All 8 questions from UPSC Civil Services Mains Zoology 2021 Paper II (400 marks total). Every stem reproduced in full, with directive-word analysis, marks, word limits, and answer-approach pointers.
8Questions
400Total marks
2021Year
Paper IIPaper
Topics covered
Molecular biology, genetics, evolution and taxonomy (1)Cell biology, cell cycle and membrane structure (1)Genetics, chromosome mutations and Mendelian inheritance (1)Evolution, speciation and origin of life (1)Biochemistry, physiology and reproductive biology (1)Endocrinology, signal transduction and bioenergetics (1)Physiology of digestion, respiration and sensory system (1)Developmental biology, cell communication and gametogenesis (1)
A
Q1
50M150wCompulsorydescribeMolecular biology, genetics, evolution and taxonomy
Write your answer in about 150 words for each of the following : 10×5=50
(a) Describe the requirement of proteins for the initiation of transcription in an eukaryote. 10
(b) What is modern concept of gene ? Describe the test of allilism with suitable example. 10
(c) Define mimicry. Discuss the types of mimicry with suitable examples. 10
(d) Describe the use of molecular techniques in animal taxonomy. 10
(e) What is cladistics ? Discuss the international code of biological nomenclature. 10
हिंदी में पढ़ें
निम्नलिखित प्रत्येक के लिये लगभग 150 शब्दों में अपना उत्तर लिखिये : 10×5=50
(a) एक सुकेंद्रकी (यूकेरियाट) में अनुलेखन की शुरुआत करने में प्रोटीन की आवश्यकता का वर्णन कीजिए । 10
(b) जीन की आधुनिक अवधारणा क्या है ? विकल्पता (एलिलिज्म) के परीक्षण का वर्णन उपयुक्त उदाहरण सहित कीजिए । 10
(c) अनुहरण (मिमिक्री) को परिभाषित कीजिए । उपयुक्त उदाहरणों के साथ मिमिक्री के प्रकारों का वर्णन कीजिए । 10
(d) जन्तु वर्गिकी में आणविक तकनीकों के उपयोग का वर्णन कीजिए । 10
(e) वंशशाखिकी (क्लैडिस्टिक्स) क्या है ? जैविक नामपद्धति के अन्तर्राष्ट्रीय कोड का वर्णन कीजिए । 10
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) describe: define > structure or process in order > labelled diagram > significance | (c) define: precise definition > the distinguishing feature > one example | (d) describe: define > structure or process in order > labelled diagram > significance | (e) discuss: intro > 3-4 dimensions > example > balanced close Full marks: Precise mechanisms, named species, and clear logical flow for all parts.
RNA polymerase II and general transcription factors (TFIID, TFIIA, TFIIB, TFIIF, TFIIE, TFIIH)
TBP binding to TATA box and pre-initiation complex
TFIIH helicase and CTD phosphorylation
Modern gene concept: split genes, overlapping genes, non-coding RNA genes
Test of allelism by complementation
Benzer rII example or another example
Definition of mimicry with model and mimic
Batesian and Müllerian mimicry with examples
Aggressive mimicry with an example
DNA barcoding with COI
Sequencing of other genes for phylogeny
PCR-based markers such as RFLP, RAPD and microsatellites
Cladistics as classification by shared derived characters and monophyly
Cladogram
ICZN rules: binomial name, priority from 1758, type specimens
50MdiscussCell biology, cell cycle and membrane structure
(a) What is cell cycle ? Draw an overview of molecular events during cell cycle. Discuss the role of protein kinases in the regulation of meiotic cell cycle. 20
(b) Lysosomes are polymorphic, justify. Draw a diagram representing the dynamic aspect of lysosome system. Write down the functions of lysosomes. 15
(c) Glycoproteins are asymmetrically distributed in a plasma membrane, explain. Give an overview of membrane function. 15
हिंदी में पढ़ें
(a) कोशिका चक्र क्या है ? कोशिका चक्र के दौरान आणविक घटनाओं का सिंहावलोकन कीजिए । अर्धसूत्री कोशिका चक्र के नियमन में प्रोटीन काइनेजेस की भूमिका का वर्णन कीजिए । 20
(b) लयनकाय (लाइसोसोम्स) बहुरूपी होते हैं, सिद्ध कीजिए । लाइसोसोम प्रणाली के गतिशील पहलू को दर्शाते हुए आरेखित कीजिए । लाइसोसोम्स के कार्यों को कलमबद्ध कीजिए । 15
(c) प्रद्रव्य (प्लाज्मा) झिल्ली में ग्लाइकोप्रोटीन असममित रूप से वितरित होते हैं, स्पष्ट कीजिए । झिल्ली के कार्यों का एक सिंहावलोकन प्रस्तुत कीजिए । 15
Answer approach & key points
Framework: UPSC Zoology Paper 2. (a) discuss: intro > 3-4 dimensions > example > balanced close | (b) justify: claim > 3-4 reasons > evidence > conclusion | (c) explain: definition/context > points in order > small example > short close Full marks: Precise definitions, labelled diagrams, specific molecular mechanisms, and named examples.
