ISC Class 12 Biology Syllabus 2026-27

ISC Class 12 Biology is one of the most detailed and application-heavy subjects in the Science stream. The syllabus is prescribed by the Council for the Indian School Certificate Examinations (CISCE) and covers five major units spanning Reproduction, Genetics and Evolution, Human Welfare, Biotechnology, and Ecology.

A strong grasp of this syllabus is essential for the ISC board examination and for competitive entrance tests like NEET, AIIMS, JIPMER, and CUET. All structures, both internal and external, must be studied with labelled diagrams as stated in the official CISCE guidelines.

Exam Structure and Marks Distribution

All structures (internal and external) must be taught and studied along with diagrams as per the official CISCE requirement.

Unit-Wise Marks Weightage (Theory - 70 Marks)

Unit 1: Reproduction (16 Marks)

Reproduction carries the highest single-unit weightage of 16 marks. It is divided into three sub-units covering plant reproduction, human reproduction, and reproductive health.

(i) Sexual Reproduction in Flowering Plants

Covers the complete reproductive process in angiosperms from flower structure to seed and fruit formation. Key topics include:

•        Structure of microsporangium and T.S. of anther, microsporogenesis, pollen grain structure and viability

•        Pistil structure: megasporangium (L.S. of anatropous ovule), megasporogenesis, female gametophyte development

•        Types of pollination: autogamy, chasmogamy, cleistogamy, geitonogamy, xenogamy with flower adaptations for wind, water, and insect pollination

•        Pollen-pistil interaction, artificial hybridisation (emasculation and bagging), and its significance in plant breeding

•        Double fertilisation: syngamy and triple fusion, significance of double fertilisation

•        Post-fertilisation events: seed and fruit formation, embryo development in monocot and dicot; types of endosperm (cellular, nuclear, helobial)

•        Special modes: apomixis, parthenocarpy, polyembryony with brief explanations and examples

•        Fruit types: true and false fruits, L.S. of mango and coconut; internal structure of bean and maize seeds

Diagrams required: microsporangium, anatropous ovule, T.S. of anther, L.S. of mango/coconut, dicot (bean) and monocot (maize) seeds.

(ii) Human Reproduction

Covers the male and female reproductive systems, gametogenesis, fertilisation, and embryonic development.

•        Male and female reproductive organs and their functions; internal structure of testis and ovary with diagrams

•        Spermatogenesis (including spermiogenesis and spermiation) and oogenesis; hormonal control; structure of sperm and mature ovum

•        Menstrual cycle: phases, hormone action, differences between oestrous and menstrual cycle, menarche and menopause

•        Fertilisation: physico-chemical events, implantation, embryonic development up to blastocyst formation

•        Embryonic development milestones: formation of heart, limbs, digits, hair, eyelashes, external genital organs with time periods - frequently tested

•        Placenta functions; parturition and lactation with hormonal control (structure and types of placenta NOT required)

Structure and types of placenta are explicitly excluded from the syllabus.

(iii) Reproductive Health

•        Definition of reproductive health; family planning and RCH programmes; role of government in population control

•        Contraceptive methods: natural, barrier, IUDs, oral pills, spermicides, implants, surgical methods with mechanism of action

•        MTP (Medical Termination of Pregnancy): definition and reasons

•        Amniocentesis: role in detecting genetic defects

•        Assisted Reproductive Technologies: IVF, IUT, ZIFT, ICSI, GIFT, AI, IUI - definition and application only

•        STDs: causes, symptoms and prevention of genital warts, genital herpes, hepatitis-B, AIDS, gonorrhoea, syphilis, chlamydiasis, trichomoniasis

Unit 2: Genetics and Evolution (15 Marks)

(i) Principles of Inheritance and Variation

•        Mendel's Principles: monohybrid and dihybrid crosses, back cross and test cross using Punnett squares; reasons for Mendel's success

•        Deviations from Mendelism: incomplete dominance (Antirrhinum), co-dominance and multiple allelism (ABO blood groups), polygenic inheritance (skin colour in humans)

•        Pleiotropy: Phenylketonuria (PKU) in humans and starch synthesis in pea seeds

•        Pedigree charts: students must be able to create and interpret pedigree charts - explicitly stated in the syllabus

•        Chromosomal theory of inheritance; sex determination in humans (XX/XY), birds (ZZ/ZW), honey bees (haplodiploidy), grasshopper (XO)

•        Sex-linked inheritance: Drosophila (body colour, eye colour) and humans (haemophilia, colour blindness)

•        Mutation: spontaneous, induced, gene mutation types (transition, transversion, frame-shift)

•        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

•        Experiments establishing DNA as genetic material: Griffith, Avery-McLeod-McCarty, Hershey-Chase

