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Zoology

UPSC Zoology 2024 — Paper II

All 8 questions from UPSC Civil Services Mains Zoology 2024 Paper II (400 marks total). Every stem reproduced in full, with directive-word analysis, marks, word limits, and answer-approach pointers.

8Questions
400Total marks
2024Year
Paper IIPaper

Topics covered

Cell biology and genetics (1)Cell organelles and chromatin structure (1)Genetics and molecular biology (1)Evolution and systematics (1)Immunology, physiology and embryology (1)Physiology and endocrinology (1)Reproduction, biochemistry and muscle physiology (1)Digestion, metabolism and organogenesis (1)

A

Q1
50M 150w Compulsory write short notes Cell biology and genetics

Write on the following in about 150 words each: (a) Polytene chromosome (10 marks) (b) Difference between male heterogamety and female heterogamety with examples (10 marks) (c) Types of chromosomal aberrations (10 marks) (d) Geographic versus reproductive isolation (10 marks) (e) Main types of molecular mutations and their effect on phenotype (10 marks)

हिंदी में पढ़ें

निम्नलिखित प्रत्येक पर लगभग 150 शब्दों में लिखिए : (a) बहुपट्टी गुणसूत्र (10 अंक) (b) उदाहरण सहित नर विषमयुग्मनी (हेट्रोगैमिटी) एवं मादा विषमयुग्मनी के बीच अंतर (10 अंक) (c) गुणसूत्री विपथन के प्रकार (10 अंक) (d) भौगोलिक बनाम प्रजननात्मक पृथक्करण (10 अंक) (e) आणविक उत्परिवर्तन के मुख्य प्रकार तथा लक्षणप्ररूप (फीनोटाइप) पर उनका प्रभाव (10 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) compare: paired headings or table > key differences > significance > conclusion | (c) enumerate: list the items in order > one line each > no commentary | (d) compare: paired headings or table > key differences > significance > conclusion | (e) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise definitions, correct mechanisms, specific named taxa/species, clear distinctions, and accurate examples for all parts.

  • Define polytene chromosome (giant chromosome)
  • Explain endoreduplication mechanism (mitosis without cytokinesis)
  • Describe banding pattern (light/dark bands)
  • Name example taxon (Diptera, e.g., Drosophila)
  • Define male heterogamety (XY system)
  • Define female heterogamety (ZW system)
  • Give example for male (Mammals, Drosophila)
  • Give example for female (Birds, Lepidoptera)
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Q2
50M discuss Cell organelles and chromatin structure

(a) Give an account of ultrastructure of rough and smooth endoplasmic reticulum. Also discuss the role of endoplasmic reticulum in cell secretion. (20 marks) (b) Distinguish between heterochromatin and euchromatin in their structure and function with examples. (15 marks) (c) What are signal molecules? How do defects in signalling pathway cause pathological changes? (15 marks)

हिंदी में पढ़ें

(a) खुरदरी तथा चिकनी अंतर्द्रव्यी जालिका की सूक्ष्म संरचना का विवरण दीजिए। कोशिकीय स्रवण में अंतर्द्रव्यी जालिका की भूमिका की भी चर्चा कीजिए। (20 अंक) (b) विषमक्रोमैटिन (हेट्रोक्रोमैटिन) तथा युक्रोमैटिन की संरचना तथा कार्यों में उदाहरण सहित अंतर स्पष्ट कीजिए। (15 अंक) (c) संकेत अणु (सिग्नल मॉलिक्यूल) क्या हैं? संकेत मार्ग में दोष किस प्रकार रोगात्मक (पैथोलॉजिकल) परिवर्तन उत्पन्न करते हैं? (15 अंक)

Answer approach & key points

(a) discuss: intro > 3-4 dimensions > example > balanced close | (b) compare: paired headings or table > key differences > significance > conclusion | (c) explain: definition/context > points in order > small example > short close Full marks: Comprehensive, accurate, with specific examples and clear mechanisms.

  • RER: ribosomes, cisternae, rough appearance
  • SER: smooth, tubular, no ribosomes
  • Secretion: protein synthesis, folding, transport
  • Link to Golgi apparatus and vesicles
  • Heterochromatin: condensed, transcriptionally inactive
  • Euchromatin: decondensed, transcriptionally active
  • Structural differences (staining, packing)
  • Functional differences (gene expression)
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Q3
50M describe Genetics and molecular biology

(a) What is sex-determination? Give an account of genic balance theory of sex-determination in Drosophila with examples from abnormal karyotypes. (20 marks) (b) What is DNA replication? Describe the process of DNA replication in prokaryotes. (15 marks) (c) Discuss gene regulation mechanisms in E. coli. (15 marks)

