Zoology 2021 Paper I 50 marks Explain

Q6

(a) Define correlation. Explain its types and methods of computing coefficient of correlation. (20 marks) (b) Write a note on ecological pyramids with suitable examples. (15 marks) (c) What are pheromones? Discuss their role in insects. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) सहसंबंध को परिभाषित कीजिए। सहसंबंध के प्रकार और इसके गुणांक की गणना के तरीकों की व्याख्या कीजिए। (20 अंक) (b) पारिस्थितिक पिरामिडों पर उपयुक्त उदाहरणों सहित एक टिप्पणी लिखिए। (15 अंक) (c) फेरोमोन क्या हैं? कीटों में उनकी भूमिका की चर्चा कीजिए। (15 अंक)

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Directive word: Explain

This question asks you to explain. 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 'explain' demands clear exposition of concepts with logical reasoning. Allocate approximately 40% of time/words to part (a) given its 20 marks, 30% each to parts (b) and (c). Structure: brief introduction defining correlation → detailed body covering types (positive/negative, linear/non-linear), Pearson and Spearman methods with formulae → ecological pyramids (number, biomass, energy) with Indian ecosystem examples → pheromone types and insect applications → concise conclusion linking statistical tools to ecological research.

Key points expected

  • Part (a): Definition of correlation as statistical relationship between two variables; distinction between positive, negative, and zero correlation; linear vs non-linear types
  • Part (a): Pearson's product-moment correlation coefficient (r) formula and computation steps; Spearman's rank correlation (ρ) for non-parametric data with worked illustration
  • Part (b): Ecological pyramid concept and Lindeman's trophic-dynamic theory; three types (pyramid of number, biomass, energy) with specific Indian examples (e.g., grassland ecosystem of Terai, pond ecosystem)
  • Part (b): Explanation of inverted pyramids (biomass in aquatic ecosystems, number in parasitic food chains) with reasoning
  • Part (c): Pheromone definition as semiochemicals; classification into sex pheromones, aggregation pheromones, alarm pheromones, trail pheromones
  • Part (c): Specific insect examples: Bombyx mori (bombykol), Apis mellifera (queen substance), Tribolium (aggregation), Lasius niger (trail marking); applied context in IPM and pest control

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness22%11Precise definitions: correlation as covariation not causation; accurate formulae for Pearson's r and Spearman's ρ; correct pyramid terminology (Lindeman, trophic levels); accurate pheromone classification by function and chemistryBasic definitions correct but formulae partially wrong or incomplete; pyramid types named without clear distinction; pheromones defined but types confusedFundamental errors: correlation equated with causation; wrong formulae; pyramids confused with food webs; pheromones mixed with hormones or allomones
Diagram / labelling18%9Three clear diagrams: scatter plots showing positive/negative/no correlation with trend lines; all three pyramid types (upright and inverted) with proper trophic levels labelled; pheromone communication pathway diagram with sender-receiver interactionTwo diagrams present but poorly labelled or one type missing; pyramids drawn without units or scale indication; no diagram for pheromone mechanismNo diagrams or incomprehensible sketches; missing axes labels, no indication of energy flow direction; diagrams contradict text
Examples & nomenclature20%10Indian ecosystem examples: Sundarbans mangrove (inverted biomass pyramid), Terai grassland (upright number pyramid); specific pheromones named (bombykol, disparlure, queen mandibular pheromone) with source species; statistical examples with realistic data setsGeneric examples without specificity; 'forest ecosystem' without naming; pheromones listed without chemical names or species; no Indian examplesNo examples or factually wrong examples; invented pheromone names; ecosystems confused (marine vs terrestrial pyramid shapes)
Process explanation22%11Step-wise computation of r: mean calculation, deviation scores, cross-products, summation, final division; clear explanation of why pyramids differ (biomass turnover rate, energy transfer efficiency ~10%); pheromone reception mechanism (antennal receptors, signal transduction, behavioral response cascade)Formula stated but computation steps skipped; pyramids described without explaining energy loss mechanism; pheromone action described as 'smell attracts' without receptor-level detailNo process explanation; mere listing of terms; confused causal chains; computational steps completely wrong
Evolutionary / applied context18%9Evolutionary significance: honest signaling in pheromones, kin selection in alarm signals; applied value: correlation in wildlife census analysis, pheromone traps in Indian agriculture (pink bollworm Pectinophora gossypiella management), ecological pyramids in sustainable yield determination for fisheries (CFRI models)Brief mention of pest control without specificity; no evolutionary context; generic statement about 'useful in research'No applied or evolutionary context; irrelevant digression into genetic engineering; confusion with biopesticides

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