•        DNA double helix: contributions of Miescher, Watson and Crick, Wilkins, Franklin, Chargaff; differences between DNA and RNA; types of RNA

•        DNA Replication: role of DNA polymerase and ligase, Meselson-Stahl experiment, Taylor's experiment

•        Transcription: post-transcriptional processing in eukaryotes (splicing, capping, tailing); definitions of intron, exon, cistron, recon, muton

•        Genetic code: discovery and essential features; codon definition; translation in prokaryotes

•        Lac operon in E. coli: operator, promoter, structural genes, regulator gene, inducible regulation

•        Human Genome Project: goals, methodologies (EST, Sequence Annotation), salient features and applications

•        DNA fingerprinting: technique, application and ethical issues (brief discussion)

(iii) Evolution

•        Origin of life: abiogenesis vs biogenesis, Oparin-Haldane theory, protobionts and coacervates; Miller-Urey experiment

•        Evidences of evolution: morphological (homologous/analogous organs), embryological (recapitulation theory), palaeontological (fossils, geological time scale), biogeographical and molecular evidences

•        Darwinism: salient features, contribution of Malthus, examples (giraffe's neck, industrial melanism, DDT resistance, antibiotic resistance), Lederberg's replica plating experiment

•        Neo-Darwinism: gene flow, genetic drift (Founder's effect, bottle-neck effect), mutation, recombination, natural selection; Hardy-Weinberg principle and numericals

•        Human evolution: know three features of each ancestor in sequence: Dryopithecus, Ramapithecus, Australopithecus, Homo habilis, Homo erectus, Homo neanderthalensis, Cro-magnon man, Homo sapiens sapiens

Hardy-Weinberg numericals are explicitly required. Know the equation: p2 + 2pq + q2 = 1.

Unit 3: Biology and Human Welfare (14 Marks)

(i) Human Health and Diseases

•        Communicable diseases - causative agents, symptoms, prevention:

•        Viral: common cold, chikungunya, dengue

•        Bacterial: typhoid (Widal test), pneumonia, diphtheria, plague

•        Protozoal: amoebiasis, malaria (graphic outline of Plasmodium life cycle required)

•        Helmintic: ascariasis, filariasis; Fungal: ringworm

•        Immunity types: innate (physical, physiological, cellular, cytokine barriers) and acquired (active/passive, humoral/cell-mediated)

•        Antibodies: IgG, IgA, IgM, IgD, IgE with function and location in body

•        AIDS: causative agent (HIV), transmission, diagnosis (ELISA), symptoms, replication of retrovirus with diagram and prevention

•        Cancer: types of tumour, causes, diagnosis and treatment (surgery, immunotherapy, radiotherapy); loss of contact inhibition and metastasis

•        Drugs: effects and sources of opioids, cannabinoids, cocaine and barbiturates; prevention and control of addiction

Draw the diagram of HIV replication in a human cell - this is explicitly required in the syllabus.

(ii) Microbes in Human Welfare

•        Household products: Lactobacillus (curd), Saccharomyces (bread), Propionibacterium (Swiss cheese)

•        Industrial products: antibiotics (Penicillin), organic acids, alcohols, enzymes (lipase, pectinase, protease, streptokinase), Cyclosporin-A, Statins

•        Sewage treatment: primary and secondary treatment

•        Biogas production: methanogens, biogas plant, composition and process

•        Biocontrol agents: ladybird, dragonfly, Bacillus thuringiensis, Trichoderma, Nucleopolyhedrovirus

•        Biofertilisers: Rhizobium, Azospirillum, Azotobacter, Glomus, Mycorrhiza, Cyanobacteria; harmful effects of chemical pesticides

Unit 4: Biotechnology and its Applications (10 Marks)

(i) Principles and Processes

•        Isolation of genomic DNA (cell lysis) and gene of interest (electrophoresis)

•        Restriction enzymes: EcoRI and HindII specifically - features, nomenclature, and role; role of ligase

•        Cloning vectors: features of a good vector; examples: pBR322, Agrobacterium, retroviruses, BAC, YAC

•        Transfer of rDNA: direct method (temperature shock), microinjection, gene gun

•        Selection of recombinants: antibiotic resistance, insertional inactivation/blue-white selection

•        Gene amplification: PCR technique (in vitro); bioreactors (stirred tank and sparged tank); downstream processing

(ii) Applications of Biotechnology

•        Agriculture: micropropagation, somatic hybridisation, GM crops for abiotic stress tolerance (cold, drought, salt, heat)

•        Bt crops: Cry proteins from Bacillus thuringiensis; RNAi with reference to Meloidogyne incognita

•        Nutritional enhancement: golden rice

•        Medicine: insulin production, vaccine production, stem cell technology, gene therapy for SCID, molecular diagnosis by PCR and ELISA

•        Transgenic animals: alpha-1-antitrypsin, alphalactalbumin; vaccine and chemical safety testing

•        Biosafety: role of GEAC; biopiracy examples: Basmati rice and turmeric; biopatents and ethical issues

ELISA technique details are NOT required. Only its application in diagnosis is needed.

