Biology Class 12 Syllabus (CBSE)

Biology class 12 syllabus unit by unit, with marks

Units are numbered from VI because units I to V belong to class 11 (see the class 11 biology syllabus). Reproduction and genetics together give 36 marks, more than half the paper.

Unit VI: Reproduction (16 marks)

Chapter 1: Sexual Reproduction in Flowering Plants

Flower structure; development of male and female gametophytes; pollination types, agencies and examples; outbreeding devices; pollen-pistil interaction; double fertilisation; endosperm and embryo development, seed and fruit formation; apomixis, parthenocarpy and polyembryony.

Chapter 2: Human Reproduction

Male and female reproductive systems; microscopic anatomy of testis and ovary; gametogenesis; menstrual cycle; fertilisation, embryo development up to blastocyst and implantation; pregnancy and placenta formation (elementary idea); parturition and lactation (elementary idea).

Chapter 3: Reproductive Health

Need for reproductive health and prevention of sexually transmitted diseases; birth control methods and medical termination of pregnancy; amniocentesis; infertility and assisted reproduction methods, for example in vitro fertilisation, ZIFT and GIFT, at an elementary level.

Unit VII: Genetics and Evolution (20 marks)

Chapter 4: Principles of Inheritance and Variation

Mendelian inheritance; deviations such as incomplete dominance, co-dominance, multiple alleles and blood groups, pleiotropy; polygenic inheritance; chromosome theory; sex determination in humans, birds and honey bee; linkage and crossing over; sex-linked inheritance including haemophilia and colour blindness; Mendelian disorders in humans; chromosomal disorders.

Chapter 5: Molecular Basis of Inheritance

Search for genetic material and DNA as genetic material; structure of DNA and RNA; DNA packaging and replication; central dogma; transcription, genetic code and translation; gene expression and regulation through the lac operon; Human Genome Project and its goals; DNA fingerprinting.

Chapter 6: Evolution

Origin of life; biological evolution and evidence from palaeontology, comparative anatomy, embryology and molecular data; Darwin's contribution and the modern synthetic theory; mechanism of evolution through variation, mutation, recombination and natural selection; gene flow and genetic drift; Hardy-Weinberg equilibrium; adaptive radiation; the story of human evolution.

Units VIII, IX and X: human welfare, biotechnology and ecology

Chapter 7: Human Health and Disease

Pathogens and parasites causing human diseases such as malaria, dengue, chikungunya, filariasis, ascariasis, typhoid, pneumonia, common cold, amoebiasis and ringworm; the basics of immunity and how vaccines work; cancer; HIV and AIDS; adolescence with the risks of drugs and alcohol.

Chapter 8: Microbes in Human Welfare

Microbes in food processing, industrial production, sewage treatment and energy generation; microbes as bio-control agents and biofertilisers; antibiotics and their production.

Chapters 9 and 10: Biotechnology

Principles and processes of genetic engineering (recombinant DNA technology). Applications in health and agriculture: human insulin and vaccine production, stem cell technology, gene therapy, genetically modified organisms and Bt crops, transgenic animals, biosafety issues, biopiracy and patents.

Chapters 11 to 13: Ecology

Population interactions such as mutualism, competition, predation and parasitism; population attributes like growth, birth rate, death rate and age distribution. Ecosystem patterns, components, productivity, decomposition, energy flow and pyramids of number, biomass and energy. Biodiversity, its importance and loss, conservation, hotspots, endangered organisms, extinction, Red Data Book, sacred groves, biosphere reserves, national parks, wildlife sanctuaries and Ramsar sites.

Sections of the board biology paper

The board's latest specimen papers in this subject carry 33 compulsory questions across five sections, with internal choice in some of them.

CBSE also sets a competency balance: about half the marks test knowledge and understanding, 30% test application and 20% test analysis, evaluation and creation. In practice this means diagram-based, data-based and case questions, not only definitions.

Practical work: 30 marks

Experiments listed include studying pollen germination on a slide, quadrat studies of plant population density and frequency, a temporary mount of onion root tip for mitosis and isolation of DNA from plant material. Spotting covers items such as flowers adapted to pollination, stages of gamete development, meiosis, a mammalian blastula, pedigree charts, emasculation and bagging, disease-causing organisms and homologous and analogous organs. A tidy, complete record file is the surest way to bank those 4 marks.

Order of revision based on weightage

1. Genetics first: chapters 4 and 5 hold most of the 20 marks of Unit VII and need problem practice with crosses and pedigrees.
2. Reproduction next: diagrams of the ovule, embryo sac, testis section and menstrual cycle are repeated favourites for 3 and 5 mark answers.
3. Biotechnology: learn the steps of recombinant DNA work in order, then the applications chapter becomes easy.
4. Human welfare and ecology: shorter, fact-based chapters that suit the last month of revision.

The NCERT textbook and the CBSE sample papers and marking schemes on the board's academic website are enough. Extra question banks help with practice but should never replace the textbook.