हिंदी में पढ़ें

(a) लिंग-निर्धारण क्या है? ड्रोसोफिला में लिंग-निर्धारण के जीनी संतुलन (जीनिक बैलेंस) सिद्धांत का विवरण असामान्य गुणसूत्रप्ररूपों (कैरियोटाइप) के उदाहरणों सहित दीजिए। (20 अंक) (b) डी० एन० ए० प्रतिकृतियन क्या है? प्राक्केंद्रकी में डी० एन० ए० प्रतिकृतियन की प्रक्रिया का वर्णन कीजिए। (15 अंक) (c) ई० कोलाई में जीन नियमन (जीन रेगुलेशन) तंत्र की चर्चा कीजिए। (15 अंक)

Answer approach & key points

Framework: Zoology, Paper 2. (a) account for: state the phenomenon > the causes in order of weight > conclusion | (b) describe: define > structure or process in order > labelled diagram > significance | (c) discuss: intro > 3-4 dimensions > example > balanced close Full marks: Comprehensive, accurate, and well-structured answers with clear diagrams and examples.

  • Define sex-determination as the mechanism of sex development
  • State the X:A ratio (X chromosome to Autosome ratio)
  • Explain the mechanism of genic balance theory
  • Provide examples of abnormal karyotypes (e.g., XXY, XO, XXX)
  • Define DNA replication as the synthesis of DNA
  • Identify the origin of replication (oriC)
  • Describe the semi-conservative nature of replication
  • Explain the roles of key enzymes (helicase, primase, DNA pol III)
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Q4
50M describe Evolution and systematics

(a) Describe the stages of human evolution and mention the major hominid forms giving their time of origin. (20 marks) (b) What is Hardy-Weinberg law? How is gene frequency changed by mutation and genetic drift in populations? (15 marks) (c) What is the difference between systematics and taxonomy? Differentiate between classical and molecular taxonomy with the tools used. (15 marks)

हिंदी में पढ़ें

(a) मानव उद्विकास के चरणों का वर्णन कीजिए तथा मुख्य होमिनिड अवस्थाओं (फॉर्म) को उनकी उत्पत्ति के काल को दर्शाते हुए उल्लिखित कीजिए। (20 अंक) (b) हार्डी-वीनबर्ग नियम क्या है? समष्टि में उत्परिवर्तन तथा आनुवंशिक विचलन (जेनेटिक ड्रिफ्ट) से जीन आवृत्ति कैसे परिवर्तित होती है? (15 अंक) (c) वर्गीकरण-विज्ञान तथा वर्गिकी में क्या अंतर है? चिरप्रतिष्ठित एवं आणविक वर्गिकी में प्रयुक्त उपकरणों सहित अंतर कीजिए। (15 अंक)

Answer approach & key points

Framework: null. (a) describe: define > structure or process in order > labelled diagram > significance | (b) explain: definition/context > points in order > small example > short close | (c) compare: paired headings or table > key differences > significance > conclusion Full marks: Comprehensive, chronologically accurate, with precise terminology and clear differentiation of concepts.

  • Define human evolution and its stages
  • List major hominid forms in chronological order
  • Provide time of origin for each form
  • Describe key morphological/behavioral changes
  • State Hardy-Weinberg equilibrium conditions
  • Define gene frequency change mechanism
  • Explain mutation's role in introducing variation
  • Explain genetic drift's random sampling effect
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B

Q5
50M 150w Compulsory describe Immunology, physiology and embryology

Write on the following in about 150 words each: (a) Functions of immunoglobulins (10 marks) (b) ABO system of blood groups and its basis, and erythroblastosis foetalis (8+2=10 marks) (c) Olfactory pathways and physiology of olfaction (10 marks) (d) (i) Gastrulation in frog (5 marks) (ii) Biogenetic law (5 marks) (e) (i) Stem cells (5 marks) (ii) Types of placenta among mammals (5 marks)

हिंदी में पढ़ें

निम्नलिखित प्रत्येक पर लगभग 150 शब्दों में लिखिए : (a) प्रतिरक्षाल्बुलिन (इम्युनोग्लोब्युलिन) के कार्य (10 अंक) (b) श्वेतर समूहों की ABO प्रणाली व इसके आधार, एवं इरिथ्रोब्लास्टोसिस फोटेलिस (8+2=10 अंक) (c) घ्राण मार्ग व घ्राण की कार्यिकी (10 अंक) (d) (i) मेंढक में कंडुकन (5 अंक) (ii) जाति-आवर्तन नियम (5 अंक) (e) (i) मूल कोशिका (5 अंक) (ii) स्तनियों में अपरा के प्रकार (5 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(i)) write short notes: define > 3-4 key features > one example > one-line significance | (d(ii)) write short notes: define > 3-4 key features > one example > one-line significance | (e(i)) write short notes: define > 3-4 key features > one example > one-line significance | (e(ii)) write short notes: define > 3-4 key features > one example > one-line significance Full marks: Precise definitions, clear mechanisms, labelled diagrams, and specific examples.

