UPSC Zoology 2024 — Paper I

Framework: Zoology Paper 1: 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: All must items present, named taxa, labelled diagrams, precise terminology

• Coelom as a secondary body cavity lined entirely by mesodermal peritoneum (parietal and visceral layers)
• Acoelomate, pseudocoelomate and eucoelomate grades with examples
• Origin by schizocoely (protostomes) and enterocoely (deuterostomes)
• Functions: suspension of organs, hydrostatic skeleton, independent gut movement, space for organs; divisions in vertebrates
• Definition as a hormone-controlled change of form between juvenile and adult
• Holometaboly: egg–larva–pupa–adult with examples
• Hemimetaboly: egg–nymph–adult with examples (and ametaboly in apterygotes)
• Hormonal control: PTTH, ecdysone and juvenile hormone
• Location and structure: bilobed gland with isthmus, follicles with colloid, parafollicular C cells
• Hormones T3, T4 (iodine-dependent) and calcitonin
• Functions: BMR, thermogenesis, growth and brain development, calcium regulation
• Disorders (cretinism, myxoedema, goitre, Graves'/hyperthyroidism) and HPT-axis feedback
• Pre-erythrocytic asexual multiplication of Plasmodium in liver cells
• Sporozoites → cryptozoites → schizont → cryptomerozoites
• Exo-erythrocytic cycle (metacryptozoites) and hypnozoites in P. vivax/P. ovale causing relapse
• Merozoites released to start erythrocytic schizogony; duration differs by species
• Groups: Cetacea, Sirenia, Pinnipedia (and others such as sea otter)
• Morphological adaptations: streamlined body, flippers, flukes, reduced hair, blubber
• Physiological adaptations: diving reflex, bradycardia, high myoglobin, countercurrent heat exchange, echolocation
• Retained mammalian features and convergence with fishes; Indian example (Ganges river dolphin)

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) compare: paired headings or point-wise contrast > key differences > significance > conclusion Full marks: Precise taxonomic placement, detailed labelled diagrams, clear mechanisms, and specific examples.

• General features: dorsoventrally flattened, leaf-like digenean with tegument and spines, oral and ventral suckers, bifurcated blind gut, flame cells, hermaphrodite
• Digenetic life cycle: operculate egg → miracidium → sporocyst → redia → cercaria in Lymnaea → metacercaria on vegetation
• Infection by ingestion of metacercariae; migration through gut wall, peritoneal cavity and liver to bile ducts
• Pathogenicity: acute migratory hepatic damage and chronic cholangitis/biliary fibrosis, anaemia, economic loss; control
• Definition: self-fertilisation within one individual, fusion of two gametic nuclei from the same micronucleus
• Meiosis of both micronuclei, degeneration of most products, mitosis of one to form two pronuclei
• Fusion into a homozygous synkaryon; old macronucleus disintegrates; new macro- and micronuclei formed and distributed at fission
• Significance: complete homozygosity, reproduction without a mate, rejuvenation of the clone
• Telencephalon derives from the prosencephalon: pallium (dorsal) and subpallium (corpus striatum)
• Cyclostomes and fishes: small, olfactory-dominated; evagination in sharks/lungfish, eversion in teleosts
• Amphibians and reptiles: evaginated hemispheres, archipallium/paleopallium, primordial neopallium (dorsal cortex) in reptiles
• Birds: pallial DVR and Wulst dominate; mammals: neocortex dominant, corpus callosum in eutherians, reduced olfactory lobes

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: All musts met, 3+ credits, 1+ bonus, accurate diagrams