Phases and checkpoints with cyclin–CDK events (diagram)
MPF (CDK1–cyclin B) with Wee1 and Cdc25 control
Meiotic regulation: prophase I arrest, release, metaphase II arrest by CSF and release at fertilisation
Primary, secondary lysosomes and residual bodies as forms
Diagram of the dynamic system: endocytosis, Golgi hydrolases, autophagy and exocytosis
Functions of lysosomes
Sugar chains only on the outer face
Origin of the asymmetry in the ER and Golgi lumen and vesicle fusion
50MdescribeGenetics, chromosome mutations and Mendelian inheritance
(a) What is chromosome mutation ? Describe various types of polyploidy with suitable examples. Add a note on phenotypic effects of polyploidy. 20
(b) What is chromosome theory of linkage ? Describe the methods for determination of linkage using suitable examples. 15
(c) What is Mendel's dihybrid cross ? Discuss the mechanism of independent assortment using suitable example. 15
हिंदी में पढ़ें
(a) गुणसूत्र उत्परिवर्तन क्या है ? विभिन्न प्रकार की बहुगुणिता (पॉलीप्लॉइडी) का वर्णन उपयुक्त उदाहरणों के साथ कीजिए । बहुगुणिता के लक्षण प्रकृति प्रभावों पर एक टिप्पणी भी लिखिए । 20
(b) सहलग्नता (लिंकेज) का गुणसूत्र सिद्धांत क्या है ? उपयुक्त उदाहरणों का प्रयोग करते हुए सहलग्नता के निर्धारण की विधियों का वर्णन कीजिए । 15
(c) मैंडल का द्विसंकर (डाइहाइब्रिड) क्रॉस क्या है ? स्वतंत्र अपव्यूहन (इंडिपेंडेंट असॉर्टमेंट) की क्रियाविधि की विवेचना उपयुक्त उदाहरण के साथ कीजिए । 15
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) describe: define > structure or process in order > labelled diagram > significance | (c) discuss: intro > 3-4 dimensions > example > balanced close Full marks: Precise definitions, clear mechanisms, specific examples, and correct ratios/calculations.
Definition of chromosome mutation (structure and number)
Autopolyploidy and allopolyploidy with examples (potato, wheat, Raphanobrassica)
Phenotypic effects: gigantism, sterility of odd ploidy, vigour
Linked genes on the same chromosome, complete and incomplete linkage
Test cross and recombination frequency with map units
50MdescribeEvolution, speciation and origin of life
(a) What is isolation ? Describe the major isolating mechanisms which lead to speciation. 20
(b) Enlist theories of origin of life. Explain the theory of biochemical evolution proposed by Oparin and Haldane. 15
(c) What is fossil data ? Discuss the chronological order of human evolution with suitable examples. 15
हिंदी में पढ़ें
(a) पृथक्करण क्या है ? उन प्रमुख पार्थक्य क्रियाविधियों का वर्णन कीजिए जो जाति उद्भवन की ओर ले जाती हैं । 20
(b) जीवन की उत्पत्ति के सिद्धांतों को सूचीबद्ध कीजिए । ओपेरिन एवं हेल्डेन द्वारा प्रस्तावित जैवरासायनिक विकास के सिद्धांत की व्याख्या कीजिए । 15
(c) जीवाश्म डाटा क्या है ? मानव विकास के कालानुक्रमिक क्रम की विवेचना उपयुक्त उदाहरणों के साथ कीजिए । 15
Answer approach & key points
(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: Comprehensive coverage of all parts with precise terminology, clear mechanisms, and specific examples.
