Biology is one of the most important subjects for CBSE Class 12 students, especially for those preparing for NEET, medical, or life science careers. The subject carries 70 marks in theory and 30 marks in practicals. Scoring well requires concept clarity, proper revision, and structured notes.
This blog provides chapter-wise Class 12 CBSE Biology notes, covering every topic in detail. These notes are designed for quick revision before exams and will help you understand key concepts in a simple and organized way.
Class 12 CBSE Biology Notes 2025 – Complete Chapter-wise Revision Guide
Unit I – Reproduction
Chapter 1: Reproduction in Organisms
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Asexual Reproduction
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Binary fission (Amoeba, Paramecium)
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Budding (Hydra, Yeast)
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Spore formation (Fungi)
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Sexual Reproduction
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Events: Pre-fertilization, Fertilization, Post-fertilization
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Importance: Genetic variation, continuity of species
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Life Span of Organisms: Different for each species
Chapter 2: Sexual Reproduction in Flowering Plants
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Structure of Flower: Stamen, Carpel, Pollen grain, Embryo sac
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Pollination
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Self & Cross-pollination
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Agents: Wind, Water, Insects, Animals
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Double Fertilization: Fusion of one male gamete with egg and another with polar nuclei
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Post-fertilization Events
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Endosperm formation
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Embryo development
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Seed and fruit formation
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Chapter 3: Human Reproduction
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Male Reproductive System: Testis, Vas deferens, Penis
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Female Reproductive System: Ovary, Fallopian tubes, Uterus, Vagina
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Gametogenesis: Spermatogenesis & Oogenesis
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Menstrual Cycle: Follicular phase, Ovulatory phase, Luteal phase
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Fertilization: Fusion of sperm and ovum in the fallopian tube
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Embryonic Development: Morula → Blastula → Gastrula
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Placenta: Nutrient and gas exchange between mother and fetus
Chapter 4: Reproductive Health
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Problems: Overpopulation, STDs, Infertility
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Contraceptives: Natural, Barrier, Oral pills, Surgical methods
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Medical Techniques: IVF, ICSI, Amniocentesis (misuse banned)
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Awareness: Importance of sex education
Unit II – Genetics and Evolution
Chapter 5: Principles of Inheritance and Variation
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Mendel’s Experiments: Monohybrid & Dihybrid crosses
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Laws of Inheritance: Law of Dominance, Segregation, Independent Assortment
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Incomplete Dominance: Snapdragon (pink flowers)
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Codominance: Blood group (AB)
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Multiple Alleles: ABO blood system
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Sex Determination: XX-XY, ZZ-ZW, Haplodiploidy in bees
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Genetic Disorders:
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Mendelian: Sickle-cell anemia, Cystic fibrosis
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Chromosomal: Down’s syndrome, Turner’s, Klinefelter’s
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Chapter 6: Molecular Basis of Inheritance
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DNA Structure (Watson & Crick model)
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DNA Replication: Semi-conservative model (Meselson & Stahl)
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Transcription: DNA → mRNA
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Genetic Code: Triplet, Universal, Degenerate
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Translation: mRNA → Protein
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Regulation of Gene Expression: Lac operon model
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Human Genome Project: Mapping of human genes
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DNA Fingerprinting: Used in forensic science
Chapter 7: Evolution
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Origin of Life: Miller-Urey experiment
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Theories of Evolution: Lamarckism vs Darwinism
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Evidences: Fossils, Homologous & Analogous organs, Embryology
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Hardy-Weinberg Principle: p² + 2pq + q² = 1
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Types of Natural Selection: Stabilizing, Directional, Disruptive
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Human Evolution: From Australopithecus → Homo sapiens
Unit III – Biology and Human Welfare
Chapter 8: Human Health and Disease
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Pathogens & Diseases
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Bacteria: Typhoid, Pneumonia
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Viruses: Common cold, Polio, AIDS
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Protozoa: Malaria
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Immunity: Innate & Acquired
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Vaccination & Immunization
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Allergy: Hypersensitivity reaction
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Drugs & Alcohol Abuse: Effects on human health
Chapter 9: Strategies for Enhancement in Food Production
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Plant Breeding: Disease resistance, Hybridization
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Animal Husbandry: Dairy, Poultry, Fish farming