• Nauplius: unsegmented, median eye, three pairs of appendages (antennules, antennae, mandibles)
• Metanauplius and protozoea: added appendages and differentiation of thorax
• Zoea (carapace, stalked eyes, maxillipeds for swimming), mysis (schizopod thoracic exopodites, pleopods, uropods) and megalopa of decapods
• Other larvae (cypris of barnacles, phyllosoma of Palinurus, alima/erichthus of Squilla) and group-wise sequences
• Definition: calcareous structures built by hermatypic scleractinian corals with zooxanthellae in warm, clear, shallow seas
• Types: fringing, barrier and atoll with Indian examples
• Darwin's subsidence theory with evidence and criticism
• Daly's glacial-control and Murray's standstill theories, and the Enewetak drilling evidence
• Invertebrate excretory organs: flame cells/protonephridia, metanephridia, Malpighian tubules, green glands
• Vertebrate sequence pronephros → mesonephros/opisthonephros → metanephros with origin from intermediate mesoderm
• Functional changes: glomerular filtration, tubular reabsorption, osmoregulation in freshwater vs marine fishes
• Metanephros and loop of Henle for concentrated urine; shift ammonotelic → ureotelic → uricotelic with habitat

(a) account for: state the phenomenon > the causes in order of weight > conclusion | (b) 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, well-illustrated answers with precise terminology and clear mechanisms.

• Structure: ectodermal epidermis, mesodermal dermis, hypodermis with functions
• Class-wise account: mucous skin and scales of fishes, glandular skin of amphibians, keratinised scales of reptiles, feathers of birds, hair and glands of mammals
• Epidermal derivatives (hair, feathers, horny scales, claws, nails, hooves, horn sheath, beaks, glands) vs dermal derivatives (fish scales, osteoderms, antlers, dermal bones)
• Types of fish scales (placoid, ganoid, cosmoid, cycloid, ctenoid) and functions of integument
• Definition: occurrence of structurally and functionally different individuals (zooids) in one species, with division of labour
• Obelia colony: gastrozooids (hydranths) and gonozooids (blastostyles in gonotheca); medusa as third form (trimorphic)
• Life cycle: blastostyle buds medusae → dioecious medusae release gametes → zygote → planula → new colony
• Metagenesis: alternation of asexual polyp and sexual medusa (both diploid)
• A pair of bipectinate ctenidia in the mantle cavity with lamellae providing large surface
• Muscular ventilation: radial muscles expand cavity (inflow), circular muscles contract with locking cartilages (outflow through funnel)
• Blood circuit: branchial hearts pump haemocyanin-containing blood through gills to systemic heart
• Counter-current flow of water and blood maintains the diffusion gradient; link with jet propulsion

Framework: Zoology Paper 1: 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 definitions, clear mechanisms, specific examples, and labelled diagrams where appropriate.

• Definition: interlocking network of food chains in a community
• Trophic levels from producers to top consumers and decomposers; grazing and detritus pathways
• Stability through alternative pathways; ~10% energy transfer
• Example of a real food web (e.g. pond, grassland or mangrove) with diagram
• Definition: endogenous, self-sustaining periodic changes entrained by zeitgebers
• Types: circadian, circatidal/circalunar, circannual (ultradian, infradian)
• Mechanism: SCN master clock, pineal melatonin; CLOCK–BMAL1 and PER–CRY transcription–translation feedback loop
• Adaptive significance with examples (migration, breeding, tidal activity)
• Causative agent HIV: enveloped retrovirus (lentivirus), RNA genome, reverse transcriptase
• Infection of CD4+ T cells via gp120–CD4 and CCR5/CXCR4; integration as provirus
• Modes of transmission and progressive CD4 decline leading to opportunistic infections
• Diagnosis/treatment (ELISA/NAT, ART) and India's control measures (NACO, NACP, 2017 Act)
• FISH-based technique using whole-chromosome fluorescent probes
• Probe preparation by flow sorting/microdissection and DOP-PCR labelling
• Hybridisation to metaphase chromosomes and visualisation of each chromosome in distinct colour; SKY/M-FISH
• Applications: detection of translocations and marker chromosomes in cancer and clinical cytogenetics; Zoo-FISH in evolution
• Definition: IUCN documentation of threatened species (first published 1966)
• IUCN categories EX, EW, CR, EN, VU, NT, LC, DD (NE) with criteria
• Indian context: ZSI/BSI Red Data Books and Indian examples
• Uses: conservation priority, legal protection (Wild Life (Protection) Act, 1972), recovery plans

Framework: Ecological Succession & Ethology. (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 definitions, clear distinction of theories, specific examples, and detailed polyculture mechanism.

