For a UPSC CSE aspirant, the optional subject is also an important subject. In the UPSC mains exam, optional marks have two papers, Paper 1 and Paper 2. Each paper is of 250 marks which makes a total of 500 marks. The UPSC optional subject list contains 48 subjects in total, one of which is Zoology.





1. Non-Chordata and Chordata

  • (a) Classification and the relationship of various phyla up to subclasses:
    • Acoelomate and Coelomate, Bilateria and Radiata, Protostomes and Deuterostomes
  • Status of Protista, Onychophora, Parazoa, and Hemichordata
  • Symmetry
  • (b) Protozoa: Locomotion, reproduction, nutrition, sex
  • General features and life history of Paramaecium, Plasmodium, Monocystis, and Leishmania.
  • (c) Porifera: Skeleton, reproduction, and canal system
  • (d) Cnidaria: Polymorphism, defensive structures, and their mechanism
  • Metagenesis
  • Coral reefs and their formation
  • General features and life history of Aurelia, and Obelia
  • (e) Platyhelminthes: Parasitic adaptation
  • General features and life history of Taenia, and Fasciola and their pathogenic symptoms
  • (f) Nemathelminthes: General features, a parasitic adaptation, life history of Wuchereria, and Ascaris
  • (g) Annelida: Coelom and metamerism
  • General features and life history of Nereis, earthworm, and leach
  • Modes of life in polychaetes
  • (h) Arthropoda: Larval forms and parasitism in Crustacea
  • Vision and respiration in arthropods (Prawn, cockroach and scorpion)
  • Metamorphosis in insect and its hormonal regulation, the social behaviour of Apis and termites
  • Modification of mouthparts in insects (cockroach, mosquito, housefly, honey bee and butterfly)
  • (i) Mollusca: Feeding, locomotion, respiration, general features and life history of Lamellidens, Pila and Sepia, torsion and detorsion in gastropods
  • (j) Echinodermata: Feeding, locomotion, respiration, larval forms, general features, and life history of Asterias.
  • (k) Protochordata: Origin of chordates
  • General features and life history of Branchiostoma and Herdmania
  • (l) Pisces: Respiration, migration, and locomotion
  • (m) Amphibia: Origin of tetrapod, pedomorphosis, parental care
  • (n) Reptilia: Origin of reptiles, skull types
  • The status of Sphenodon, and crocodiles
  • (o) Aves: Origin of birds, flight adaptation, migration
  • (p) Mammalia: Origin of mammals, dentition, pouched-mammals, general features of egg-laying mammals, aquatic mammals and primates, endocrine glands (pituitary, thyroid, adrenal, parathyroid, pancreas, gonads) and their interrelationships.
  • (q) Comparative functional anatomy of various systems of vertebrates (integument and its derivatives, endoskeleton, locomotory organs, respiratory system, digestive system, circulatory system including heart and aortic arches, urogenital system, brain and sense organs (eye and ear)

2. Ecology

  • (a) Biosphere: Concept of biosphere
  • Biomes, Human-induced changes in atmosphere including the greenhouse effect, Biogeochemical cycles, biomes and ecotones, community ecology, ecological succession
  • (b) Concept of ecosystem; structure and function of the ecosystem
  • Ecological adaptation
  • Ecological succession
  • Types of ecosystem
  • (c) Population; characteristics, population stabilization, population dynamics
  • (d) Biodiversity and diversity conservation of natural resources.
  • (e) Wildlife of India
  • (f) Remote sensing for sustainable development
  • (g) Environmental biodegradation, pollution, and its impact on the biosphere and its prevention.

3. Ethology

  • (a) Behaviour: Sensory filtering, sign stimuli, responsiveness, learning and memory, habituation, instinct, conditioning, imprinting.
  • (b) Role of hormones in drive
  • The role of pheromones in alarm spreading
  • Crypsis, predator tactics, predator detection, social hierarchies in primates, social organization in insects
  • (c) Orientation, homing, navigation, biological clock, biological rhythms, tidal, seasonal, and circadian rhythms.
  • (d) Methods of studying animal behavior including sexual conflict, kinship, selfishness, and altruism.

