All 8 questions from UPSC Civil Services Mains Zoology
2025 Paper II (400 marks total). Every stem reproduced in full,
with directive-word analysis, marks, word limits, and answer-approach pointers.
8Questions
400Total marks
2025Year
Paper IIPaper
Topics covered
Cell biology, genetics and evolution concepts (1)Cell membrane, mutations and inheritance patterns (1)Evolution theory, mimicry and molecular biology (1)Recombinant DNA technology, evolution and taxonomy (1)Embryology, biochemistry and neurophysiology (1)Cellular respiration, immunology and embryonic development (1)Respiratory physiology, immunology and developmental genetics (1)Embryology, biochemistry and reproductive physiology (1)
A
Q1
50M150wCompulsorywrite short notesCell biology, genetics and evolution concepts
Write on the following in about 150 words each : 10×5=50
(a) Protein sorting in Golgi apparatus (10 marks)
(b) Structure and function of Lampbrush chromosome (10 marks)
(c) Symptoms, causes and treatment of thalassemia (10 marks)
(d) Coupling and repulsion phases of linkage (10 marks)
(e) Sympatric and allopatric speciation (10 marks)
हिंदी में पढ़ें
निम्नलिखित प्रत्येक पर लगभग 150 शब्दों में लिखिए : 10×5=50
(a) गॉल्जी उपकरण में प्रोटीन छँटाई (10 अंक)
(b) लैम्पब्रश गुणसूत्र की संरचना एवं कार्य (10 अंक)
(c) थैलेसीमिया के लक्षण, कारण तथा उपचार (10 अंक)
(d) सहलग्नता की युग्मन एवं विकर्षण प्रावस्थाएँ (10 अंक)
(e) समस्थानिक एवं विस्थानिक जाति-उद्भवन (10 अंक)
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) explain: definition/context > points in order > small example > short close | (b) describe: define > structure or process in order > labelled diagram > significance | (c) analyse: intro > causes > effects > stakeholders/linkages > way forward | (d) explain: definition/context > points in order > small example > short close | (e) compare: paired headings or table > key differences > significance > conclusion Full marks: Precise terminology, labelled diagrams, and specific taxonomic examples for all parts.
50MexplainCell membrane, mutations and inheritance patterns
(a)(i) Describe composition of plasma membrane. (10 marks)
(a)(ii) Differentiate between facilitated and passive diffusion across the membrane with examples. (10 marks)
(b) Explain how mutations affect variations in population and natural selection. (15 marks)
(c) Draw pedigrees for autosomal recessive and sex-linked inheritance using examples from human. (15 marks)
हिंदी में पढ़ें
(a)(i) प्रद्रव्य झिल्ली की संरचना का वर्णन कीजिए । (10 अंक)
(a)(ii) प्रद्रव्य झिल्ली के आर-पार होने वाले सुकृत एवं निष्क्रिय विसरण के बीच सौदाहरण विभेदन कीजिए । (10 अंक)
(b) उत्परिवर्तन, जनसंख्या एवं प्राकृतिक चयन में विविधताओं को कैसे प्रभावित करता है, इसकी व्याख्या कीजिए । (15 अंक)
(c) मानव उदाहरणों का उपयोग करते हुए अप्रभावी अलिंगसूत्री एवं लिंग-सहलग्निक वंशागति के लिए वंशावलियों का रेखाचित्र बनायें । (15 अंक)
Answer approach & key points
Framework: Fluid Mosaic Model. (a(i)) describe: define > structure or process in order > labelled diagram > significance | (a(ii)) compare: paired headings or table > key differences > significance > conclusion | (b) explain: definition/context > points in order > small example > short close | (c) map: locate accurately > label > one line on why it matters Full marks: Precise terminology, labelled diagrams, and clear logical flow.
