ISC Class 12 Biology Syllabus 2026-27
CISCE has released the ISC Class 12 Biology Syllabus for the academic session 2026-27. The syllabus defines the unit-wise topics, practical work, and exam structure for the board examination.
Students should review the ISC 12th Biology Syllabus 2026-27 before starting preparation. The document helps students understand topic distribution, internal assessment criteria, and question paper pattern.
Teachers should align classroom teaching with the updated ISC Biology curriculum prescribed by CISCE.
Oswal Publishers has updated its ISC Class 12 Biology books according to the latest CISCE syllabus and exam pattern.
Students can download the ISC Class 12 Biology Syllabus 2026-27 PDF from the link below for accurate and structured exam preparation.
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ISC Biology Class 12 Latest Syllabus 2026-27
There will be two papers in the subject:
Paper I: Theory: 3 hours ... 70 marks
Paper II: Practical: 3 hours ... 15 marks
Project Work … 10 marks
Practical File … 5 marks
Paper I – Theory
70 Marks
1. Reproduction
(i) Sexual reproduction in flowering plants
Flower structure; development of male andfemale gametophytes; pollination - types,agencies and examples; outbreedingdevices; pollen-pistil interaction; artificialhybridisation,double fertilization; postfertilization events - development ofendosperm and embryo, development ofseed and formation of fruit; special modes -apomixis, parthenocarpy, polyembryony;Significance of seed dispersal and fruitformation.
Pre-fertilisation structures and events.
Structure of microsporangium, T.S. of anthermicrosporogenesis, structure anddevelopment of pollen grain, viability ofpollen grain, economic importance of pollengrain. Pistil – structure of megasporangium(L.S. of anatropous ovule),megasporogenesis, structure anddevelopment of female gametophyte.
Types of pollination (autogamy,chasmogamy, cleistogamy, geitonogamy,xenogamy), adaptations in flowerspollinated by wind, water and insects.Advantages of self and cross-pollination.Contrivances for prevention of self-pollination. Pollen-pistil interaction in termsof incompatibility/compatibility, eventsleading to fertilisation, artificialhybridisation: procedure (emasculation andbagging), and its significance in plantbreeding); definition of triple fusion anddouble fertilization, significance of doublefertilisation, changes in the ovary and ovulefor seed and fruit formation; apomixis,polyembryony, parthenocarpy to beexplained briefly. Fruits to be classified intotrue and false, structure (L.S) of a typicalfruit (mango and coconut); Internalstructure of dicot (bean) and monocot(maize) seeds; definition, differences andexamples of albuminous and non-albuminous seeds. Significance of seed andfruit formation. Significance of dispersal of seeds.
Post-fertilisation events - embryo formation (monocot and dicot); types of endosperm (cellular, nuclear and helobial); definition of perisperm.
(ii) Human Reproduction
Male and female reproductive systems;microscopic anatomy of testis and ovary; gametogenesis - spermatogenesis andoogenesis; menstrual cycle; fertilisation,embryo development upto blastocystformation, implantation; pregnancy andplacenta formation (elementary idea);parturition (elementary idea); lactation(elementary idea).
Organs of male and female reproductivesystem and their functions; internal structureof testis and ovary to be taught with the helpof diagrams; gametogenesis- spermatogenesis (including spermiogenesis and spermiation) oogenesis; hormonal control of gametogenesis, structure of sperm and mature ovum, menstrual cycle - different phases and hormone action, differences between oestrous and menstrual cycle, menarche and menopause, physico-chemical events during fertilisation, implantation, embryonic development up to blastocyst formation, important features of human embryonic development (formation of heart, limbs, digits, appearance of hair on head, eyelashes, separation of eye lids, external genital organs and first movement of foetus with reference to time period) placenta and its functions (structure and the types of placenta not required). Parturition; lactation – hormonal control and importance.
(iii) Reproductive Health
Need for reproductive health and preventionof Sexually Transmitted Diseases (STDs);birth control - need and methods,contraception and medical termination ofpregnancy (MTP); amniocentesis; infertilityand assisted reproductive technologies(elementary idea for general awareness).
Definition of reproductive health, programs ofreproductive health (family planning, RCH), population explosion - role of government in controlling the population, contraceptives methods and their methods of action (natural-periodic abstinence, withdrawal or coitus interruptus, lactational amenorrhea; artificial –barriers, IUDs, oral pills, spermicidalagents, implants and surgical methods,definition of medical termination ofpregnancy (MTP) and reasons for it; causesof infertility. Amniocentesis and its role indetecting genetic defects. Assistedreproductive technologies: IVF, IUT, ZIFT,ICSI, GIFT, AI, IUI. - definition andapplication only. Causes, symptoms andmethods of prevention of sexually transmitteddiseases (genital warts, genital herpes,hepatitis- B, AIDS gonorrhoea, syphilis,chlamydiasis, trichomoniasis).
