Zoology 2023 Paper I 50 marks Discuss

Q4

(a) Draw a well-labelled diagram of adrenal gland and discuss the functions of its hormones. (20 marks) (b) Describe the general features and life cycle of Ascaris. (15 marks) (c) What are the skeletal elements of sponges? Describe the structure and types of various skeletal elements found in sponges. (15 marks)

हिंदी में प्रश्न पढ़ें

(a) अधिवृक्क ग्रंथि का एक सुचिहित चित्र बनाइए और इसके हार्मोनों के कार्यों का वर्णन कीजिए। (20 अंक) (b) ऐस्कैरिस के सामान्य लक्षणों और जीवन-चक्र का वर्णन कीजिए। (15 अंक) (c) स्पंज के कंकाल तत्व क्या हैं? स्पंज में पाए जाने वाले विभिन्न कंकाल तत्वों की संरचना एवं प्रकारों का वर्णन कीजिए। (15 अंक)

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Directive word: Discuss

This question asks you to discuss. 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 'discuss' demands a comprehensive, analytical treatment with balanced coverage across all three sub-parts. Allocate approximately 40% of time and words to part (a) given its 20 marks, and roughly 30% each to parts (b) and (c). Structure as: brief introduction → detailed diagram with hormonal functions for (a); morphological features and complete life cycle with epidemiological notes for (b); classification and structural details of spicules/spongin for (c); concluding with comparative evolutionary significance across the three phyla.

Key points expected

  • Part (a): Correctly labelled adrenal gland diagram showing cortex (zona glomerulosa, fasciculata, reticularis) and medulla; hormones (aldosterone, cortisol, androgens, adrenaline, noradrenaline) with specific target organs and physiological roles
  • Part (b): General features of Ascaris lumbricoides (morphology, habitat, parasitic adaptations); complete life cycle including infective stage, route of entry, tissue migration, pulmonary phase, intestinal maturation; epidemiology relevant to Indian context
  • Part (c): Definition and classification of skeletal elements in Porifera; detailed structure of calcareous and siliceous spicules (monoaxons, triaxons, tetraxons, polyaxons); spongin fibers; mention of Indian sponge fauna (e.g., Spongilla, Euspongia)
  • Comparative functional significance: mineralocorticoid vs. glucocorticoid action; neuroendocrine vs. steroid hormone pathways; structural support evolution from mesohyl to endoskeleton
  • Applied/clinical relevance: Addison's disease/Cushing's syndrome for adrenal; ascariasis burden and control in India; commercial value of bath sponges and spicule-based taxonomy

Evaluation rubric

DimensionWeightMax marksExcellentAveragePoor
Concept correctness25%12.5Accurately describes adrenal zonation and hormone biosynthesis pathway; correctly identifies Ascaris as dioecious with direct life cycle; precisely classifies spicule types by mineral composition and ray number without confusion between megascleres and microscleresBasic identification of adrenal parts and hormones with minor errors in cortical zones; general life cycle description missing pulmonary migration details; knows spicules are skeletal but confuses structural categoriesConfuses adrenal cortex with medulla hormones; describes Ascaris as hermaphroditic or with intermediate host; fundamental misunderstanding of sponge skeleton as extracellular vs. cellular
Diagram / labelling20%10Neat, proportionate adrenal diagram with 8+ accurate labels including blood supply; optional but clear Ascaris cross-section/life cycle schematic; sponge spicule types illustrated with proper ray orientationAdrenal diagram present but missing zona distinctions or venous drainage; Ascaris diagram generic; sponge skeletal elements described textually without visual representationNo diagram for adrenal despite explicit instruction; messy or mislabelled illustration; diagrams copied without integration with text
Examples & nomenclature15%7.5Uses standard nomenclature: cortisol (not hydrocortisone interchangeably), zona glomerulosa; Ascaris lumbricoides with authority; specific sponge genera (Euplectella, Hyalonema, Spongilla) with spicule types correctly namedCommon names mixed with scientific names; generic 'roundworm' for Ascaris; mentions sponges without genus-level examplesIncorrect scientific names, invented terminology, or confusion between Ascaris and Ancylostoma; no specific sponge examples
Process explanation25%12.5Clear hormonal action mechanisms (RAAS for aldosterone, fight-flight for catecholamines); stepwise life cycle with tissue migration timing; spicule formation via sclerocytes with silica/calcium deposition process explainedLists hormone functions without mechanism; chronological but incomplete life cycle; describes spicule structure without formation processRandom listing without process logic; misses critical life cycle stages; no understanding of how skeletal elements are secreted
Evolutionary / applied context15%7.5Links adrenal evolution to stress adaptation; notes Ascaris as model for parasitic nematode evolution and its relevance to lymphatic filariasis (Wuchereria) comparison; connects sponge spicules to early metazoan biomineralization and their use in paleontology/porcelain industryBrief mention of clinical importance for adrenal; notes ascariasis as public health problem; mentions commercial sponges without evolutionary significanceNo applied or evolutionary context; misses Indian public health relevance entirely; treats all three parts as isolated factual recall

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