Unit 5: Ecology and Environment (15 Marks)

(i) Organisms and Populations

•        Population attributes: sex ratio, age distribution pyramids, natality, mortality, emigration, immigration, carrying capacity

•        Population growth models: exponential growth (dN/dt = rN) and logistic growth (dN/dt = rN(K-N)/K) with equations, graphs and examples

•        Population interactions: mutualism, competition (Gause's Principle), predation, parasitism (ecto-, endo-, brood), commensalism, amensalism

(ii) Ecosystem

•        Structure: biotic and abiotic components; structure and function of pond ecosystem

•        Productivity: GPP, NPP and secondary productivity

•        Decomposition: fragmentation, leaching, catabolism, humification, mineralisation; factors affecting rate of decomposition

•        Energy flow: grazing and detritus food chains, food webs, trophic levels; 10% Law; ecological pyramids of energy, number and biomass

The energy pyramid is always upright. Know which pyramids can be inverted (number and biomass) and which cannot (energy).

(iii) Biodiversity and its Conservation

•        Types: species, ecosystem and genetic biodiversity with examples; global biodiversity and species proportions

•        Patterns: latitudinal gradients, species-area relationship (graph and equation), rivet popper hypothesis

•        Loss of biodiversity: habitat loss, over-exploitation, alien species invasion, co-extinction; recently extinct organisms: dodo, quagga, Steller's Sea cow, thylacine, three sub-species of tiger (Bali, Caspian, Javan)

•        In-situ conservation: biosphere reserves, national parks, wildlife sanctuaries, sacred groves

•        Ex-situ conservation: captive breeding, zoos, botanical gardens, cryopreservation, seed banks, tissue culture

•        Earth Summit: Rio de Janeiro, 1992; World Summit: Johannesburg, 2002

Paper II: Practical Work (15 Marks)

The practical examination is 3 hours and covers Taxonomy, Biochemical Experiments, Slide Preparation, and Spotting.

1. Taxonomy (Flower Dissection)

Students study floral characteristics through dissection and draw floral formula and diagrams for the following seven families:

•        Malvaceae (China rose/Hollyhock)

•        Leguminosae - Papilionaceae (Sweet pea/Pea/Bean)

•        Solanaceae (Petunia/Datura/Brinjal)

•        Liliaceae/Amaryllidaceae (Onion/Lily/Gladiolus)

•        Cruciferae (Mustard/Candytuft)

•        Compositae/Asteraceae (Sunflower/Marigold/Dahlia)

•        Gramineae/Poaceae (Wheat/Corn/Rice)

In the examination, candidates will be tested on any ONE of the seven families. Prepare all seven. Know scientific names and economic importance of at least two plants per family.

2. Biochemical and Physiological Experiments

•        Study of stomata distribution in dicot and monocot leaves

•        Comparative study of two soil samples: texture, moisture, humus content, water holding capacity, pH

•        Effect of amylase/diastase on starch at three temperatures (below 10 deg C, 37 deg C, above 70 deg C) and three pH values

•        Isolation of DNA from plant material (spinach, green pea, banana, papaya)

3. Slide Preparation

•        Germination of pollen grain in nutrient medium

•        T.S. of ovary to show marginal/axile placentation

•        T.S. of a hydrophyte stem

•        T.S. of a xerophytic leaf (Nerium)

•        L.S. of monocot (maize/wheat) and dicot (pea/bean) seeds

4. Spotting

Three minutes per spot: identification, labelled diagram, and two identifying characteristics.

•        T.S. of mammalian ovary and testis (chart/slide)

•        Germinating pollen grain; T.S. of ovary showing placentation type

•        T.S. of blastula/blastocyst (chart/slide)

•        Whole mount of Plasmodium sporozoite and Entamoeba histolytica trophozoite

•        Preserved specimen/chart of Ascaris

•        Ecological adaptations: Hydrilla (aquatic), cactus (xeric), fish (aquatic), camel (xeric)

•        Flowers adapted to insect, water and wind pollination with identification and two reasons

Always mention whether the specimen is a T.S., L.S., whole mount, chart, model or image as part of identification. Spotting answers are written on a separate sheet handed to the Examiner immediately after.