50MdescribeEvolution theory, mimicry and molecular biology
(a)(i) Describe the synthetic theory of evolution. (10 marks)
(a)(ii) Describe common types of mimicry in insects with suitable examples. (10 marks)
(b) Discuss the process of chain elongation during protein synthesis in prokaryotes. (15 marks)
(c) Describe the mechanism of ribozyme action and comment on its technological applications. (15 marks)
हिंदी में पढ़ें
(a)(i) विकास के संश्लिष्ट सिद्धांत का वर्णन कीजिए । (10 अंक)
(a)(ii) समुचित उदाहरणों के साथ कीटों में अनुहरण के सामान्य प्रकारों का वर्णन कीजिए । (10 अंक)
(b) प्राक्केंद्रकी कोशिकाओं में प्रोटीन संश्लेषण के दौरान श्रृंखला दीर्घीकरण की प्रक्रिया की विवेचना कीजिए । (15 अंक)
(c) राइबोजाइम क्रिया की क्रियाविधि का वर्णन कीजिए एवं इसके तकनीकी अनुप्रयोग पर टिप्पणी लिखिए । (15 अंक)
Answer approach & key points
Framework: UPSC Zoology Paper 2. (a(i)) describe: define > structure or process in order > labelled diagram > significance | (a(ii)) describe: define > structure or process in order > labelled diagram > significance | (b) discuss: intro > 3-4 dimensions > example > balanced close | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise definitions, named species/factors, clear mechanisms, and labelled diagrams.
50MdescribeRecombinant DNA technology, evolution and taxonomy
(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 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)
Answer approach & key points
Framework: UPSC Zoology Paper 2. (a) describe: define > structure or process in order > labelled diagram > significance | (b) discuss: intro > 3-4 dimensions > example > balanced close | (c) highlight: name the salient points > one line of substance each > close Full marks: Precise terminology, correct sequence, and specific examples (e.g., EcoRI, Eohippus).
Isolation of DNA and selection of vector
Digestion with restriction endonucleases
Ligation of insert into vector
Transformation and selection of clones
Reduction in number of toes (polydactyl to monodactyl)
Increase in body size and limb length
Modification of dentition (brachyodont to hypsodont)
50M150wCompulsorydescribeEmbryology, biochemistry and neurophysiology
Write on the following in about 150 words each : 10×5=50
(a) Block to polyspermy (10 marks)
(b) Fate map of frog embryo (10 marks)
(c) Activation energy based mechanism of enzyme action (10 marks)
(d) Structure of dipeptide unit of a protein (10 marks)
(e) Transmission of nerve impulse through synapse (10 marks)
हिंदी में पढ़ें
निम्नलिखित प्रत्येक पर लगभग 150 शब्दों में लिखिए : 10×5=50
(a) बहुशुक्राणुता का बाधित होना (10 अंक)
(b) मेंढक भ्रूण का नियति मानचित्र (10 अंक)
(c) एन्जाइम क्रिया की सक्रियण ऊर्जा आधारित क्रियाविधि (10 अंक)
(d) प्रोटीन के एक डाई-पेप्टाइड इकाई की संरचना (10 अंक)
(e) तंत्रिका आवेग का अंतर्प्रेरणी संचरण (10 अंक)
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) write short notes: define > 3-4 key features > one example > one-line significance | (b) write short notes: define > 3-4 key features > one example > one-line significance | (c) write short notes: define > 3-4 key features > one example > one-line significance | (d) write short notes: define > 3-4 key features > one example > one-line significance | (e) write short notes: define > 3-4 key features > one example > one-line significance Full marks: Precise mechanism, correct terminology, clear structure, and relevant examples.
