All 8 questions from UPSC Civil Services Mains Zoology 2023 Paper II (400 marks total). Every stem reproduced in full, with directive-word analysis, marks, word limits, and answer-approach pointers.
8Questions
400Total marks
2023Year
Paper IIPaper
Topics covered
Biodiversity, RNA processing, continental drift, RFLP, endocytosis (1)t-RNA structure, animal cloning, origin of life (1)Mitochondria, sex determination, gene frequencies (1)Genetic disorders, meiosis, natural selection (1)Digestive hormones, glycolysis, acrosome reaction, neurotransmitters, enzyme inhibition (1)Carbohydrates, haemoglobin, in vitro fertilization (1)Menstrual cycle, B vitamins, oogenesis (1)Enzymes, blood coagulation, neoteny (1)
Write your answer in about 150 words for each of the following:
(a) Write about different ways by which biodiversity is being threatened. (10 marks)
(b) How is hn RNA (primary transcript) modified into functional m-RNA in eukaryotes? Explain. (10 marks)
(c) "Continental drift has resulted in discontinuous distribution of alligators and lungfishes". Justify. (10 marks)
(d) Write principle and application of RFLP. (10 marks)
(e) Describe receptor-mediated endocytosis (RME) along with its advantage. (10 marks)
हिंदी में पढ़ें
निम्नलिखित प्रत्येक के लिए लगभग 150 शब्दों में उत्तर लिखिए:
(a) उन विभिन्न तरीकों के बारे में लिखिए जिनसे जैव-विविधता को खतरा हो रहा है। (10 अंक)
(b) सूकेंद्रिकियों (यूकेरियोट्स) में किस प्रकार से एच एन आर.एन.ए. (प्रारंभिक अनुलेख) कार्यात्मक एम-आर.एन.ए. में परिवर्तित होता है? व्याख्या कीजिए। (10 अंक)
(c) "ऐलिगेटर्स एवं फुफुस मीनों का असंतत वितरण महाद्वीपीय विस्थापन के परिणामस्वरूप हुआ है"। उचित सिद्ध कीजिए। (10 अंक)
(d) आर.एफ.एल.पी. के सिद्धांत एवं इसके प्रयोग के बारे में लिखिए। (10 अंक)
(e) ग्राही-माध्यित अंतःकोशिकता (रिसेप्टर-मीडिएटेड एंडोसाइटोसिस) का वर्णन इसके लाभ सहित कीजिए। (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) explain: definition/context > points in order > small example > short close | (c) justify: claim > 3-4 reasons > evidence > conclusion | (d) write short notes: define > 3-4 key features > one example > one-line significance | (e) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise mechanism, named species, labelled diagrams, conservation links.
Habitat loss and fragmentation
Invasive species and pollution
Population growth and overexploitation
Climate change, IUCN categories
5' cap
3' poly-A tail
Splicing by spliceosome with snRNPs, GU-AG
Alternative splicing and export
Breakup of Pangaea separated ancestral ranges
Alligators in North America and China from Laurasian ancestors
Lungfishes in Australia, South America, Africa from Gondwana
Poor dispersal across salt water and fossil evidence
Restriction site variation changes fragment lengths
50Mdescribet-RNA structure, animal cloning, origin of life
(a) Give structure of t-RNA. Write role of different RNAs in the translation process. (20 marks)
(b) Describe the principle and method of whole animal cloning. (15 marks)
(c) Explain Stanley Miller experiment. In which way, it provided support to most acceptable theory of origin of life? (15 marks)
हिंदी में पढ़ें
(a) टी-आर.एन.ए. की संरचना दीजिए। अनुवाद प्रक्रिया में विभिन्न प्रकार के आर.एन.ए. की भूमिका के बारे में लिखिए। (20 अंक)
(b) संपूर्ण पशु क्लोनन (क्लोनिंग) के सिद्धांत एवं इसकी विधि का वर्णन कीजिए। (15 अंक)
(c) स्टैनले मिलर के प्रयोग की व्याख्या कीजिए। जीवन की उत्पत्ति के सर्वाधिक स्वीकार्य सिद्धांत को इसने किस प्रकार से समर्थन प्रदान किया? (15 अंक)
Answer approach & key points
(a) describe: define > structure or process in order > labelled diagram > significance | (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 diagrams, correct mechanisms, and clear theoretical links.