4. Economic Zoology:

  • (a) Apiculture, lac culture, carp culture, sericulture, pearl culture, vermiculture, prawn culture
  • (b) Major infectious and communicable diseases (malaria, filaria, tuberculosis, cholera, and AIDS) their vectors, pathogens, and prevention
  • (c) Cattle and livestock diseases, their pathogen (helminthes) and vectors (ticks, Tabanus, mites, Stomoxys)
  • (d) Pests of sugar cane (Pyrilla perpusiella) oil seed (Achaea Janata) and rice (Sitophilus oryzae)
  • (e) Transgenic animals
  • (f) Medical biotechnology, human genetic disease, and genetic counseling, gene therapy
  • (g) Forensic biotechnology

5. Biostatistics

  • Designing of experiments
  • Regression, Correlation, distribution, and measure of central tendency, chi square, student-test, F-test (one-way & two-way F-test)
  • Null hypothesis

6. Instrumentation Methods:

  • (a) Spectrophotometer, phase contrast, and fluorescence microscopy, ultracentrifuge, gel electrophoresis, radioactive tracer, PCR, FISH, ELISA, and chromosome painting
  • (b) Electron microscopy (TEM, SEM)


1. Cell Biology

  • (a) Structure and function of the cell and its organelles (nucleus, mitochondria, plasma membrane, Golgi bodies, ribosomes, endoplasmic reticulum, and lysosomes), cell division (mitosis and meiosis), mitotic spindle and mitotic apparatus, chromosome type polytene, chromosome movements, and lampbrush, organization of chromatin, heterochromatin, Cell cycle regulation
  • (b) Nucleic acid topology, DNA motif, transcription, DNA replication, RNA processing, protein folding, translation, and transport

2. Genetics

  • (a) Modern concept of gene, genetic regulation, split gene, genetic code
  • (b) Sex chromosomes and their evolution, sex determination in Drosophila and man
  • (c) Mendel’s laws of inheritance, linkage, multiple alleles, recombination, genetics of blood groups, hereditary diseases in man, pedigree analysis
  • (d) Mutations and mutagenesis
  • (e) Recombinant DNA technology 
  • Plasmid, cosmid, artificial chromosomes as vectors, transgenic, DNA cloning, and whole animal cloning (principles and methods)
  • (f) Gene regulation and expression in eukaryotes, and prokaryotes
  • (g) Signal molecules, defects in the signaling pathway, cell death, and consequences
  • (h) RFLP, RAPD, and AFLP and application of RFLP in DNA fingerprinting, ribozyme technologies, human genome project, genomics, and proteomics.

3. Evolution

  • (a) Theories of origin of life
  • (b) Theories of evolution; Natural selection, the role of mutations in evolution, molecular drive, evolutionary patterns, mimicry, variation, isolation, and speciation
  • (c) Evolution of elephant, horse, and man using fossil data
  • (d) Hardy-Weinberg Law
  • (e) Continental drift and distribution of animals

4. Systematics

  • Zoological nomenclature, cladistics, molecular taxonomy, international code, and biodiversity

5. Biochemistry

  • (a) Structure and role of carbohydrates, fats, fatty acids and cholesterol, proteins and amino-acids, nucleic acids, Bioenergetics
  • b) Glycolysis and Kreb cycle, oxidation and reduction, energy conservation and release, oxidative phosphorylation, ATP cycle, cyclic AMP – its structure and role
  • (c) Hormone classification (peptide hormones, and steroid), biosynthesis, and functions
  • (d) Enzymes: types and mechanisms of action
  • (e) Vitamins and co-enzymes
  • (f) Immunoglobulin and immunity

6. Physiology (with special reference to mammals)

  • (a) Composition and constituents of blood; blood groups and Rh factor in man, iron metabolism, acid-base balance, factors and mechanism of coagulation, thermo-regulation, anticoagulants
  • (b) Haemoglobin: Composition, types, and role in the transport of oxygen and carbon dioxide
  • (c) Digestion and absorption: Role of salivary glands, liver, pancreas, and intestinal glands
  • (d) Excretion: nephron and regulation of urine formation
  • Osmoregulation and excretory product
  • (e) Muscles: Types, mechanism of contraction of skeletal muscles, effects of exercise on muscles
  • (f) Neuron: nerve impulse – its conduction and synaptic transmission, neurotransmitters
  • (g) Vision, hearing and olfaction in man
  • (h) Physiology of reproduction, puberty and menopause in human

7. Developmental Biology

  • (a) Gametogenesis
  • Spermatogenesis, the composition of semen, in vitro and in vivo capacitation of mammalian sperm, totipotency, Oogenesis
  • Fertilization, morphogen, and morphogenesis, blastogenesis, the establishment of body axes formation, gastrulation in frog and chick, fate map
  • Genes in development in chick, homeotic genes, development of eye and heart, placenta in mammals
  • (b) Cell lineage, cell-to-cell interaction, the role of thyroxine in control of metamorphosis in amphibia, paedogenesis and neoteny, cell death, aging, Genetic and induced teratogenesis
  • (c) Developmental genes in man, in vitro fertilization and embryo transfer, cloning
  • (d) Stem cells: Sources, types and their use in human welfare
  • (e) Biogenetic law
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