Define polyspermy and its lethal consequence
Describe the fast block (membrane potential change)
50MdescribeCellular respiration, immunology and embryonic development
(a)(i) Write down the reactions that produce NADH during Krebs cycle. (10 marks)
(a)(ii) Explain the role of proton gradient in oxidative ATP synthesis. (10 marks)
(b) Describe characteristic features and specific functions of lymphocytes, monocytes and neutrophils. (15 marks)
(c) Diagrammatically describe the steps of development of heart in mammals. (15 marks)
हिंदी में पढ़ें
(a)(i) क्रेब चक्र के उन अभिक्रियाओं को लिखिए जो एन.ए.डी.एच. उत्पन्न करती हैं । (10 अंक)
(a)(ii) ऑक्सीकरणी ए.टी.पी. संश्लेषण में प्रोटान प्रवणता की भूमिका की व्याख्या कीजिए । (10 अंक)
(b) लसीकाणुओं (लिम्फोसाइड्स), एकलाणुओं (मोनोसाइड्स) एवं उदासीनरंजियों (न्यूट्रोफिल्स) के आभिलक्षणिक गुणों तथा विशिष्ट कार्यों का वर्णन कीजिए । (15 अंक)
(c) स्तनधारियों में हृदय परिवर्धन के चरणों का रेखाचित्रों द्वारा वर्णन कीजिए । (15 अंक)
Answer approach & key points
Framework: UPSC Zoology Paper 2. (a(i)) explain: definition/context > points in order > small example > short close | (a(ii)) explain: definition/context > points in order > small example > short close | (b) describe: define > structure or process in order > labelled diagram > significance | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise biochemical steps and anatomical stages with labelled diagrams.
Isocitrate to alpha-ketoglutarate (isocitrate dehydrogenase)
Alpha-ketoglutarate to succinyl-CoA (alpha-ketoglutarate dehydrogenase)
50MexplainRespiratory physiology, immunology and developmental genetics
(a)(i) Explain sigmoidal nature of oxygen dissociation curve for hemoglobin. (10 marks)
(a)(ii) Describe differences between adult and fetal hemoglobin and comment on their physiological significance. (10 marks)
(b) Discuss the mechanism of action of cytotoxic-T cell. (15 marks)
(c) What are homeotic genes ? Explain their role in body axis formation in chick. (15 marks)
हिंदी में पढ़ें
(a)(i) हीमोग्लोबिन के लिए आक्सीजन प्रथक्करण वक्र की सिग्मोइडल प्रकृति की व्याख्या कीजिए । (10 अंक)
(a)(ii) वयस्क एवं भ्रूण हीमोग्लोबिन के बीच अंतर का वर्णन कीजिए तथा इनके कार्यिकीय महत्व पर टिप्पणी लिखिए । (10 अंक)
(b) कोशिकाविषी-ट कोशिका की कार्यविधि का वर्णन कीजिए । (15 अंक)
(c) समापवर्धी जीन क्या हैं ? चुजे में पिंडाक्ष बनने में उनकी भूमिका की व्याख्या कीजिए । (15 अंक)
Answer approach & key points
Framework: null. (a(i)) explain: definition/context > points in order > small example > short close | (a(ii)) describe: define > structure or process in order > labelled diagram > significance | (b) discuss: intro > 3-4 dimensions > example > balanced close | (c) explain: definition/context > points in order > small example > short close Full marks: Precise mechanisms, labelled diagrams, specific gene names, and clear physiological links.
T-state (tense) vs R-state (relaxed) conformational change
Cooperative binding of O2 to heme groups
Bohr effect: pH and CO2 influence affinity
Labelled diagram of sigmoidal curve
Subunit composition: HbA (α2β2) vs HbF (α2γ2)
Higher O2 affinity of HbF (left-shifted curve)
Physiological significance: O2 transfer from mother to fetus
50MdescribeEmbryology, biochemistry and reproductive physiology
(a) Describe the stages of fertilization in chick with diagram. (20 marks)
(b) Draw structure of cholesterol and explain its role in health and diseases. (15 marks)
(c) Discuss the role of ovarian hormones in female reproduction. (15 marks)
हिंदी में पढ़ें
(a) चुजे में निषेचन के चरणों का चित्रों के साथ वर्णन कीजिए । (20 अंक)
(b) कोलेस्ट्रॉल की संरचना बनायें एवं स्वास्थ्य तथा बीमारियों में इसकी भूमिका की व्याख्या कीजिए । (15 अंक)
(c) मादा प्रजनन में अंडाशयी हार्मोनों की भूमिका की विवेचना कीजिए । (15 अंक)
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) describe: define > structure or process in order > labelled diagram > significance | (b) explain: definition/context > points in order > small example > short close | (c) discuss: intro > 3-4 dimensions > example > balanced close Full marks: Precise anatomical/chemical details, labelled diagrams, clear mechanistic links, and specific taxon references.