Cloverleaf with acceptor stem CCA, D arm, anticodon arm, TΨC arm, variable loop
L-shaped tertiary structure and modified bases
Roles of mRNA and tRNA
rRNA: decoding and peptidyl transferase ribozyme
Totipotency of somatic nucleus reprogrammed by egg cytoplasm (SCNT)
Enucleated egg and donor cell fusion
Activation, culture to blastocyst, surrogate transfer
Examples Dolly and Garima II; mitochondrial DNA from egg
Apparatus of two flasks with sparks and condenser
Methane, ammonia, hydrogen, water vapour; one week
Amino acids glycine and alanine formed
Support for Oparin-Haldane chemical evolution; limits
50MdescribeMitochondria, sex determination, gene frequencies
(a) Describe the structure of mitochondrion. Why is it known as powerhouse of the cell? (20 marks)
(b) Explain the mechanism of sex determination in human beings. (15 marks)
(c) Describe various means which result in change in gene frequencies in a population. (15 marks)
हिंदी में पढ़ें
(a) सूत्रकणिका (माइटोकॉन्ड्रियन) की संरचना का वर्णन कीजिए। यह कोशिका का ऊर्जा-घर क्यों जाना जाता है? (20 अंक)
(b) मनुष्यों में लिंग-निर्धारण की क्रियाविधि की व्याख्या कीजिए। (15 अंक)
(c) विभिन्न तरीकों का वर्णन कीजिए जिनके परिणामस्वरूप किसी जनसंख्या में जीन आवृत्तियों में परिवर्तन होता है। (15 अंक)
Answer approach & key points
Framework: UPSC Zoology Paper 2. (a) describe: define > structure or process in order > labelled diagram > significance | (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 anatomical/physiological terminology, labelled diagrams, and clear mechanistic links.
Double membrane, smooth outer, cristae on inner
Elementary particles and ATP synthase; matrix with DNA, 70S ribosomes, Krebs enzymes
Electron transport, proton gradient, chemiosmosis
Most ATP produced by oxidative phosphorylation
XX female, XY male; sperm decides sex
SRY gene on Y makes testis-determining factor
Sertoli AMH and Leydig testosterone
Klinefelter and Turner evidence; X inactivation
Mutation and gene flow
Genetic drift: founder and bottleneck
Natural selection with sickle-cell example
Non-random mating changes genotype not allele frequency
(a) Explain the following: (10×2=20 marks)
(i) Haemophilia
(ii) Red-green colour blindness
(b) Describe various stages of prophase of meiosis-I in an animal cell. (15 marks)
(c) Explain phenomenon of natural selection taking examples of peppered moth and sickle cell anaemia. (15 marks)
हिंदी में पढ़ें
(a) निम्नलिखित की व्याख्या कीजिए: (10×2=20 अंक)
(i) हीमोफीलिया
(ii) लाल-हरी वर्णांधता
(b) एक प्राणिकोशिका में अर्धसूत्री विभाजन-I के प्रोफेज के विभिन्न चरणों का वर्णन कीजिए। (15 अंक)
(c) पेपर्ड शलभ (मोथ) एवं हँसिया कोशिका अरक्तता (सिकल सेल एनीमिया) का उदाहरण लेते हुए प्राकृतिक चयन की घटना की व्याख्या कीजिए। (15 अंक)
Answer approach & key points
Framework: Zoology, Paper 2. (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 definitions, clear mechanisms, accurate diagrams, and strong linkage of examples to theory.
