Botany 2025 Paper I 50 marks Enumerate

Q2

(a) Enumerate the types of fruiting bodies of Ascomycota and Basidiomycota. Write the various steps of ascus formation in Ascomycetous members with suitable illustrations. 10+10=20 (b) What are the various modes of infection and dissemination of plant diseases caused by viruses ? Describe. 8+7=15 (c) Briefly describe the male and female strobili of Gnetum with suitable labelled diagrams. Why should you consider this plant a gymnosperm ? 10+5=15

हिंदी में प्रश्न पढ़ें

(a) ऐस्कोमाइकोटा और बेसिडियोमाइकोटा के फलकाय के प्रकारों का नामोल्लेख कीजिए । ऐस्कोमाइसीटीस सदस्यों में एक्स निर्माण के विभिन्न चरणों को उपयुक्त चित्रों के साथ लिखिए । 10+10=20 (b) विषाणुओं द्वारा उत्पन्न पादप रोगों के संक्रमण और प्रसार के विभिन्न तरीके क्या हैं ? विवरण दीजिए । 8+7=15 (c) उपयुक्त नामांकित आरेखों के साथ नीटम के नर और मादा शंकुओं का संक्षिप्त विवरण दीजिए । आपको इस पादप को अनावृतबीजी क्यों मानना चाहिए ? 10+5=15

Evaluate your answer to this question → See all 2025 Botany questions

Directive word: Enumerate

This question asks you to enumerate. 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 by enumerating the fruiting bodies of Ascomycota (ascocarps: apothecium, perithecium, cleistothecium) and Basidiomycota (basidiocarps: mushroom, bracket fungi, puffballs, stinkhorns) with clear hierarchical organization. For ascus formation, trace the sequential stages from ascogenous hyphae to crozier formation, nuclear fusion, meiosis, and ascospore delimitation with accurate diagrams. In part (b), systematically describe infection modes (mechanical, grafting, seed transmission, vectors) and dissemination (insect vectors like aphids/leafhoppers, nematodes, pollen, human agency) citing Indian crop examples like tungro virus of rice. For part (c), describe Gnetum strobili with emphasis on reduced nature and vessel presence, then justify gymnosperm status through naked ovules, absence of double fertilization, and endosperm development—allocate approximately 40% effort to (a), 30% each to (b) and (c) based on mark distribution.

Key points expected

  • Enumeration of ascocarp types (apothecium, perithecium, cleistothecium) with representative genera (Peziza, Neurospora, Penicillium) and basidiocarp types (agaric, polypore, puffball, clavarioid) with examples (Agaricus, Polyporus, Lycoperdon)
  • Stepwise ascus development: ascogenous hyphae → hook/crozier formation → dikaryon establishment → nuclear fusion (karyogamy) → meiosis I and II → mitosis → 8-nucleate stage → ascospore formation with wall delimitation
  • Virus infection modes: mechanical inoculation, graft transmission, seed and pollen transmission, dodder (Cuscuta) transmission, vector-mediated (aphids, leafhoppers, whiteflies, nematodes, fungi)
  • Virus dissemination mechanisms: insect vector specificity (non-persistent, semi-persistent, persistent), soil-borne nematodes, pollen and seed transmission, agricultural practices, international trade of infected planting material
  • Gnetum male strobilus: strobiloid inflorescence, decussate bracts, microsporangiophores with 2-3 microsporangia, prothallial cells in microspores; female strobilus: compound structure with outer envelope, nucellus, and micropylar tube
  • Gnetum as gymnosperm: naked ovules without ovary, single fertilization producing zygote and free-nuclear endosperm, absence of triple fusion, presence of archegonia (though reduced), tracheids with bordered pits alongside vessels

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness22%11Precise taxonomic classification of fruiting bodies; accurate terminology for ascus development stages (crozier, dikaryon, karyogamy); correct distinction between infection and dissemination; proper characterization of Gnetum reproductive structures with correct gymnosperm criteriaBasic classification present but some confusion between ascocarp types or basidiocarp forms; ascus stages described but sequence errors; virus modes listed but conflated; Gnetum structures described but gymnosperm justification weakMajor errors in fruiting body classification; fundamental misunderstanding of ascus development; confusion between infection and dissemination; incorrect assignment of Gnetum to angiosperms or major structural errors
Diagram / labelling20%10Clear labelled diagrams for ascus development stages (crozier, young ascus, mature ascus with ascospores), Gnetum male and female strobili with bracts, sporangiophores, and ovular structures; neat presentation with all parts identifiedDiagrams present but incomplete labelling or missing stages; Gnetum strobili drawn but lacking detail in internal structures; acceptable but not examination-quality illustrationsMissing diagrams for ascus formation or Gnetum structures; poorly drawn or unlabelled sketches; diagrams that misrepresent key structural relationships
Examples & nomenclature18%9Appropriate examples for each ascocarp type (Peziza, Xylaria, Erysiphe), basidiocarp types (Agaricus, Ganoderma, Geastrum); Indian virus examples (tungro virus, yellow vein mosaic of bhindi, banana bunchy top); correct binomials and family namesSome examples provided but generic or incorrect attribution; Indian crop viruses mentioned but not specifically identified; minor nomenclatural errorsNo specific examples or incorrect examples throughout; confusion between fungal groups; no mention of Indian agricultural context for viruses
Process explanation22%11Sequential, mechanistic explanation of ascus ontogeny with cellular events; detailed vector-virus transmission pathways (circulative vs. non-circulative); clear developmental sequence of Gnetum strobili with pollination drop mechanismProcesses described in correct order but lacking mechanistic detail; virus transmission described but without vector specificity; Gnetum development outlined but pollination biology omittedDisordered or incorrect sequence of developmental events; no explanation of how viruses move within vectors; missing critical developmental stages in Gnetum reproduction
Application / ecology18%9Ecological significance of fungal fruiting bodies (decomposition, mycorrhizae); economic impact of virus diseases on Indian agriculture with management implications; evolutionary significance of Gnetum's angiosperm-like features in gymnosperm contextBrief mention of ecological roles or agricultural importance without elaboration; Gnetum's evolutionary position noted but not integratedNo application or ecological context provided; purely descriptive answer without relevance to agriculture, forestry, or evolution

Practice this exact question

Write your answer, then get a detailed evaluation from our AI trained on UPSC's answer-writing standards. Free first evaluation — no signup needed to start.

Evaluate my answer →

More from Botany 2025 Paper I