• Definition: orderly, directional change in community composition leading to a climax; seral stages and pioneer community
• Types: primary vs secondary, autogenic vs allogenic, autotrophic vs heterotrophic, hydrosere/xerosere (lithosere, psammosere) with stages
• Climax theories: Clements' monoclimax, Tansley's polyclimax, Whittaker's climax pattern; Gleason's individualistic concept
• Mechanisms: Connell–Slatyer facilitation, tolerance and inhibition; Egler's relay vs initial floristics; Odum's trends
• Aggression: threat, attack and defence; offensive vs defensive; intra- and interspecific
• Ritualised aggression and displays that limit injury, with examples (stags, Betta, stickleback)
• Territoriality: defended area; Nice's types A–D with examples; marking by song, scent, display
• Costs and benefits of territoriality; dominance hierarchies (pecking order)
• Indian major carps: Catla catla, Labeo rohita, Cirrhinus mrigala (Labeo calbasu as minor)
• Feeding niches: catla surface zooplankton, rohu column, mrigal bottom detritus; rationale of polyculture
• Composite fish culture with exotic silver, grass and common carps; stocking density and ratios
• Pond management: eradication of predators/weeds, liming, fertilisation, supplementary feeding, induced breeding for seed, harvesting and yields

Framework: Zoology, Paper 1. (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 taxon names, labelled diagrams, specific mechanisms, and clear linkage to vectors or conservation.

• Plasmodium species (falciparum, vivax, malariae, ovale, knowlesi) and transmission by female Anopheles (also blood transfusion, congenital)
• Life cycle outline: hepatic and erythrocytic schizogony in man, sporogony in mosquito
• Symptoms (periodic paroxysms, anaemia, splenomegaly; complications of falciparum) and diagnosis (smear microscopy, RDT, PCR)
• Treatment (ACT, artesunate, primaquine with G6PD test) and prevention (ITNs, IRS, larval control, vaccines RTS,S/R21, NFME 2016–2030)
• Principle: absorption of UV/visible light by chromophores via electronic transitions; Beer–Lambert law A=εcl
• Components: deuterium and tungsten sources, monochromator, cuvette (quartz for UV), detector, readout; single vs double beam
• Procedure: blank, λmax selection, standard curve
• Applications: quantitation of proteins (280 nm) and nucleic acids (260 nm, 260/280 purity), enzyme kinetics, clinical and pharmaceutical analysis
• Mechanoreceptors: cutaneous receptors, hair cells, lateral line, insect sensilla and chordotonal organs, proprioceptors
• Mechanotransduction: deformation opens mechanically gated channels (tip links, Piezo) producing receptor potentials
• Olfaction in vertebrates: odorant GPCRs, Golf–cAMP–CNG channel cascade, olfactory bulb glomeruli; vomeronasal organ for pheromones
• Olfaction in insects: antennal sensilla, odorant-binding proteins, ionotropic ORs, pheromones and behaviour

(a) discuss: intro > 3-4 dimensions > example > balanced close | (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 definitions, clear examples, and detailed biological mechanisms.

• Arithmetic mean, geometric mean, harmonic mean, median and mode with formulas
• Worked biological example computing the measures
• Merits and demerits of each (use of all values, effect of extremes, suitability for rates, skewed or nominal data)
• Relationship HM ≤ GM ≤ AM and mean–median–mode in skewed distributions
• Definition: group of interbreeding individuals of a species in a given area and time
• Density (crude and ecological), natality and mortality, immigration and emigration
• Age structure (pyramids) and sex ratio; dispersion patterns (clumped, uniform, random)
• Biotic potential, growth forms (J and S curves), carrying capacity, r- and K-selection
• Correct systematic position of the chosen pest (e.g. Lipaphis erysimi: Insecta, Hemiptera, Aphididae)
• Life cycle: parthenogenetic viviparous reproduction, nymphal instars, apterous and alate forms, many generations in winter
• Damage: sap sucking of shoots, flowers and pods, leaf curling, honeydew and sooty mould, virus transmission, yield loss
• IPM control: early sowing, tolerant varieties, conservation of coccinellids, syrphids, Chrysoperla and Diaeretiella, need-based insecticides at ETL