Haemophilia: X-linked recessive, factor VIII or IX deficiency
Carrier female and crosses; affected only females homozygous
Colour blindness: X-linked opsin genes at Xq28; protan and deutan types
Higher prevalence in males; Ishihara test
Leptotene: condensation
Zygotene: synapsis and synaptonemal complex
Pachytene: tetrads and crossing over
Diplotene and diakinesis: chiasmata, terminalisation, envelope breakdown
Definition: differential reproduction of fitter variants
Peppered moth: lichen, soot, carbonaria rise, Kettlewell, decline after clean air
Sickle-cell: Glu to Val; HbS in homozygous harmful
Heterozygote advantage against malaria; balancing selection
Write your answer in about 150 words for each of the following:
(a) Highlight role of various hormones in the regulation of digestive secretions. (10 marks)
(b) Describe the balance sheet of ATP production in glycolysis. (10 marks)
(c) Write a note on acrosome reaction during fertilization. (10 marks)
(d) List different neurotransmitters. Explain the role of specific neurotransmitter across neuromuscular junction. (10 marks)
(e) Explain competitive and non-competitive enzyme inhibition. (10 marks)
हिंदी में पढ़ें
निम्नलिखित प्रत्येक के लिए लगभग 150 शब्दों में उत्तर लिखिए:
(a) पाचन स्राव के नियमन में विभिन्न हार्मोनों की भूमिका पर प्रकाश डालिए। (10 अंक)
(b) ग्लाइकोलाइसिस में ए.टी.पी. उत्पादन के तुलन पत्र (बैलेंस शीट) का वर्णन कीजिए। (10 अंक)
(c) निषेचन के दौरान अग्रापिंडक (एक्रोसोम) प्रतिक्रिया पर एक टिप्पणी लिखिए। (10 अंक)
(d) विभिन्न तंत्रीप्रेषियों (न्यूरोट्रांसमिटर्स) की सूची बनाएं। तंत्रिकापेशीय संधि (न्यूरोमस्कुलर जंक्शन) पर विशिष्ट तंत्रीप्रेषी की भूमिका की व्याख्या कीजिए। (10 अंक)
(e) प्रतिस्पर्धी एवं गैर-प्रतिस्पर्धी प्रकिण्व संदमन की व्याख्या कीजिए। (10 अंक)
Answer approach & key points
Framework: Zoology Paper 2: Define > Structure/Mechanism > Diagram > Example. (a) highlight: name the salient points > one line of substance each > close | (b) describe: define > structure or process in order > labelled diagram > significance | (c) write short notes: define > 3-4 key features > one example > one-line significance | (d) explain: definition/context > points in order > small example > short close | (e) explain: definition/context > points in order > small example > short close Full marks: Precise mechanisms, correct terminology, and clear distinction between concepts.
Gastrin: HCl and pepsinogen
Secretin: bicarbonate-rich pancreatic juice
CCK: enzymes, gall bladder contraction, sphincter of Oddi
GIP and other gut peptides
Two ATP used by hexokinase and PFK
Four ATP by substrate-level phosphorylation
Net two ATP per glucose
NADH and aerobic yield 30-32 ATP
Acrosome holds hyaluronidase and acrosin
ZP3 binding triggers calcium entry
Exocytosis of enzymes and zona penetration
Fusion and block to polyspermy
List: acetylcholine, catecholamines, serotonin, amino acids, peptides, NO
Calcium entry and ACh release
Nicotinic receptor and end-plate potential
Acetylcholinesterase and relaxation
Competitive: binds active site; Vmax same, Km up
Non-competitive: allosteric site; Vmax down, Km same
50MdescribeCarbohydrates, haemoglobin, in vitro fertilization
(a) Classify carbohydrates by giving suitable examples. Also, mention characteristics of each category. (20 marks)
(b) Explain the structure of haemoglobin and its role in carbon dioxide transport. (15 marks)
(c) Describe various techniques of in vitro fertilization. (15 marks)
हिंदी में पढ़ें
(a) उपयुक्त उदाहरण दे कर कार्बोहाइड्रेट्स का वर्गीकरण कीजिए। प्रत्येक श्रेणी की विशेषताओं का भी उल्लेख कीजिए। (20 अंक)
(b) हीमोग्लोबिन की संरचना एवं कार्बनडाइऑक्साइड परिवहन में इसकी भूमिका की व्याख्या कीजिए। (15 अंक)
(c) पात्रे (इन विट्रो) निषेचन की विभिन्न तकनीकों का वर्णन कीजिए। (15 अंक)
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) describe: define > structure or process in order > labelled diagram > significance Full marks: Precise classification, accurate structural details, clear mechanism explanations, correct terminology throughout.
