome Pr/Pfr interconversion and FT protein as florigen; for (b) accurately explains molecular vibration-GHG absorption correlation and differentiates between natural and enhanced greenhouse effect; for (c) correctly identifies all 10 phytogeographical regions with their characteristic forest types	Shows basic conceptual grasp with minor errors: vague florigen description, conflates GWP with atmospheric lifetime, or misses 2-3 phytogeographical regions; some confusion between SDP/LDP mechanisms	Fundamental misconceptions: describes photoperiodism as response to light intensity, confuses greenhouse effect with ozone depletion, or lists only 3-4 phytogeographical regions with incorrect vegetation associations
Diagram / labelling	18%	9	Includes three high-quality diagrams: (a) phytochrome photoconversion with action spectra and/or florigen transport pathway from leaf to shoot apex; (b) greenhouse effect energy budget diagram showing incoming/outgoing radiation and absorption bands; (c) India map showing 10 phytogeographical regions with boundaries clearly marked; all fully labelled with scientific precision	Provides 2 diagrams with adequate labelling: basic photoperiodism flowchart, simple greenhouse effect sketch, or rough India map with 6-8 regions; missing some critical labels or arrows	Single diagram or poorly executed sketches; unlabelled or incorrectly labelled diagrams; no map for part (c); diagrams decorative rather than explanatory
Examples & nomenclature	20%	10	Rich, specific examples throughout: for (a) cites Xanthium (SDP), Hyoscyamus (LDP), and mentions Arabidopsis thaliana genetic studies; for (b) provides current CO2 levels (420+ ppm), methane from paddy fields, Indian specific data; for (c) names endemic genera (Dipterocarpus, Mesua) and correctly uses Champion & Seth nomenclature (1A/2B/C1 etc.)	Generic examples: mentions rice/wheat without species names, lists common GHGs without Indian context, identifies 5-6 regions with standard examples; some nomenclature errors	Few or incorrect examples: confuses SDP/LDP examples, no Indian-specific climate data, vague 'tropical forests' without regional specificity; major nomenclature errors in classification
Process explanation	22%	11	Mechanistic depth across all parts: (a) explains circadian clock-phytochrome interaction, CO protein stabilization, FT transcription and phloem transport; (b) details vibrational-rotational energy states, atmospheric window, feedback loops; (c) explains species-area relationship, Rapoport's rule application to Indian gradients, and disturbance ecology	Describes processes in sequence but lacks mechanistic detail: states 'long night induces flowering' without phytochrome mechanism, lists GHG properties without radiative forcing explanation, describes regions without ecological processes	Descriptive only, no process: lists plant types without mechanism, states 'gases trap heat' without explanation, enumerates regions like a gazetteer without ecological reasoning
Application / ecology	18%	9	Demonstrates sophisticated applied understanding: (a) discusses photoperiodic manipulation in floriculture (Chrysanthemum year-round flowering) and crop breeding; (b) analyzes India's NDC commitments, agroecosystem vulnerability, climate-smart agriculture; (c) evaluates hotspot conservation priorities, corridor connectivity, and projected biome shifts under climate change scenarios	Some applied content: mentions commercial applications briefly, lists mitigation strategies without evaluation, notes conservation importance of regions without prioritization framework	Purely theoretical with no application: no mention of agriculture/horticulture relevance, no Indian policy context, no conservation implications; fails to integrate across the three sub-parts

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