Definition of isolation and role in speciation
Pre-zygotic mechanisms with examples
Post-zygotic mechanisms with examples
List of theories (creation, spontaneous generation, panspermia, chemical evolution)
Reducing atmosphere and prebiotic synthesis of organic molecules
Coacervates or protobionts to first cell
Definition of fossil data and dating methods
Sequence: Dryopithecus, Sivapithecus, Australopithecus, Homo habilis, H. erectus, Neanderthal, H. sapiens
Trends such as bipedalism and increase in brain size
50M150wCompulsoryjustifyBiochemistry, physiology and reproductive biology
Write your answer in about 150 words for each of the following : 10×5=50
(a) Fatty acids regulate the nature of lipids, justify. 10
(b) Define coenzyme. Explain the role of coenzymes in the regulation of metabolic reactions by giving suitable examples. 10
(c) Explain the respiratory regulation of acid-base balance. 10
(d) Describe the rapidly acting synaptic transmitters with suitable examples. 10
(e) What is sperm capacitation ? Describe the method of mammalian sperm capacitation in vitro. 10
हिंदी में पढ़ें
निम्नलिखित प्रत्येक के लिए लगभग 150 शब्दों में अपना उत्तर लिखिए : 10×5=50
(a) वसा (लिपिड) की प्रकृति को वसा अम्ल (फैटी एसिड्स) नियंत्रित करते हैं, सिद्ध कीजिए । 10
(b) सहएंजाइम (कोएंजाइम) को परिभाषित कीजिए । उपापचयी अभिक्रियाओं के नियमन में कोएंजाइम की भूमिका की व्याख्या उदाहरण सहित कीजिए । 10
(c) अम्ल-क्षार संतुलन के श्वसन नियमन की व्याख्या कीजिए । 10
(d) तेजी से कार्य करने वाले अंतःप्रदर्शी संचारियों (सायनैप्टिक ट्रांसमिटर्स) का उदाहरणों सहित वर्णन कीजिए । 10
(e) शुक्राणु क्षमतायन (स्पर्म कैपेसिटेशन) क्या है ? पात्रे (इन विट्रो) में स्तनधारी शुक्राणु क्षमतायन विधि का वर्णन कीजिए । 10
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) justify: claim > 3-4 reasons > evidence > conclusion | (b) explain: definition/context > points in order > small example > short close | (c) explain: definition/context > points in order > small example > short close | (d) describe: define > structure or process in order > labelled diagram > significance | (e) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise definitions, specific examples, clear mechanisms, and correct terminology throughout.
Saturation and cis double bonds govern packing and melting point
Chain length effect
Membrane fluidity and its regulation
Definition of coenzyme
NAD+ and FAD as examples
Regulation through coenzyme ratio or availability
CO2 as a volatile acid and the bicarbonate buffer equation
Chemoreceptor control of ventilation
Response to acidosis and alkalosis
Ionotropic receptors and millisecond action
Acetylcholine and glutamate as excitatory examples
GABA or glycine as inhibitory examples
Capacitation as maturation of sperm in the female tract
50MdiscussEndocrinology, signal transduction and bioenergetics
(a) What are peptide hormones ? With the help of schematic diagram, discuss the epinephrine cascade for the glucose release from hepatocytes. 20
(b) Cyclic AMP is a second messenger, justify. Discuss the importance of cyclic AMP in intracellular signal transduction with suitable example. 15
(c) What is bioenergetics ? Discuss the role of second law of thermodynamics in energy transduction. 15
हिंदी में पढ़ें
(a) पेप्टाइड हार्मोन क्या हैं ? व्यवस्था आरेख (स्कीमेटिक डायग्राम) की सहायता से यकृताणुओं (हैपेटोसाइट्स) से ग्लूकोज विमोचन के लिए एपिनेफ्रिन कैस्केड की विवेचना कीजिए । 20
(b) चक्रीय (साइक्लिक) ए.एम.पी. एक द्वितीयक दूत (सेकेंड मैसेंजर) है, सिद्ध कीजिए । अन्तःकोशिक संकेत पारक्रमण (इंट्रासेल्युलर सिग्नल ट्रांसडक्शन) में चक्रीय ए.एम.पी. के महत्व की उपयुक्त उदाहरण सहित विवेचना कीजिए । 15
(c) जैव ऊर्जिकी (बायोएनर्जेटिक्स) क्या है ? ऊर्जा पारक्रमण में उष्मागतिकी के द्वितीय नियम की भूमिका की विवेचना कीजिए । 15
Answer approach & key points
Framework: Zoology, Paper 2. (a) discuss: intro > 3-4 dimensions > example > balanced close | (b) justify: claim > 3-4 reasons > evidence > conclusion | (c) discuss: intro > 3-4 dimensions > example > balanced close Full marks: Comprehensive, accurate, and well-structured answers with clear diagrams and examples.
