Biology is one of the most scoring subjects in Class 12 board exams if revised properly. Students often struggle to revise the vast syllabus in a short time before exams. That’s why short notes are extremely useful.
This blog provides chapter-wise Class 12 Biology short notes, covering key definitions, concepts, diagrams ideas, and exam-oriented points. These notes are perfect for quick revision before exams.
Class 12 Biology Short Notes 2025 | Chapter-wise Biology Revision for Exams
Chapter 1: Reproduction in Organisms
- Reproduction is the biological process by which organisms produce offspring.
- Two main types:
- Asexual reproduction: Single parent, no gamete formation (Binary fission, budding, spore formation).
- Sexual reproduction: Fusion of male and female gametes.
- Advantages of sexual reproduction:
- Genetic variation
- Better adaptability
- Life span includes:
- Juvenile phase
- Reproductive phase
- Senescent phase
Exam Tip: Differences between sexual and asexual reproduction are frequently asked.
Chapter 2: Sexual Reproduction in Flowering Plants
- Flower is the reproductive organ of angiosperms.
- Male part: Stamen (Anther + Filament)
- Female part: Pistil (Stigma, Style, Ovary)
- Microsporogenesis: Formation of pollen grains.
- Megasporogenesis: Formation of ovule.
- Double fertilization is unique to flowering plants.
- Seed and fruit formation occurs after fertilization.
Important Terms: Pollination, fertilization, endosperm, embryo.
Chapter 3: Human Reproduction
- Male reproductive system: Testes, vas deferens, prostate gland.
- Female reproductive system: Ovaries, fallopian tubes, uterus.
- Menstrual cycle: 28 days on average.
- Fertilization occurs in fallopian tube.
- Pregnancy lasts about 9 months.
Exam Focus: Diagram-based questions are common.
Chapter 4: Reproductive Health
- Reproductive health refers to total well-being in all aspects of reproduction.
- Family planning methods:
- Natural methods
- Barrier methods (condoms)
- IUDs (Copper-T)
- Surgical methods
- Sexually Transmitted Diseases (STDs): AIDS, Syphilis, Gonorrhea.
- Awareness and education help in population control.
Chapter 5: Principles of Inheritance and Variation
- Based on Mendel’s experiments on pea plants.
- Law of Dominance
- Law of Segregation
- Law of Independent Assortment
- Genotype vs Phenotype
- Incomplete dominance and codominance.
- Blood group inheritance (ABO system).
Important: Punnett square problems are scoring.
Chapter 6: Molecular Basis of Inheritance
- DNA is the genetic material.
- Structure of DNA: Double helix (Watson and Crick).
- RNA types: mRNA, tRNA, rRNA.
- Central Dogma: DNA → RNA → Protein.
- Genetic code is universal and degenerate.
- Mutations cause variations.
Chapter 7: Evolution
- Evolution means gradual change in organisms.
- Evidences of evolution:
- Fossils
- Homologous organs
- Theories:
- Lamarckism
- Darwin’s theory of natural selection
- Hardy–Weinberg principle explains genetic equilibrium.
- Human evolution occurred in stages.
Chapter 8: Human Health and Disease
- Health is a state of complete physical, mental, and social well-being.
- Pathogens cause diseases.
- Types of immunity:
- Innate immunity
- Acquired immunity
- Vaccination provides artificial immunity.
- Common diseases: Malaria, Typhoid, Tuberculosis.
- Drug and alcohol abuse affect health.
Chapter 9: Strategies for Enhancement in Food Production
- Aim: Increase food production.
- Animal breeding:
- Inbreeding
- Outbreeding
- Plant breeding techniques:
- Hybridization
- Selection
- Single Cell Protein (SCP) is an alternative food source.
- Biofortification improves nutritional quality.
Chapter 10: Microbes in Human Welfare
- Microbes are used in:
- Household products (Curd, bread)
- Industrial products (Alcohol, antibiotics)
- Sewage treatment
- Biogas production uses methanogens.
- Microbes help in biological pest control.
Chapter 11: Biotechnology: Principles and Processes
- Biotechnology uses living organisms for human benefit.
- Tools:
- Restriction enzymes
- Vectors (Plasmids)
- PCR (Polymerase Chain Reaction) amplifies DNA.
- Steps:
- Isolation of DNA
- Cutting, ligation
- Transformation
Chapter 12: Biotechnology and Its Applications
- Production of insulin using recombinant DNA technology.
- Gene therapy treats genetic disorders.
- GM crops like Bt cotton.
- Ethical issues related to GM organisms.
Chapter 13: Organisms and Populations
- Ecology studies relationships between organisms and environment.
- Population attributes:
- Density
- Growth rate
- Exponential growth and logistic growth.
- Biotic interactions:
- Mutualism
- Parasitism
- Predation
- Adaptations help organisms survive.
Chapter 14: Ecosystem
- Ecosystem includes biotic and abiotic components.
- Energy flow follows 10% law.
- Food chain and food web.
- Ecological pyramids.
- Nutrient cycles: Carbon and Nitrogen cycle.
Chapter 15: Biodiversity and Conservation
- Biodiversity means variety of life forms.
- Types:
- Genetic diversity
- Species diversity
- Biodiversity hotspots are rich in endemic species.
- Conservation methods:
- In-situ conservation
- Ex-situ conservation
Chapter 16: Environmental Issues
- Pollution types:
- Air pollution
- Water pollution
- Global warming and greenhouse effect.
- Ozone layer depletion.
- Solid waste management.
- Sustainable development is the solution.
Conclusion
These Class 12 Biology short notes are designed for quick revision before exams. If you revise these points regularly, you can easily score high marks in board exams and competitive exams like NEET.
For best results, revise diagrams, practice previous year questions, and understand concepts clearly.
FAQs – Class 12 Biology Short Notes
### What are Class 12 Biology short notes?
Class 12 Biology short notes are concise and exam-oriented summaries of each chapter. These notes include important definitions, key concepts, formulas, and facts that help students revise the full syllabus quickly before board or competitive exams.
### Are these Biology short notes enough for board exam revision?
Yes, these short notes are very useful for last-minute revision. However, for best results, students should also revise NCERT diagrams, practice previous year questions, and read detailed NCERT textbook once.
### Which chapters of Class 12 Biology are most important for exams?
Important chapters include Principles of Inheritance and Variation, Molecular Basis of Inheritance, Human Reproduction, Biotechnology, Ecology, and Environmental Issues. These chapters carry higher weightage in board exams.
### Can these short notes be used for NEET preparation?
Yes, these Class 12 Biology short notes are helpful for NEET revision, especially for concept recall. NEET aspirants should combine these notes with NCERT line-by-line study and MCQ practice.
### How should I use Class 12 Biology short notes for best results?
Students should revise these notes daily, especially before exams. Make a habit of revising one or two chapters every day, focus on diagrams, keywords, and practice writing short answers to improve speed and accuracy.