UPSC Zoology 2022 — Paper I

Framework: Zoology Paper 1: 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) describe: define > structure or process in order > labelled diagram > significance | (d) justify: claim > 3-4 reasons > evidence > conclusion | (e) explain: definition/context > points in order > small example > short close Full marks: All five notes accurate and about 150 words each: ommatidium structure with two ocelli, five types of symmetry with examples, four islet cell types with hormones and actions, nematocyst mechanism as defence, and Sphenodon as a mosaic living fossil.

• Pair of compound eyes made of about 2,000 ommatidia, with the cornea, crystalline cone, retinula cells and rhabdom of an ommatidium
• Two ocelli (fenestrae), simple eyes that form no image
• Mosaic (apposition) vision with pigment isolating the ommatidia
• Definition: division into similar halves by a plane or planes through the body axis
• Radial and bilateral symmetry with the planes involved and examples
• Asymmetry, spherical and biradial symmetry with examples
• Islets of Langerhans as scattered endocrine clusters (1–2% of the pancreas) among the exocrine acini
• α, β, δ and PP cells with the hormone each secretes
• Actions of insulin and glucagon on blood glucose
• Structure of the cnidoblast and nematocyst (capsule, operculum, coiled thread, cnidocil)
• Discharge on stimulation (water entry by osmosis, pressure rise, eversion of the thread)
• Nematocyst types and how they pierce, paralyse, entangle or stick to an attacker
• Only living member of Rhynchocephalia, a living fossil with Mesozoic (Triassic) ancestry
• Primitive features: diapsid skull with both temporal arches, amphicoelous vertebrae, gastralia, parietal eye
• Relationship to Squamata (Lepidosauria) and specialised features such as acrodont teeth

Framework: Zoology Paper 1: 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: Full conjugation sequence with nuclear dimorphism, distinct features of monotremes, marsupials and aquatic mammals, and five scale types with labelled diagrams and examples.

• Binary fission: mitosis of the micronucleus, amitosis of the macronucleus, transverse division of the cell
• Conjugation sequence: meiosis of micronuclei, stationary and migratory pronuclei, exchange, synkaryon, exconjugants
• Roles of macronucleus and micronucleus (nuclear dimorphism)
• Monotremes: eggs, cloaca, no teats, with examples (Ornithorhynchus, Tachyglossus)
• Marsupials: very short gestation, undeveloped young, pouch with teats, epipubic bones, with examples
• Aquatic mammals: cetaceans, sirenians and pinnipeds with streamlining, blubber, flippers, blowhole or flukes
• Placoid, cosmoid, ganoid, cycloid and ctenoid scales named and distinguished
• Structure of each type (layers or margin) with the fish group that has it
• Labelled diagrams of the scale types

Framework: Zoology Paper 1: 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: Complete Wuchereria life cycle with periodicity and features, three canal types with water path and functions, and a well-labelled eye diagram with coats, retina, lens and humours.

• Habitat and habits: adults in human lymphatics, sheathed microfilariae in blood with nocturnal periodicity, Culex as vector
• General features: thread-like dioecious nematode, sexual dimorphism, male with curved tail and spicules, sheathed microfilaria
• Life cycle: mosquito phase (L1 sausage stage, L2, infective L3 in the proboscis) and human phase (L3 through the bite wound, adults in lymphatics)
• Asconoid, syconoid and leuconoid types with examples
• Water path through each type (ostia, spongocoel, canals, chambers, osculum)
• Functions: feeding, respiration, excretion and reproduction
• Labelled diagram of the eyeball with cornea, sclera, choroid, retina, iris, pupil, lens and humours
• The three coats (fibrous, vascular, retina) and their parts
• Retina with rods and cones, fovea and blind spot

Framework: Zoology Paper 1: 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) describe: define > structure or process in order > labelled diagram > significance Full marks: Reptile origin with the amniotic egg, skull-based groups and Mesozoic radiation; tooth structure with all three classifications; Herdmania features and development through the tadpole larva and retrogressive metamorphosis.

• Origin from amphibian (reptiliomorph) ancestors in the Late Carboniferous, with the amniotic egg and dry scaly skin as the key advances
• Cotylosaurs as stem reptiles and radiation into groups by temporal openings (anapsid, synapsid, diapsid, euryapsid)
• Mesozoic radiation into land, air and sea habitats, and the surviving orders (Testudines, Crocodilia, Squamata, Rhynchocephalia)
• Structure: crown, neck and root with enamel, dentine, pulp cavity and cementum
• Classification by shape: heterodont (incisor, canine, premolar, molar), with homodont teeth and crown patterns
• Classification by attachment (thecodont, pleurodont, acrodont) and by succession (monophyodont, diphyodont, polyphyodont)
• Habitat and habits: marine, attached to hard surfaces, sedentary filter feeder
• General features: tunic, two siphons, branchial sac with stigmata and endostyle, hermaphrodite
• Development: external fertilisation, tadpole larva with notochord and nerve cord, retrogressive metamorphosis

Framework: Zoology Paper 1. (a) explain: definition/context > points in order > small example > short close | (b) comment: context > arguments both sides > judgment > close | (c) describe: define > structure or process in order > labelled diagram > significance | (d) explain: definition/context > points in order > small example > short close | (e) compare: paired headings or table > key differences > significance > conclusion Full marks: Precise definitions, specific examples, and clear mechanisms for all parts.