2. Genetics and Evolution
(i) Principles of inheritance and variation
Heredity and variation: Mendelianinheritance; deviations from Mendelism -incomplete dominance, co-dominance,multiple alleles and inheritance of bloodgroups, pleiotropy; elementary idea ofpolygenic inheritance; chromosomal theoryof inheritance; sex determination; linkageand crossing over; mutation; sex linkedinheritance; Mendelian disorders in humans;chromosomal disorders in humans.
Explanation of the terms heredity andvariation; Mendel's Principles of inheritance;reasons for Mendel's success; Biologicalimportance of Mendelism; definition ofhomologous chromosomes, autosomes andsex chromosomes; alleles – dominant andrecessive; phenotype; genotype; homozygous; heterozygous, monohybrid and dihybridcrosses; back cross and test cross, definitionsto be taught with simple examples usingPunnett square. Incomplete dominance withexamples from plants (snapdragon -Antirrhinum). Co-dominanceand multiple allelism – (pattern of inheritanceof ABO blood group in humans), polygenicinheritance with an example of inheritance ofskin colour in humans (students should betaught examples from human genetics throughpedigree charts. They should be able to create createa pedigree chart and interpret the patterns of inheritance by analysis of pedigree chart). Pleiotropy with reference to the example of Phenylketonuria (PKU) in human beings and starch synthesis in pea seeds. Chromosomal theory of inheritance; sex determination in humans, birds, honey bees and grasshopper, sex-linked inheritance - with reference to Drosophila (colour of body-yellow and brown; and colour of eyes-red and white), and man (haemophilia and colour blindness), definition and significance of linkage and crossing over. Mutation: spontaneous, induced, gene (point – transition, transversion and frame-shift); human genetic disorders: phenylketonuria, thalassaemia, colour blindness, sickle cell anaemia; chromosomal disorders: Down’s syndrome, Klinefelter’s syndrome, Turner’s syndrome.
(ii) Molecular basis of Inheritance
Search for genetic material; structure ofDNA and RNA; DNA packaging; DNAreplication; central dogma; transcription,genetic code, translation; regulation ofgene expression - lac operon; humangenome project; DNA fingerprinting.
Structure of eukaryotic chromosomes withreference to nucleosome; properties of idealgenetic material such as ability to replicate,chemical stability, mutability andinheritability. Search for DNA as geneticmaterial - Griffith’s experiment, Hershey andChase’s experiment, Avery, McLeod andMcCarty’s experiment; double helical modelof DNA (contributions of Miescher, Watsonand Crick, Wilkins, Franklin and Chargaff);Differences between DNA and RNA; types ofRNA (tRNA, mRNA and rRNA, snRNA,hnRNA); central dogma; reversetranscription (basic idea only), replication ofDNA (role of enzymes, namely DNApolymerase and ligase), Meselson and Stahl’sexperiment, and Taylor’s experiment.transcription, post-transcriptional processingin eukaryotes (splicing, capping and tailing).Intron, exon, cistron, recon, muton,monocistronic and polycistronic transcriptionunit (definitions only). Discovery andessential features of genetic code. Definitionof codon. Protein synthesis - translation in prokaryotes. Gene expression; lac operon in E. coli.
Human Genome Project: goal; methodologies [Expressed Sequence Tags (EST), Sequence Annotation], salient features and applications. DNA finger printing – technique, application and ethical issues to be discussed briefly.
(iii) Evolution
Origin of life; biological evolution andevidences for biological evolution(palaeontology, comparative anatomy,embryology and molecular evidences);Darwin's contribution, modern synthetictheory of evolution; mechanism ofevolution - variation and natural selectionwith examples, types of natural selection;gene flow and genetic drift; Hardy -Weinberg's principle; adaptive radiation;human evolution.
Origin of life - abiogenesis and biogenesis,effect of oxygen on origin of life to show thatreducing atmosphere is essential for abioticsynthesis. Important views on the origin of life(panspermia, spontaneous generation),modern concept of origin of life, OparinHaldane theory (definition of protobionts,coacervates); Miller and Urey experiment.Evidences of evolution: morphologicalevidences, definition and differences betweenhomologous and analogous organs (twoexamples each from plants and animals),convergent evolution and divergent evolution,vestigial organs; Embryological evidences –theory of recapitulation, definition anddifferences between ontogeny and phylogeny.Palaeontological evidence – definition offossils and radioactive carbon-dating.Geological time scale (with reference todominant flora and fauna) Biogeographicalevidence – definition of biogeography,molecular (genetic) evidences -for examplegenome similarity, universal genetic code;Darwin's finches and marsupials (adaptiveradiation).
