Botany 2024 Paper I 50 marks Describe

Q2

(a) Describe the five distinct stages in the life cycle of Puccinia graminis with suitable diagrams. 20 (b) With suitable examples, bring out the industrial uses of microorganisms. What are the advantages of using immobilised enzymes and cells in commercial processes? 10+5=15 (c) Why is Ginkgo biloba called a 'living fossil'? Discuss in the light of its reproductive structures. 5+10=15

हिंदी में प्रश्न पढ़ें

(a) पक्सिनिया ग्रैमिनिस के जीवनचक्र में पाँच विशिष्ट चरणों का उपयुक्त चित्रों सहित वर्णन कीजिए। 20 (b) उपयुक्त उदाहरणों सहित सूक्ष्मजीवों के औद्योगिक उपयोगों को उजागर कीजिए। वाणिज्यिक प्रक्रियाओं में स्थिर एंजाइमों और कोशिकाओं का उपयोग करने के क्या-क्या लाभ हैं? 10+5=15 (c) जिन्को बाइलोबा को 'जीवित जीवाश्म' क्यों कहा जाता है? इसकी चर्चा प्रजनन संरचनाओं के आधार पर कीजिए। 5+10=15

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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, systematic exposition of structures, processes and phenomena. Allocate approximately 40% of time/words to part (a) given its 20 marks, covering all five spore stages with clear diagrams; 30% each to parts (b) and (c). Structure: brief introduction on fungal pathogens and living fossils → systematic treatment of each sub-part with diagrams for (a) and (c) → concluding synthesis on evolutionary significance and biotechnological applications.

Key points expected

  • Part (a): Five stages of Puccinia graminis — uredospores (uredinial stage on wheat), teleutospores (telial stage), basidiospores (basidial stage on barberry), pycniospores (pycnial stage), and aeciospores (aecial stage); heteroecious and macrocyclic nature
  • Part (b): Industrial uses — fermentation (ethanol by Saccharomyces cerevisiae), antibiotics (penicillin by Penicillium chrysogenum), enzymes (amylase, protease), biofertilizers (Rhizobium, Azotobacter), and single cell protein; advantages of immobilisation — reusability, stability, continuous operation, cost reduction
  • Part (c): 'Living fossil' criteria — morphological stasis since Mesozoic, sole extant species in Ginkgophyta; reproductive structures — motile male gametes (antherozoids), absence of ovary, naked ovules, fertilisation in archegonial chamber, dichotomous venation
  • Diagrammatic requirements: Life cycle diagram of Puccinia showing host alternation (wheat-barberry), spore types with pedicel characteristics; Ginkgo ovule and male strobilus structure
  • Scientific nomenclature: Correct binomials (Puccinia graminis tritici, Triticum aestivum, Berberis vulgaris, Ginkgo biloba), spore terminology (teliospores not teleutospores acceptable if consistent)

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness22%11Accurately identifies all five spore stages with correct ploidy levels (n, 2n) and host associations; correctly distinguishes autoecious vs heteroecious rusts; accurately describes Ginkgo's primitive features (ciliated sperm, archegonia) and their evolutionary significance; immobilisation advantages linked to enzyme kinetics and industrial economicsIdentifies major stages but confuses ploidy or host alternation; describes Ginkgo features without linking to 'living fossil' concept; lists immobilisation advantages without mechanistic explanationConfuses spore stages (e.g., aecia with uredia), omits host alternation entirely; describes Ginkgo as 'ancient tree' without reproductive details; misunderstands immobilisation as mere enzyme extraction
Diagram / labelling20%10Clear, labelled diagrams for Puccinia life cycle showing wheat and barberry stages with spore morphology (pedicellate teliospores, cup-shaped aecia); Ginkgo ovule longitudinal section showing micropyle, integument, nucellus and archegonial chamber; neat, exam-appropriate sketches with arrows indicating sequenceDiagrams present but incomplete labelling or missing one host; Ginkgo diagram shows leaf but not reproductive structures; basic spore shapes without structural detailsNo diagrams or unrecognisable sketches; labels missing or incorrect; confuses Puccinia with other rust genera; substitutes textual description for required illustrations
Examples & nomenclature18%9Precise binomial nomenclature throughout (Puccinia graminis f. sp. tritici, Saccharomyces cerevisiae, Penicillium chrysogenum, Ginkgo biloba); specific Indian/industrial examples (streptomycin from Streptomyces griseus, citric acid from Aspergillus niger, biopesticide Bacillus thuringiensis); correct spore terminology (basidiospores, not basidiospores)Generic genus names without species; common examples (yeast for alcohol, penicillin) without specifying organisms; minor nomenclature errors (Ginko for Ginkgo)Incorrect or invented scientific names; no specific industrial organisms named; vernacular names only (wheat rust, maidenhair tree without Ginkgo biloba)
Process explanation22%11Clear sequential explanation of dikaryophase maintenance in Puccinia; explains spermatisation and dikaryotisation in pycnial stage; describes chemotaxis of Ginkgo spermatozoids; details immobilisation techniques (entrapment, covalent bonding, adsorption) with specific applications (glucose isomerase for high-fructose corn syrup)Lists stages chronologically but misses nuclear condition changes; describes Ginkgo reproduction without flagellated sperm mechanism; mentions immobilisation without technique differentiationRandom or incorrect stage ordering; no explanation of nuclear phases; confuses sexual and asexual stages; describes free enzymes as immobilised
Application / ecology18%9Links Puccinia to wheat rust epidemiology and breeding for resistance (Sr genes); discusses Ginkgo's ecological resilience (pollution tolerance, insect resistance) explaining survival; evaluates immobilised cell systems for secondary metabolite production (plant cell cultures, steroid biotransformation); mentions Indian initiatives (NCL Pune enzyme technology)Mentions crop loss due to rust without resistance strategies; notes Ginkgo's survival without ecological explanation; lists immobilisation applications without evaluationNo application context; treats all three topics as purely academic; ignores agricultural or industrial significance entirely

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