Botany 2022 Paper I 50 marks 150 words Compulsory Describe

Q1

Answer the following in about 150 words each : 10×5=50 (a) What is mycoplasma? Describe its types and importance in plant pathogenesis. 2+8=10 (b) Describe the ultrastructure of endospore of Bacillus sp. (c) Describe the structure of strobilus of Equisetum with the help of a well-labelled diagram. (d) What is chloroplast? Describe the fine structure of chloroplast in Chlorophyceae. (e) Write a comparative account of the icosahedral and helical symmetry of viruses.

हिंदी में प्रश्न पढ़ें

निम्नलिखित में से प्रत्येक का लगभग 150 शब्दों में उत्तर दीजिए : 10×5=50 (a) कवकद्रव्य (माइकोप्लाज्मा) क्या है? उसके प्रकार एवं पादप रोगजनन में उसके महत्व का वर्णन कीजिए। 2+8=10 (b) दंडाणु (बैसिलस) जाति के अंतर्बीजाणु (एंडोस्पोर) की अतिसूक्ष्म संरचना की व्याख्या कीजिए। (c) एक सुचिहित चित्र की सहायता से इक्विसीटम के शंकु (स्ट्रोबिलस) की संरचना का वर्णन कीजिए। (d) हरितलवक (क्लोरोप्लास्ट) क्या है? क्लोरोफाइसी के हरितलवक की सूक्ष्म संरचना का वर्णन कीजिए। (e) विषाणुओं की विषफलकीय (आइकोसाहेड्रल) एवं कुंडलीय (हेलिकल) सममिति का एक तुलनात्मक विवरण लिखिए।

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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 precise structural and functional detailing across all five sub-parts. Allocate approximately 30 words to part (a) given its 10-mark weight, and 30 words each to parts (b)-(e). Structure each answer as: definition/identification → structural components → functional significance. For part (c), prioritize the diagram within the word limit. Avoid lengthy introductions; move directly to descriptive content.

Key points expected

(a) Define mycoplasma as wall-less prokaryotes; distinguish Acholeplasmataceae from Spiroplasmataceae; cite phytoplasmas causing little leaf of brinjal or sandal spike disease in India
(b) Detail endospore layers: exosporium, spore coat, cortex, core wall, inner membrane; mention dipicolinic acid and calcium complex; note core dehydration and SASPs
(c) Draw vertical section of strobilus showing sporangiophores, sporangia, elaters, spores; indicate compact arrangement and peltate shield-like appendages
(d) Define chloroplast as double-membraned organelle; describe thylakoid arrangement (stacked/unstacked), pyrenoids, starch sheath in Chlorophyceae like Chlamydomonas or Spirogyra
(e) Contrast icosahedral (20 triangular faces, 12 vertices, 5-3-2 symmetry) with helical (protein subunits in helical array, hollow tube); cite TMV (helical) and Adenovirus/Cauliflower mosaic virus (icosahedral)

Evaluation rubric

Dimension	Weight	Max marks	Excellent	Average	Poor
Concept correctness	25%	12.5	Accurately defines all five biological entities; correctly identifies mycoplasma as Mollicutes without cell wall; precisely describes endospore ultrastructure with correct layer sequence; accurately portrays strobilus as compact terminal structure; correctly notes thylakoid arrangement in Chlorophyceae; properly distinguishes viral symmetry types by capsid geometry	Defines most entities correctly but confuses some structural details (e.g., misorders endospore layers or conflates strobilus with sporangium); minor errors in viral symmetry description	Fundamental misconceptions: treats mycoplasma as virus/fungus, describes bacterial capsule instead of endospore, draws strobilus as loose cone, confuses chloroplast with mitochondria, or reverses symmetry characteristics
Diagram / labelling	15%	7.5	Provides clear, well-proportioned diagram for part (c) showing sporangiophore with peltate head, sporangium, annulus of elaters, and central axis; labels all critical structures; may include supplementary sketches for viral symmetries or endospore layers that enhance clarity	Diagram present but disproportionate or missing key labels (e.g., elaters or sporangiophore structure); OR substitutes detailed description for diagram in part (c)	No diagram for part (c); OR diagram completely unrecognizable with no correct labels; OR draws unrelated structure (e.g., L.S. of stem instead of strobilus)
Examples & nomenclature	20%	10	Cites specific Indian plant diseases: sandal spike (Santalum album), little leaf of brinjal, or grassy shoot of sugarcane for phytoplasmas; names Bacillus subtilis or B. thuringiensis; specifies Equisetum arvense or E. ramosissimum; mentions Chlamydomonas, Spirogyra, or Ulothrix; identifies TMV, Cauliflower mosaic virus, or Adenovirus with correct taxonomic placement	Provides generic examples (e.g., 'some bacteria' or 'green algae') or mentions only one relevant example across all parts; some nomenclature errors	No specific examples; OR provides incorrect examples (e.g., Penicillium for mycoplasma, Escherichia coli for endospore-forming bacterium, Marchantia for Equisetum)
Process explanation	20%	10	Explains pathogenesis mechanism for mycoplasmas (phloem sieve tube colonization, effector secretion); describes endospore formation stages (asymmetric septation, engulfment, cortex synthesis, maturation, germination); clarifies strobilus development and spore dispersal via elaters; explains thylakoid membrane organization for light harvesting; articulates how viral symmetry determines packaging and host recognition	Lists structures without explaining their functional significance or developmental origin; mentions processes superficially without mechanistic detail	Purely static description with no process mentioned; OR invents non-existent processes; confuses sporulation with binary fission
Application / ecology	20%	10	Links mycoplasmas to agricultural losses in India and disease management challenges; connects endospore resistance to food preservation and sterilization protocols; relates Equisetum strobilus to evolutionary significance of spore-bearing structures; ties chloroplast structure to algal adaptation and biofuel potential; explains viral symmetry relevance to vaccine design and nanotechnology applications	Brief mention of practical relevance without elaboration; OR focuses only on one sub-part's applications while ignoring others	No application or ecological context provided; OR provides irrelevant applications (e.g., antibiotic production for mycoplasma, which lack cell wall targets)

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