Zoology 2025 Paper II 50 marks Describe

Q4

(a) Describe the steps of constructing a recombinant DNA and its cloning. (20 marks) (b) Discuss the major morphological modifications during horse evolution. (15 marks) (c) Write down the salient features of zoological nomenclature. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) पुनर्योजज डी.एन.ए. का निर्माण एवं इसके क्लोनिंग के चरणों का वर्णन कीजिए । (20 अंक) (b) घोड़े के विकासक्रम के दौरान प्रमुख आकृतिक परिवर्तनों की विवेचना कीजिए । (15 अंक) (c) प्राणी नामपद्धति की प्रमुख विशिष्टताओं को लिखिए । (15 अंक)

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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 systematic, detailed exposition of processes and features. Allocate approximately 40% of time/words to part (a) on rDNA construction and cloning (20 marks), 30% each to part (b) on horse evolution (15 marks) and part (c) on nomenclature (15 marks). Structure: brief introduction linking biotechnology, evolution and taxonomy as pillars of modern zoology; body with three clearly demarcated sections; conclusion emphasizing how these domains interconnect in contemporary biological research.

Key points expected

  • Part (a): Isolation of target DNA and vector DNA; restriction enzyme digestion; ligation using DNA ligase; transformation into host cells; selection and screening of recombinant clones
  • Part (a): Detailed description of cloning vectors (plasmids, cosmids, BACs, YACs) and host systems (E. coli, yeast); mention of antibiotic resistance and blue-white screening
  • Part (b): Sequential morphological changes from Eohippus to Equus: reduction of toes (polydactyly to monodactyly), elongation of limbs, hypsodonty in dentition, enamel complexity, cranial and facial elongation
  • Part (b): Environmental drivers of horse evolution: forest to grassland transition, cursorial adaptation for speed, grazing diet specialization; mention of fossil evidence from North America and India (Siwalik deposits)
  • Part (c): Binomial nomenclature principles; priority rule, type concept, synonymy; role of ICZN; mandatory Latinization; authorship and date citation; rules for naming new species and higher taxa

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness22%11Accurately defines all technical terms (restriction enzymes, ligase, transformation, hypsodonty, cursorial adaptation, holotype, lectotype); correctly identifies enzyme classes (Type II endonucleases); precise on nomenclatural rules (Principle of Priority, Principle of Homonymy)Generally correct definitions with minor errors (confusing transformation with transfection; vague on dental terminology; incomplete understanding of type specimens)Major conceptual errors (calling restriction enzymes 'DNA scissors' without function; confusing Eohippus with modern horse ancestor; stating genus-species order can be reversed)
Diagram / labelling18%9Clear, self-drawn diagrams: (a) rDNA construction showing vector, insert, RE sites, ligated product; (b) horse limb evolution series (Eohippus-Mesohippus-Merychippus-Pliohippus-Equus) with labeled skeletal changes; (c) hierarchical classification diagram showing type specimen designationBasic diagrams present but incomplete labeling, missing scale, or borrowed from memory without adaptation; horse evolution shown as linear ladder rather than branching patternNo diagrams or irrelevant sketches; diagrams without any labeling; copied textbook figures without understanding
Examples & nomenclature20%10Specific examples: pBR322/pUC19 for vectors; HindIII, EcoRI as RE examples with palindromic recognition sites; Indian fossil sites (Jammu Siwaliks, Kutch for Equus); cites actual published species names with author and date (e.g., Equus caballus Linnaeus, 1758)Generic examples (plasmid, restriction enzyme) without specificity; mentions Siwaliks but no specific formation; binomial names without authors or datesNo specific examples; invented species names; incorrect author citations; confuses common names with scientific names
Process explanation22%11Logical stepwise progression for rDNA: isolation → digestion → ligation → transformation → selection → amplification; for horse evolution: stratigraphic sequence with dating; for nomenclature: publication → registration → validation pathway; explains 'why' at each stepSteps listed but causal connections weak; chronological order maintained but mechanisms unclear; screening methods mentioned without explaining principleRandom order of steps; missing critical steps (no mention of competent cells or antibiotic selection); no temporal framework for evolution; no process for nomenclature validation
Evolutionary / applied context18%9Connects rDNA to biotechnology applications (insulin production, gene therapy, transgenic crops); explains horse evolution as classic example of adaptive radiation and orthogenesis debate; links nomenclature to biodiversity documentation, conservation, and bioprospecting in India; mentions ethical and biosafety considerationsBrief mention of applications without elaboration; horse evolution as isolated example; nomenclature as purely academic exerciseNo applied context; no mention of modern relevance; fails to connect the three sub-parts thematically

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