Darwinism: salient features of Darwinism,contribution of Malthus. Examples of naturalselection – Long neck of giraffe, industrialmelanism, resistance of mosquitoes to DDTand resistance of bacteria to antibiotics, Lederberg’s replica plating experiment, criticism of Darwinism. Neo-Darwinism (Modern Synthetic Theory); gene migration or gene flow, genetic drift (Founder’s effect, bottle-neck effect), mutation, genetic recombination and natural selection, Hugo de Vries theory of mutation - role of mutation in evolution; Hardy Weinberg’s principle, factors affecting Hardy Weinberg equilibrium (numericals on Hardy Weinberg equilibrium), Variation - causes of variation (mutation and recombination), types of natural selection (directional, disruptive and stabilizing). Evolution of man - three features (for example cranial capacity, height, posture, dentition, social behaviour, etc.) of each of the ancestors Dryopithecus, Ramapithecus, Australopithecus, Homo habilis, Homo erectus, Homo neanderthalensis, Cro-magnon man leading to man of today (Homo sapiens sapiens).
3. Biology and Human Welfare
(i) Human Health and Diseases
Pathogens; parasites causing human diseases(viruses, bacteria, protozoans, helminths,and fungi);Basic concepts of immunology -vaccines; cancer, HIV and AIDS;Adolescence - drug and alcohol abuse.
Communicable diseases; modes oftransmission, causative agents, symptomsand prevention; viral diseases (commoncold, chikungunya and dengue), bacterialdiseases (typhoid- diagnosed by Widal test,pneumonia, diphtheria and plague),protozoal diseases (amoebiasis, andmalaria, graphic outline of life cycle ofPlasmodium), helmintic diseases(ascariasis, and filariasis); fungal(ringworms); cancer - types of tumour(benign, malignant), causes, diagnosis andtreatment (surgery, immunotherapy, andradiotherapy), characteristics of cancercells (loss of contact inhibition andmetastasis); allergies and allergens –definition and general symptoms of allergies.
Immunity (definition and types – innateimmunity - role of physical barriers,
physiological barriers, cellular barriers, and cytokine barriers; and acquired, active and passive, humoral and cell-mediated), Interferons – definition, source and function; structure of a typical antibody molecule, types of antibodies - IgG, IgA, IgM, IgD and IgE (function and occurrence, e,g. in serum, saliva, colostrum); vaccination and immunisation; autoimmunity, primary and secondary lymphoid organs and tissues, brief idea of AIDS – causative agent (HIV), modes of transmission, diagnosis (ELISA), symptoms, replication of retrovirus in the infected human cell (including diagram) and prevention.
Alcoholism and smoking - effects on health.
Drugs: effects and sources of opioids, cannabinoids, cocaine and barbiturates.
Reasons for addiction; prevention and control of alcohol and drug abuse.
(ii)Microbes in Human Welfare
In household food processing, industrialproduction, sewage treatment, energygeneration and microbes as biocontrolagents and biofertilisers. Antibiotics.
Use of microbes in: (i) Household products:Lactobacillus (curd), Saccharomyces(bread), Propionibacterium (Swiss cheese); (ii)Industrial products: beverages (with andwithout distillation), antibiotics (Penicillin –discovery and use); sources (microbes) anduses of organic acids, alcohols and enzymes(lipase, pectinase, protease, streptokinase)in industry, sources (microbes) andapplications of Cyclosporin-A, Statins.(iii)Sewage treatment – primary andsecondary treatment; (iv) Production ofbiogas (methanogens, biogas plant,composition of biogas and process ofproduction); (v)Biocontrol agents (ladybird,dragonfly, Bacillus thuringiensisTrichoderma, Nucleopolyhedrovirus(Baculovirus), and (vi) Microbes as biofertilisers (Rhizobium, Azospirillum, Azotobacter, Glomus, Mycorrhiza, Cyanobacteria), IPM, harmful effects of chemical pesticides.
4. Biotechnology and its Applications
(i) Biotechnology - Principles and processes
Genetic Engineering (recombinant DNAtechnology).