  • Neutralization of toxins and pathogens
  • Opsonization and phagocytosis
  • Activation of complement system
  • Agglutination of antigens
  • Antigen-antibody basis of ABO groups
  • Inheritance of blood groups
  • Mechanism of Rh incompatibility
  • Consequences for the fetus
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Q6
50M explain Physiology and endocrinology

(a) Explain the structure of nephron and its role in urine formation. Add a note on hormonal regulation of urine formation. (15+5=20 marks) (b) Classify hormones and write down the process of steroid hormone biosynthesis. (15 marks) (c) What do you mean by teratogenesis? Explain the genetic and induced teratogenesis. (5+10=15 marks)

हिंदी में पढ़ें

(a) वृक्काणु (नेफ्रॉन) की संरचना एवं मूत्र-निर्माण में इसकी भूमिका की व्याख्या कीजिए। मूत्र-निर्माण के हार्मोनी नियमन पर एक टिप्पणी लिखिए। (15+5=20 अंक) (b) हार्मोनों का वर्गीकरण कीजिए तथा स्टेरॉयड हार्मोन के जैव संश्लेषण की प्रक्रिया को लिखिए। (15 अंक) (c) विकृजनन से आप क्या समझते हैं? आनुवंशिक एवं प्रेरित विकृजनन की व्याख्या कीजिए। (5+10=15 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) explain: definition/context > points in order > small example > short close Full marks: Precise mechanisms, labelled diagrams, named examples, and clear distinctions.

  • Labelled diagram of nephron (Bowman's capsule, tubules)
  • Mechanism of filtration, reabsorption, and secretion
  • Role of ADH and Aldosterone in regulation
  • Link between structure and specific function
  • Classification by chemical nature (peptide, steroid, amine)
  • Stepwise process of steroid biosynthesis
  • Mention of cholesterol as precursor
  • Identification of key enzymes (e.g., CYP11A1)
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Q7
50M describe Reproduction, biochemistry and muscle physiology

(a) Describe the process of spermatogenesis. Add a note on the role of Golgi bodies in the formation of acrosome. (15+5=20 marks) (b) Why are vitamins also called coenzymes? Justify. (15 marks) (c) Explain the mechanism of contraction in skeletal muscle. What do you mean by Rheobase and Chronaxie? (12+3=15 marks)

हिंदी में पढ़ें

(a) शुक्राणुजनन की प्रक्रिया का वर्णन कीजिए। अग्रपिंडक के निर्माण में गॉल्जी काय की भूमिका पर एक टिप्पणी लिखिए। (15+5=20 अंक) (b) विटामिनों को सह-एंजाइम भी क्यों कहा जाता है? सिद्ध कीजिए। (15 अंक) (c) कंकाल पेशी में संकुचन की क्रियाविधि की व्याख्या कीजिए। अलिबंधारा (रियोबेस) व कालमान (क्रोनेक्सी) से आप क्या समझते हैं? (12+3=15 अंक)

Answer approach & key points

Framework: Spermatogenesis, Coenzyme theory, Sliding Filament theory. (a) describe: define > structure or process in order > labelled diagram > significance | (b) justify: definition/context > points in order > small example > short close | (c) explain: definition/context > points in order > small example > short close Full marks: Precise mechanisms, correct definitions, and labelled diagrams

  • Spermatogenesis stages
  • Golgi-acrosome link
  • Vitamin as coenzyme precursor
  • Sliding filament theory
  • Rheobase definition
  • Chronaxie definition
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Q8
50M discuss Digestion, metabolism and organogenesis

(a) Write about the role of liver and pancreas in digestion. Add a note on neural and hormonal regulation of their secretions. (15+5=20 marks) (b) Discuss the role of oxidative phosphorylation in cellular and tissue metabolism. (15 marks) (c) Describe the organogenesis of eye. (15 marks)

हिंदी में पढ़ें

(a) पाचन में यकृत एवं अग्न्याशय की भूमिका के बारे में लिखिए। इनके स्रवण के तंत्रिकीय एवं हार्मोनी नियमन पर एक टिप्पणी लिखिए। (15+5=20 अंक) (b) कोशिकीय एवं उत्तक उपापचय में ऑक्सीकरणी (ऑक्सीडेटिव) फॉस्फोरिलेशन की भूमिका का वर्णन कीजिए। (15 अंक) (c) नेत्र के अंगविकास का वर्णन कीजिए। (15 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) discuss: intro > 3-4 dimensions > example > balanced close | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise mechanisms, labelled diagrams, and clear linkage of structure to function.

  • Liver: bile synthesis, storage, and role in lipid digestion
  • Pancreas: exocrine enzymes (amylase, lipase, trypsin) and bicarbonate secretion
  • Neural regulation: vagal stimulation of pancreatic secretion
  • Hormonal regulation: CCK and secretin roles in pancreatic/bile secretion
  • Definition of oxidative phosphorylation and its location (mitochondria)
  • Electron transport chain (ETC) complexes and proton gradient generation
  • Chemiosmotic coupling and ATP synthase mechanism
  • Link to cellular energy (ATP) production for tissue function
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