Botany 2025 Paper II 50 marks Discuss

Q6

(a) What are transgenic crops? Discuss the prospects and risks involved in their cultivation. (20 marks) (b) What is biological nitrogen fixation? Explain the mechanism of symbiotic nitrogen fixation with examples. (15 marks) (c) Describe the different forest types in India. Discuss in detail the crucial ecosystem services provided by these forests. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) ट्रांसजेनिक फसलें क्या हैं? उनकी खेती में शामिल संभावनाओं तथा जोखिमों पर चर्चा कीजिए। (20 अंक) (b) जैविक नाइट्रोजन स्थिरीकरण क्या है? सहजीवी नाइट्रोजन स्थिरीकरण की प्रक्रिया को उदाहरण सहित समझाइए। (15 अंक) (c) भारत में विभिन्न वन प्रकारों का वर्णन कीजिए। इन वनों द्वारा प्रदान की गई महत्वपूर्ण पारितंत्र सेवाओं की विस्तारपूर्वक विवेचना कीजिए। (15 अंक)

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Directive word: Discuss

This question asks you to discuss. 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 'discuss' demands a balanced, analytical treatment with arguments for and against. Structure: Introduction defining transgenic crops and BNF; Body—spend ~40% word/time on part (a) given 20 marks, covering prospects and risks with evidence; ~30% each on (b) and (c), with (b) detailing nif gene regulation and nodulation, and (c) classifying forests by Champion & Seth and linking services to climate regulation; Conclusion synthesizing biotechnology-ecology interface for sustainable agriculture.

Key points expected

  • Part (a): Definition of transgenic crops (rDNA technology, cisgenic vs transgenic); prospects—yield stability, biofortification (Golden Rice), pest resistance (Bt cotton, Bt brinjal), herbicide tolerance, climate resilience; risks—gene flow to wild relatives, development of resistance (pink bollworm in Bt cotton), non-target effects on pollinators, allergenicity concerns, IPR issues, farmer dependency
  • Part (b): Definition of BNF vs industrial fixation; mechanism—recognition (flavonoid-nod factor signaling), infection thread formation, nodule organogenesis, bacteroid differentiation, nitrogenase complex (Mo-Fe protein, Fe protein), leghaemoglobin function, ammonia assimilation (GS-GOGAT); examples—Rhizobium-legume (Glycine max, Cajanus cajan), Frankia-actinorhizal (Casuarina, Alnus), Anabaena-Azolla symbiosis
  • Part (c): Forest classification by Champion & Seth—Tropical Wet Evergreen, Semi-Evergreen, Moist Deciduous, Dry Deciduous, Thorn, Littoral & Swamp, Alpine; ecosystem services—carbon sequestration (Western Ghats as carbon sink), watershed protection (Himalayan forests), biodiversity hotspot value, soil conservation, pollination services, NTFPs for livelihoods, cultural services
  • Integration: Link transgenic crops to reduced fertilizer need via BNF potential; connect forest ecosystem services to agricultural sustainability and climate adaptation
  • Critical perspective: Mention regulatory frameworks—GEAC approval process, Cartagena Protocol, Nagoya Protocol; forest policy evolution from 1952 to 1988 and NAPCC relevance

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness20%10Precise definitions across all parts: transgenic vs conventional breeding, cisgenesis; accurate distinction between BNF, associative and free-living fixation; correct forest typology following Champion & Seth; no conflation of nitrogenase with nitrate reductaseBroadly correct definitions with minor errors—e.g., vague on rDNA mechanism, conflates all legume symbioses as Rhizobium without mentioning Bradyrhizobium or Sinorhizobium; forest types listed but misclassifiedFundamental errors—defines transgenic as hybridization, describes nitrogen fixation as root absorption, confuses tropical moist and dry deciduous forests, or invents non-existent categories
Diagram / labelling15%7.5Clear, labeled diagrams for at least two parts: T-DNA transfer mechanism in Agrobacterium-mediated transformation OR gene gun method; detailed legume root nodule cross-section showing infection thread, bacteroid zone, meristem, vascular connection; forest zonation diagram or ecosystem service flow diagramOne relevant diagram with partial labeling—e.g., nodule structure without distinguishing cortex from infected zone, or simple Bt gene insertion sketch without promoter/terminator labelsNo diagrams, or irrelevant sketches; poorly labeled diagrams that misrepresent anatomical relationships or molecular mechanisms
Examples & nomenclature20%10Specific Indian examples: Bt cotton (MECH-162, RCH-2 events), GM mustard (DMH-11), Golden Rice; Rhizobium meliloti-Medicago, Bradyrhizobium japonicum-Glycine max, Frankia-Casuarina equisetifolia; forest examples—Silent Valley (evergreen), Gir (dry deciduous), Sundarbans (littoral); cites GEAC, CPRI, NBPGRGeneric examples—mentions 'Bt crops' without specificity, 'legumes' without naming genera, 'tropical forests' without location; some nomenclature errors like 'Rhizobium' for all symbiontsNo Indian examples, incorrect nomenclature (e.g., Azotobacter for symbiotic fixation), fictional institutions, or irrelevant international examples without Indian context
Process explanation25%12.5Detailed mechanistic explanations: for (a) gene silencing, RNAi, site-directed nucleases; for (b) nod gene induction, NodD protein, calcium spiking, ENOD gene expression, oxygen protection by leghaemoglobin, ammonium export; for (c) successional dynamics linking forest types to rainfall gradients and edaphic factorsSequential but superficial—lists steps without molecular detail; describes nodule formation as 'bacteria enter roots' without infection thread mechanism; forest distribution by rainfall without explaining soil-vegetation feedbacksDescriptive only, no process logic; confuses cause and effect; incorrect sequence of molecular events; treats forest types as arbitrary categories without ecological basis
Application / ecology20%10Integrative ecological thinking: for (a) discusses gene flow to wild Brassica relatives, impact on non-target Lepidoptera, refuge strategy for resistance management; for (b) explains inoculant technology, biofertilizer limitations, BNF as alternative to urea subsidy burden; for (c) quantifies services—Western Ghats as 30% of India's carbon stock, Himalayan forests as 'water towers', links to REDD+ and India's NDCsLists applications without critical evaluation—mentions 'Bt cotton success' without noting regional variation or farmer suicide debates; describes forests as 'important' without specific service quantification; generic sustainability claimsNo application dimension; purely theoretical treatment; ignores ecological consequences entirely; or makes unsupported claims about GMO safety/forest restoration without evidence

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