Definition and principles of biotechnology;isolation of genomic (chromosomal) DNA(from bacteria/plant cell/animal cell, by celllysis), isolation of gene of interest (byelectrophoresis), steps of formation ofrecombinant DNA, discovery, nomenclature,features and role of restriction enzymes(EcoRI, HindII) and role of ligase; cloningvectors (features of a good cloning vector,examples of cloning vectors like pBR322,Agrobacterium, retroviruses, bacterialartificial chromosome (BAC), yeast artificialchromosome (YAC)), methods of transfer ofrDNA into a competent host, e.g. by direct-method (temperature shock), microinjection, gene gun, methods of selection ofrecombinants (antibiotic resistance,insertional inactivation/blue-white selection), cloning of recombinants, i.e., geneamplification (by in vivo or in vitro method -using PCR technique), bioreactor (basicfeatures and uses of stirred tank and spargedtank bioreactors), downstream processing.
(ii)Biotechnology and its applications
Applications of biotechnology in health andagriculture: human insulin and vaccineproduction, stem cell technology, genetherapy; genetically modified organisms -Bt crops; transgenic animals; biosafety issues,biopiracy and biopatents.
In agriculture: Micropropagation andsomatic hybridisation techniques forproduction of GM crops tolerant to abioticstresses (cold, drought, salt, heat); pest-resistant crops (Bt-crops, RNAi with referenceto Meloidogyne incognita); crops withenhanced nutritional value (golden rice).
In medicine: insulin, vaccine production,definition of stem cells and application of stem cell technology; gene therapy - with referenceto treatment of SCID, molecular diagnosis byPCR, ELISA (the details of the technique ofELISA are not required), and use ofDNA/RNA probes.
Transgenic animals for bioactive products like alpha-1-antitrypsin for emphysema, alpha-lactalbumin; vaccine safety testing, chemical safety testing; study of diseases.
Role of GEAC, definition and two examples of biopiracy (for example Basmati rice and turmeric), biopatent; ethical issues.
5. Ecology and Environment
(i) Organisms and Populations
Population; population interactions -population attributes - growth, birth rate anddeath rate, age distribution.
Definition of population; populationattributes: sex ratio, types of age distributionpyramids for human population; definitionof population density, natality, mortality,emigration, immigration, carrying capacity.Ways to measure population density.Calculation of natality and mortality.
Population growth: factors affectingpopulation growth and population growthmodels: exponential growth and logisticgrowth models along with equations, graphand examples of the same; life historyvariations: definition of reproductive fitnessand examples.
Population interactions – definition ofmutualism, competition (interspecific,interference, competitive release andGause’s Principle of CompetitiveExclusion), predation (adaptations inorganisms to avoid predation), parasitism(ecto-, endo-, and brood parasites), commensalism, amensalism.
(ii) Ecosystem
Ecosystems: patterns, components;productivity and decomposition; energyflow; pyramids of number, biomass, energy.
Definition and types of ecosystems; structureof ecosystem (brief idea aboutbiotic and abiotic components).
Structure and function of pond ecosystem;ecosystem functions: (i) Productivity – grossprimary productivity (GPP), net primary productivity (NPP) and secondary productivity (ii) Decomposition (fragmentation, leaching, catabolism, humification and mineralization), factors affecting rate of decomposition (iii) Energy flow. Various types of food chains – grazing and detritus, food webs, trophic levels, ecological pyramids – energy, number and biomass.
Definition of PAR, 10% Law, standing crop and standing state.
(iii)Biodiversity and its Conservation
Concept of biodiversity; patterns ofbiodiversity; importance of biodiversity; lossof biodiversity; biodiversity conservation;hotspots, endangered organisms, extinction,Red Data Book, biosphere reserves, nationalparks, sanctuaries and Ramsar sites
Definition of biodiversity, few examples ofeach type of biodiversity - species, ecosystemand genetic. Global biodiversity andproportionate number of species of major taxaof plants, invertebrates and vertebrates;patterns of biodiversity (latitudinal gradients,species-area relationship – graph andequation), “rivet popper hypothesis”,importance of species diversity to theecosystem (narrowly utilitarian, broadlyutilitarian, ethical terms).
Examples of some recently extinct organisms(dodo, quagga, Steller’s Sea cow, thylacineand the three sub-species of tiger – Bali,Caspian and Javan), causes of loss ofbiodiversity (habitat loss and fragmentation,over-exploitation, alien species invasion, co-extinction).
Biodiversity conservation: In-situ methods -protected areas: biosphere reserves, nationalparks, wildlife sanctuaries, sacred groves; ex-situ methods - captive breeding, zoo,botanical gardens, cryopreservation, wild lifesafari, seed banks, tissue culture. Definitionsand examples of each of the above. Hotspots,Ramsar sites and Red Data Book.
The place, year and main agenda of historicconventions on biological diversity (the EarthSummit and the World Summit).
Note: Topics having numerical problems tobe taught with illustrative examples.