Peptide hormones as water-soluble messengers acting through surface receptors
Receptor, G protein, adenylyl cyclase, cAMP and PKA
Phosphorylase kinase, glycogen phosphorylase and release of glucose
Hormone as first messenger and cAMP made inside the cell
Properties: diffusion, amplification, termination by phosphodiesterase
Example such as ACTH or glucagon
Definition of bioenergetics and free energy
Second law: increase of entropy of the universe and open systems
Coupling of exergonic and endergonic reactions with ATP
50MexplainPhysiology of digestion, respiration and sensory system
(a) Explain the basic stimuli causing pancreatic secretion. Discuss the role of pancreas in major food digestion. 20
(b) Explain the transport of oxygen in blood. Discuss the factors that shift oxygen-hemoglobin dissociation curve. 15
(c) Describe the functional anatomy of cochlea with suitable diagram. Write down the functions of organ of corti. 15
हिंदी में पढ़ें
(a) अग्न्याशय स्राव पैदा करने वाले मूल उद्दीपनों की व्याख्या कीजिए । प्रमुख खाद्य पाचन में अग्न्याशय की भूमिका की विवेचना कीजिए । 20
(b) रक्त में आक्सीजन के परिवहन की व्याख्या कीजिए । आक्सीजन-हीमोग्लोबिन विमोजन वक्र को स्थानान्तरित करने वाले कारकों की विवेचना कीजिए । 15
(c) कर्णवर्त (कॉक्लिया) की प्रकार्यात्मक शरीर रचना का उपयुक्त आरेख के साथ वर्णन कीजिए । कॉर्टी अंग के कार्यों को स्पष्ट कीजिए । 15
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) explain: definition/context > points in order > small example > short close | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise mechanisms, labelled diagrams, and specific physiological links.
Cephalic, gastric and intestinal phases, with secretin (bicarbonate) and cholecystokinin (enzymes)
Pancreatic amylase, proteases (trypsinogen activated by enteropeptidase) and lipase with colipase and bile salts
Oxyhaemoglobin about 98.5% and dissolved O2 about 1.5%; cooperative binding and sigmoid curve
Right shift by raised pCO2, fall in pH, raised temperature and 2,3-BPG; left shift by the opposite
Three scalae, perilymph and endolymph, and the basilar and Reissner's membranes
Organ of Corti: inner and outer hair cells, tectorial membrane, transduction and amplification
50MdescribeDevelopmental biology, cell communication and gametogenesis
(a) What are morphogens ? Describe the cellular differentiation during morphogenesis. 20
(b) What are gap junction proteins ? Discuss the roles of connexins in cellular interaction. 15
(c) What is primordial germ cell ? With the help of suitable diagram, discuss the process of oogenesis. 15
हिंदी में पढ़ें
(a) आकारजन (मॉर्फोजेनेसिस) क्या है ? आकारजनन के दौरान कोशिकीय विभेदन का वर्णन कीजिए । 20
(b) अन्तराल संधि (गैप जंक्शन) प्रोटीन्स क्या हैं ? कोशिकीय पारस्परिक क्रिया में कनेक्सिन्स की भूमिकाओं की विवेचना कीजिए । 15
(c) प्राइमोर्डियल जनन कोशिका क्या है ? उपयुक्त आरेख की सहायता से अंडजनन प्रक्रिया का वर्णन कीजिए । 15
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) discuss: intro > 3-4 dimensions > example > balanced close Full marks: Precise definitions, detailed mechanisms, and clear, labelled diagrams.
Morphogens as diffusible signals forming concentration gradients that specify fates (Bicoid, Shh, Wnt, BMP)
Sequence of specification, determination and terminal differentiation
Six connexins form a connexon and two connexons dock to form a channel; innexins in invertebrates
Roles: electrical and metabolic coupling, development, with examples such as Cx43 and Cx36
PGC origin and migration to the gonadal ridge
Oogenesis: oogonia, primary oocyte arrested in prophase I, secondary oocyte arrested in metaphase II, polar bodies