Project Work and Practical File (15 Marks)

Project Work carries 10 marks and Practical File carries 5 marks, both assessed by a Visiting Examiner appointed locally and approved by CISCE.

Project Work (10 Marks)

Students must complete one original investigatory project. Handwritten original projects are preferred; no plagiarism is allowed. Computer-generated projects must be submitted as a hard copy signed by the Internal Examiner and Head of Institution.

Suggested topics: Genetic disorders, Gene therapy, Human Genome Project, DNA fingerprinting, Bio-piracy, Cancer, AIDS/Hepatitis, Drug addiction, Role of microorganisms in industry, Human population, Mendelian Inheritance, Environmental resistance, Traditional vs modern pest control, Agrochemicals in food production.

Evaluation format: Introduction, Content, Presentation (graphs/tables/charts/diagrams), Conclusion/Summary, Bibliography.

Practical File (5 Marks)

Every practical must be recorded date-wise throughout the year. Each entry must be checked, signed, and dated by the teacher. The Visiting Examiner assesses the file.

Scientists and Their Key Contributions

Preparation Strategy for ISC Biology 2026-27

Unit 1 - Reproduction

•        Practise labelled diagrams of microsporangium, anatropous ovule, T.S. of anther, L.S. of mango/coconut, dicot and monocot seeds

•        Know all five types of pollination with definitions and examples

•        Double fertilisation: know both events - syngamy and triple fusion and their significance

•        Human reproduction: embryonic development milestones with time periods are frequently tested

•        All seven ART abbreviations (IVF, IUT, ZIFT, ICSI, GIFT, AI, IUI) with definition and application

Unit 2 - Genetics and Evolution

•        Practise Punnett squares for monohybrid and dihybrid crosses; learn to create and interpret pedigree charts

•        Sex determination: know all four systems - humans, birds, honey bees, grasshopper

•        Know all three DNA-proof experiments (Griffith, Avery, Hershey-Chase) with details

•        Lac operon: all components and inducible regulation mechanism

•        Human evolution: three features for each ancestor in correct sequence

•        Hardy-Weinberg: practise numericals using p2 + 2pq + q2 = 1

Unit 3 - Biology and Human Welfare

•        Life cycle of Plasmodium: graphic outline only - not the full detailed cycle

•        All four types of innate immunity and all types of acquired immunity

•        All five antibody types: IgG, IgA, IgM, IgD, IgE with function and location

•        Draw HIV replication diagram - explicitly required in the syllabus

•        Know specific organisms for each microbe application (e.g., Lactobacillus for curd, not just 'bacteria')

Unit 4 - Biotechnology

•        Know EcoRI and HindII specifically - nomenclature rules, features, and role

•        Cloning vectors: pBR322, Agrobacterium, retroviruses, BAC, YAC

•        Bt crops: Cry proteins mechanism; RNAi with reference to Meloidogyne incognita

•        Biopiracy: know the two specific examples - Basmati rice and turmeric

•        ELISA technique details NOT required - only its diagnostic application

Unit 5 - Ecology

•        Know both population growth equations and draw graphs for exponential and logistic growth

•        Energy pyramid is always upright; know which pyramids can be inverted

•        10% Law: only 10% of energy passes to the next trophic level

•        All five recently extinct organisms: dodo, quagga, Steller's Sea cow, thylacine, three tiger sub-species (Bali, Caspian, Javan)

•        Earth Summit: Rio de Janeiro 1992; World Summit: Johannesburg 2002

Frequently Asked Questions

Q1. What is the total marks structure for ISC Class 12 Biology?

Theory Paper I: 70 marks. Practical Paper II: 15 marks. Project Work: 10 marks. Practical File: 5 marks. Total: 100 marks.

Q2. Are diagrams compulsory in the theory paper?

Yes. The CISCE syllabus explicitly states: 'All structures (internal and external) are required to be taught along with diagrams.'

Q3. Is the structure and types of placenta required?

No. Structure and types of placenta are explicitly excluded from the syllabus.

Q4. Are ELISA technique details required?

No. The syllabus states ELISA technique details are not required. Only its application in diagnosis is needed.

Q5. Which family is tested in the Taxonomy practical?

Any one of the seven families - all must be prepared.

Q6. How much time is given per spot in Spotting?

Three minutes per spot, including identification, labelled diagram, and two identifying characteristics.

Q7. Are Hardy-Weinberg numericals required?

Yes. Numericals on Hardy-Weinberg equilibrium are explicitly listed in the syllabus.

Q8. Who assesses the Practical File?

The Visiting Examiner, appointed locally and approved by CISCE.

Source Reference

Based on the official CISCE ISC Biology Syllabus issued by RDCD, CISCE. Verify at cisce.org before the examination.