Q4
(a) Diagrammatically present the Geological Time Scale up to 'Epoch'. Write a note on the different types of fossils found in nature. (20 marks) (b) Describe the symptoms, causal organism, disease cycle and control measures of red rot of sugarcane. (15 marks) (c) What is stele? Give an illustrated account of various types of steles observed in pteridophytes. (15 marks)
हिंदी में प्रश्न पढ़ें
(a) अरेख द्वारा भूवैज्ञानिक समय पैमाने को 'युग' (ईपॉक) तक प्रस्तुत कीजिए। प्रकृति में पाए जाने वाले विभिन्न जीवाश्मों पर एक टिप्पणी लिखिए। (20 अंक) (b) गन्ने में रेड रॉट के लक्षण, कारक जीव, बीमारी चक्र और नियंत्रण के उपायों का वर्णन कीजिए। (15 अंक) (c) रंभ क्या है? टेरिडोफाइट में पाए जाने वाले विभिन्न प्रकार के रंभों का एक सचित्र विवरण प्रस्तुत कीजिए। (15 अंक)
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 coverage of all three sub-parts with appropriate illustrations. Allocate approximately 40% of time/words to part (a) given its 20 marks, and roughly 30% each to parts (b) and (c). Structure as: (a) tabular/chronological presentation of GTS with fossil note, (b) disease description with cycle diagram, (c) stele definition with comparative diagrams—no formal conclusion needed but ensure all sub-parts are visibly demarcated.
Key points expected
- Part (a): Hierarchical presentation of Geological Time Scale from Eon to Epoch with correct durations (Precambrian 4600-541 MYA, Phanerozoic subdivisions), accompanied by classification of fossils into body fossils, trace fossils, chemical fossils and microfossils with specific Indian examples
- Part (a): Mention of index fossils and their stratigraphic significance, with reference to Gondwana flora/fossils from Indian geological formations
- Part (b): Accurate identification of Colletotrichum falcatum (Glomerella tucumanensis) as causal organism with perfect and imperfect stages
- Part (b): Detailed symptomatology including reddening of internodes, white spots with brown margins, top rot, whip-like appearance; disease cycle showing primary and secondary infection through setts, soil, and conidia; integrated management including resistant varieties (Co 1148, Co 527), hot water treatment, crop rotation, and fungicidal control
- Part (c): Definition of stele as central vascular cylinder with pericycle; illustrated account of protostele (haplo-, actino-, plectostele), siphonostele (ectophloic, amphiphloic, solenostele, dictyostele), and atactostele with pteridophyte examples (Lycopodium, Selaginella, Pteridium, Adiantum)
- Part (c): Evolutionary trend in stellar organization from protostele to dictyostele with reference to stellar theory of Jeffrey and Zimmermann
Evaluation rubric
| Dimension | Weight | Max marks | Excellent | Average | Poor |
|---|---|---|---|---|---|
| Concept correctness | 22% | 11 | For (a): Precise GTS chronology with correct boundaries and no anachronisms; accurate fossil classification with clear distinctions. For (b): Correct pathogen nomenclature, accurate symptom sequence, scientifically sound disease cycle. For (c): Accurate stellar terminology, correct anatomical relationships between xylem, phloem, and pith | Broadly correct GTS with minor boundary errors; basic fossil types named; pathogen identified with minor errors in disease cycle; stele defined with some confusion between stellar types | Serious chronological errors in GTS; confused fossil classification; wrong pathogen or symptom description; fundamental misunderstanding of stellar anatomy |
| Diagram / labelling | 24% | 12 | For (a): Clear hierarchical diagram/table of GTS with Epoch-level detail. For (b): Disease cycle diagram showing conidial germination, appressoria formation, and host penetration. For (c): Minimum 3 stellar diagrams (protostele, siphonostele, dictyostele) with accurate cellular detail, proper shading, and complete labelling of xylem, phloem, pith, pericycle, and leaf gaps | Basic GTS table without visual hierarchy; simple disease cycle sketch; 2 stellar diagrams with incomplete labelling | Absent or irrelevant diagrams; poorly drawn cycles; single confused stellar diagram or diagrams without labels |
| Examples & nomenclature | 18% | 9 | For (a): Indian Gondwana fossils (Glossopteris, Gangamopteris) and Siwalik vertebrates; index fossils like Paradoxides, Graptolites. For (b): Resistant varieties (Co 1148, Co 527, Co 6806), hot water treatment specifics (52°C/30 min). For (c): Genus-specific examples—Lycopodium clavatum (protostele), Pteridium (dictyostele), Adiantum (solenostele) | Some Indian fossil examples; generic resistant variety mention; 2-3 pteridophyte examples with partial accuracy | No Indian examples; no variety names; no specific pteridophyte genera cited |
| Process explanation | 20% | 10 | For (a): Mechanism of fossil formation (petrification, carbonization, moulds/casts) with preservation conditions. For (b): Stepwise disease cycle—overwintering in setts, conidia production, dispersal, penetration, colonization, symptom development, secondary spread. For (c): Evolutionary progression from solid protostele to dissected dictyostele with functional significance of leaf gaps | Basic fossil formation described; linear disease progression without overwintering detail; stellar types listed without evolutionary connection | No process explanation for fossils; confused or absent disease cycle; no understanding of stellar evolution |
| Application / ecology | 16% | 8 | For (a): Stratigraphic correlation using fossils; biostratigraphy and paleoclimatic inferences from Gondwana flora. For (b): Integrated disease management—cultural (3-year rotation with paddy), chemical (carbendazim, copper fungicides), biological (Trichoderma), and host resistance deployment. For (c): Ecological significance of stellar modifications in relation to habitat adaptation and water conduction efficiency | Basic mention of fossil dating; chemical control listed; minimal ecological context for stellar types | No applied aspects; no control measures; no ecological significance discussed |
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