Monosaccharides: glucose, fructose; aldose and ketose; reducing
(a) Give an account of hormonal regulation of menstruation in human females. (20 marks)
(b) Explain the source(s) and functions of the following: (5×3=15 marks)
(i) Vitamin B₁
(ii) Vitamin B₂
(iii) Vitamin B₁₂
(c) Write in detail three phases of oogenesis in human females. (15 marks)
हिंदी में पढ़ें
(a) मानव महिलाओं में माहवारी के हार्मोनल नियमन का विवरण दीजिए। (20 अंक)
(b) निम्नलिखित के स्रोतों एवं कार्यों की व्याख्या कीजिए: (5×3=15 अंक)
(i) विटामिन बी₁
(ii) विटामिन बी₂
(iii) विटामिन बी₁₂
(c) मानव महिलाओं में अंडजनन के तीन चरणों को विस्तार से लिखिए। (15 अंक)
Answer approach & key points
(a) account for: state the phenomenon > the causes in order of weight > conclusion | (b(i)) explain: definition/context > points in order > small example > short close | (b(ii)) explain: definition/context > points in order > small example > short close | (b(iii)) explain: definition/context > points in order > small example > short close | (c) describe: define > structure or process in order > labelled diagram > significance Full marks: Comprehensive, accurate, with diagrams and specific examples
GnRH, FSH, LH from hypothalamus and pituitary
Follicular phase with rising oestrogen and endometrial rebuilding
LH surge from oestrogen positive feedback and ovulation
Luteal phase with progesterone; fall of hormones causes menstruation
Sources: whole grains, pulses, yeast
Thiamine pyrophosphate as coenzyme for pyruvate and alpha-ketoglutarate dehydrogenase and transketolase
Role in energy and nerve function
Deficiency beriberi
Sources: milk, eggs, liver, leafy vegetables
FMN and FAD coenzymes in electron transport and oxidations
Glutathione reductase role
Deficiency angular stomatitis
Sources: animal foods only
Methylmalonyl-CoA mutase and methionine synthase
Needed for DNA synthesis, red cells and myelin; intrinsic factor
Deficiency pernicious anaemia and nerve damage
Multiplication: oogonia, primary oocytes arrest in diplotene
Growth: follicle development under FSH
Maturation: meiosis I completes before ovulation, secondary oocyte at metaphase II
Meiosis II only on fertilisation; one ovum and polar bodies
(a) Explain enzymes, their characteristics as well as induced-fit model of mechanism of enzyme action. (20 marks)
(b) List various coagulation factors and describe their role in blood clotting. (15 marks)
(c) Explain neoteny phenomenon taking suitable example. How is it different from paedogenesis? (15 marks)
हिंदी में पढ़ें
(a) प्रकिण्व एवं उनकी विशेषताओं के साथ-ही-साथ प्रकिण्व की क्रिया-विधि के प्रेरित-अनुरूप मॉडल की व्याख्या कीजिए। (20 अंक)
(b) विभिन्न स्कंदन कारकों की सूची बनाएं एवं रक्त स्कंदन में उनकी भूमिका का वर्णन कीजिए। (15 अंक)
(c) उपयुक्त उदाहरण लेते हुए चिरभूणता परिघटना की व्याख्या कीजिए। यह शावकीजनन से किस प्रकार भिन्न है? (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) enumerate: list the items in order > one line each > no commentary | (c) explain: definition/context > points in order > small example > short close Full marks: Precise definitions, clear mechanisms, labelled diagrams, specific examples, and accurate distinctions.