• Ecotone defined as a transition zone between two adjacent communities, with species of both and some edge species
• At least two correct examples (forest–grassland, mangrove, estuary, marsh or lake margin, tree line)
• Edge effect: higher species diversity and density at the junction than in either community
• Arithmetic mean, median and mode defined with formulas
• Merits and limits of each (mean distorted by outliers, median for skewed data, mode for most frequent value)
• Choice of measure or relation among them (symmetrical vs skewed data; Mode ≈ 3 Median − 2 Mean)
• Principle: charged molecules separate in an electric field through a gel sieve, DNA by size
• Steps: gel with wells in buffer, samples with loading dye and marker, current, DNA towards the anode, staining and UV visualisation
• Applications: DNA fingerprinting, PCR and restriction products, protein analysis
• Definition: associative learning linking a stimulus or an act with its consequence
• Classical (Pavlovian) conditioning with US, UR, CS, CR and the bell–food–dog example
• Operant (instrumental) conditioning with reinforcement (Thorndike, Skinner box)
• Klinefelter's: 47,XXY male; tall, small testes, sterile, gynaecomastia
• Turner's: 45,X female; short, webbed neck, streak gonads, primary amenorrhoea
• Origin by nondisjunction of sex chromosomes; one Barr body in Klinefelter's, none in Turner's

Framework: Zoology Paper 1: Define > Structure/Mechanism > Diagram > Example. (a) describe: define > structure or process in order > labelled diagram > significance | (b(i)) compare: paired headings or table > key differences > significance > conclusion | (b(ii)) explain: definition/context > points in order > small example > short close | (c) explain: definition/context > points in order > small example > short close Full marks: Precise definitions, specific examples, clear mechanisms, and accurate applications.

• At least four types of primate social groups, each with a correct example (solitary, monogamous pair, one-male, multi-male multi-female, fission–fusion, multi-level, one-female)
• Defining feature of each type (composition and mating system)
• Importance: predator protection, food and territory, mates and infant care, social learning
• Primary pollutants are emitted directly; secondary pollutants form in the atmosphere from primary ones by chemical or photochemical reactions
• Correct examples of both (CO, SO₂, soot against ozone, PAN, sulphuric and nitric acids)
• Primary treatment is physical: screening, grit removal, sedimentation
• Secondary treatment is biological: aeration tank, aerobic microbial flocs, fall in BOD
• Settling as activated sludge, return of part as inoculum, anaerobic digestion of the rest to biogas
• χ² = Σ(O − E)²/E with null hypothesis and degrees of freedom
• Decision rule: compare with the table value at P = 0.05 and reject the null hypothesis if the calculated χ² is larger
• At least two biological applications (Mendelian ratios, linkage or independent assortment, Hardy–Weinberg equilibrium, association of attributes)

Framework: Zoology, Paper 1. (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, specific examples, and correct terminology throughout.

• Biodiversity defined with its genetic, species and ecosystem levels
• In situ conservation defined as protection of species in their natural habitats
• At least four in situ means with examples (national parks, wildlife sanctuaries, biosphere reserves, conservation and community reserves, sacred groves, species projects)
• Two laws (Thorndike's law of effect and law of exercise) correctly stated
• Habituation defined as a non-associative decline of response, with an example
• Trial and error learning (puzzle box) and latent learning (Tolman and Honzik maze) each defined with an example
• Principle: primer-directed copying of target DNA by a heat-stable polymerase in repeated cycles
• Three steps with temperatures: denaturation 94–95 °C, annealing 50–65 °C, extension 72 °C
• Components (template, two primers, dNTPs, Taq polymerase, Mg²⁺ buffer) and at least three uses

(a) describe: define > structure or process in order > labelled diagram > significance | (b) explain: definition/context > points in order > small example > short close | (c) explain: definition/context > points in order > small example > short close Full marks: Precise scientific terminology, clear mechanisms, and specific examples for all parts.

• Causative agent Mycobacterium tuberculosis (acid-fast bacillus) and airborne droplet-nuclei spread
• Symptoms and diagnosis: chronic cough, fever, weight loss; sputum smear, culture, molecular tests (CBNAAT/Xpert), chest X-ray, Mantoux
• Treatment and prevention: DOTS with HRZE for 2 months then HR for 4 months, second-line drugs for MDR-TB; BCG, early treatment, contact tracing
• Biological fixation by nitrogenase in prokaryotes, with symbiotic, free-living and associative examples
• Non-biological fixation by lightning (N₂ + O₂ → NO → nitrate)
• Industrial fixation: Haber–Bosch process, N₂ + 3H₂ ⇌ 2NH₃, iron catalyst, high temperature and pressure
• Gene therapy defined as introducing or correcting genes in a patient's cells, with the role of vectors
• Germline therapy: changes gametes or embryo, heritable, ethically restricted
• Somatic therapy: not inherited; ex vivo and in vivo types with named examples (ADA-SCID, CAR-T, Luxturna, Zolgensma, Casgevy)