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Tissue Culture: Micropropagation, Somaclones
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Single Cell Protein: Spirulina as a protein-rich food source
Chapter 10: Microbes in Human Welfare
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In Household Products: Yeast in bread, Lactobacillus in curd
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In Industry: Alcohol (Yeast), Antibiotics (Penicillin)
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In Sewage Treatment: Methanogens
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In Biocontrol Agents: Bacillus thuringiensis, Trichoderma
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In Biofertilizers: Rhizobium, Cyanobacteria
Unit IV – Biotechnology
Chapter 11: Biotechnology – Principles and Processes
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Tools of Biotechnology: Restriction enzymes, Ligase, Vectors
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Techniques: PCR, Gel electrophoresis, DNA cloning
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Steps: Isolation, Cutting, Ligation, Insertion, Expression
Chapter 12: Biotechnology and Its Applications
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Agriculture: Bt cotton, Golden rice
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Medicine: Insulin, Gene therapy, Vaccines
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Forensics: DNA fingerprinting
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Ethical Issues: Biopiracy, GMO concerns
Unit V – Ecology
Chapter 13: Organisms and Populations
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Interactions: Mutualism, Commensalism, Predation, Parasitism
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Population Ecology: Growth models (J-shaped, S-shaped)
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Adaptations: Physiological, Behavioral, Anatomical
Chapter 14: Ecosystem
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Structure: Biotic & Abiotic components
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Pyramid of Energy, Biomass, Number
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Nutrient Cycling: Carbon, Nitrogen cycles
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Ecosystem Services: Pollination, Climate regulation
Chapter 15: Biodiversity and Conservation
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Types: Genetic, Species, Ecosystem diversity
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Hotspots of India: Himalaya, Indo-Burma, Indo-Malayan
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Conservation Methods: In-situ (National parks, Sanctuaries), Ex-situ (Zoo, Seed banks)
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Red Data Book: List of endangered species
Chapter 16: Environmental Issues
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Pollution: Air, Water, Soil, Noise
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Global Warming & Ozone Depletion
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Solid Waste Management
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Agrochemicals & Industrial Wastes
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Sustainable Development
Tips for Exam Preparation
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Revise NCERT diagrams – they carry direct questions.
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Focus on genetics, biotechnology, and ecology (high-weightage units).
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Practice previous year CBSE papers.
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Write definitions and examples clearly.
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Make flowcharts and tables for better memory.
Frequently Asked Questions (FAQs) – Class 12 CBSE Biology Notes
Q1. What is the best way to prepare Class 12 Biology for CBSE Board exams?
The best way is to study NCERT thoroughly, make short notes for revision, practice diagrams, and solve previous year question papers. Focus more on genetics, biotechnology, ecology, and human physiology as they carry high weightage.
Q2. Are NCERT notes enough for Class 12 CBSE Biology exam?
Yes, NCERT is more than enough for scoring well in CBSE exams. Most of the questions are directly based on NCERT text, diagrams, and examples. Additional reference books can be used for deeper understanding but not compulsory.
Q3. How can I memorize long biology answers quickly?
You can use mnemonics, flowcharts, and tables to simplify concepts. Writing short notes and revising repeatedly also helps in long-term memory retention.
Q4. Which chapters are most important in Class 12 Biology for board exams?
The most important chapters include:
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Principles of Inheritance and Variation
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Molecular Basis of Inheritance
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Human Reproduction
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Biotechnology and Its Applications
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Ecosystem and Biodiversity
Q5. What is the total marks distribution for Class 12 Biology CBSE Board exam?
The Biology exam carries 70 marks for theory and 30 marks for practicals. Questions are usually a mix of short answer, long answer, and diagram-based questions.
Q6. How many hours should I study Biology daily for Class 12 boards?
Ideally, 2–3 hours of focused study daily is sufficient. Increase study hours closer to exams and revise notes regularly.
Q7. How to prepare diagrams in Class 12 Biology?
Practice NCERT diagrams neatly and label them correctly. Many exam questions are based directly on diagrams, so drawing them with clarity can fetch full marks.
Q8. What are the common mistakes students make in Biology exams?
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Ignoring NCERT diagrams
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Writing vague answers without key terms
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Not revising regularly
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Poor time management during exams
Q9. Can Class 12 Biology notes help in NEET preparation too?
Yes, Class 12 CBSE Biology notes are very useful for NEET since most questions are NCERT-based. Strong CBSE preparation gives a solid foundation for NEET.
Q10. How should I revise Class 12 Biology one day before the exam?
Revise only short notes, important diagrams, definitions, and NCERT examples. Avoid reading new material at the last minute. Focus on clarity and confidence.
Conclusion
Class 12 CBSE Biology is vast but highly scoring with the right approach. These chapter-wise notes will help you quickly revise every topic before the exam. Focus on diagrams, examples, and keywords to get full marks. A structured revision plan and consistent practice will ensure success. Subscribe My Youtube channel