Key Trends (2021-2025)
- Weightage: 70 marks theory (Unit 1: Reproduction – 16 marks, Unit 2: Genetics – 20 marks, Unit 4: Biotech – 12 marks, Unit 5: Ecology – 12 marks).
- Repeated Types: Diagram-based (flower, DNA replication), numerical (pedigree analysis), assertion-reason, case-based on health/disease.
- High Repeat Chapters: Human Reproduction, Inheritance, Molecular Basis, Human Health, Biotechnology, Ecology.
- Changes: More case-based (2023–2025), MCQs on evolution & biodiversity.
Chapter-wise PYQ Analysis
Chapter 1: Reproduction in Organisms
- Marks: 4–6 • Repeated: Asexual vs sexual reproduction, life span, pre-fertilization events.
- Most Important Questions: Explain binary fission in Amoeba. Differentiate between asexual and sexual reproduction. (Repeated 3x)
- Keywords: asexually, sexually, zygote, gametes, parthenogenesis, vegetative propagation.
Chapter 2: Sexual Reproduction in Flowering Plants
- Marks: 6–8 • Repeated: Flower structure, pollination, double fertilization.
- Most Important Questions: Draw labelled diagram of flower. Explain double fertilization. (Repeated 4x)
- Keywords: stamen, pistil, pollen tube, endosperm, apomixis, parthenocarpy.
Chapter 3: Human Reproduction
- Marks: 8–10 • Repeated: Male/female reproductive system, gametogenesis, menstrual cycle.
- Most Important Questions: Describe spermatogenesis. Draw diagram of male reproductive system. (Repeated 5x)
- Keywords: seminiferous tubules, oviduct, implantation, corpus luteum, acrosome.
Chapter 4: Reproductive Health
- Marks: 4–6 • Repeated: Contraception methods, STDs, population control.
- Most Important Questions: Explain barrier methods of contraception. What are STDs? (Repeated 3x)
- Keywords: contraception, IUD, vasectomy, tubectomy, amniocentesis, MTP.
Chapter 5: Principles of Inheritance and Variation
- Marks: 10–12 • Repeated: Mendel's laws, linkage, pedigree analysis.
- Most Important Questions: Solve monohybrid/dihybrid cross. Explain incomplete dominance. (Repeated 5x)
- Keywords: genotype, phenotype, monohybrid, dihybrid, linkage, crossing over, pedigree.
Chapter 6: Molecular Basis of Inheritance
- Marks: 10–12 • Repeated: DNA structure, replication, transcription, translation.
- Most Important Questions: Explain semi-conservative replication. Draw DNA double helix. (Repeated 6x)
- Keywords: DNA, RNA, replication, transcription, translation, codon, anticodon, lac operon.
Chapter 7: Evolution
- Marks: 6–8 • Repeated: Darwin's theory, natural selection, Hardy-Weinberg.
- Most Important Questions: Explain Lamarckism vs Darwinism. Calculate allele frequency. (Repeated 4x)
- Keywords: natural selection, adaptive radiation, Hardy-Weinberg, speciation, fossils.
Chapter 8: Human Health and Disease
- Marks: 6–8 • Repeated: Immunity, diseases, vaccines, cancer.
- Most Important Questions: Differentiate innate vs acquired immunity. Explain AIDS. (Repeated 4x)
- Keywords: immunity, vaccine, antigen, antibody, cancer, metastasis, drugs.
Chapter 9: Strategies for Enhancement in Food Production
- Marks: 4–6 • Repeated: Plant breeding, tissue culture, animal husbandry.
- Most Important Questions: Explain tissue culture techniques. What is SCID? (Repeated 3x)
- Keywords: plant breeding, biofortification, somaclonal variation, embryo rescue, SCID.
Chapter 10: Microbes in Human Welfare
- Marks: 4–6 • Repeated: Sewage treatment, biogas, antibiotics.
- Most Important Questions: Explain sewage treatment process. Role of microbes in biogas. (Repeated 3x)
- Keywords: sewage, BOD, biogas, antibiotics, statins, biofertilizers.
Chapter 11: Biotechnology: Principles and Processes
- Marks: 6–8 • Repeated: Recombinant DNA, PCR, gel electrophoresis.
- Most Important Questions: Explain recombinant DNA technology steps. What is PCR? (Repeated 5x)
- Keywords: restriction enzyme, ligase, PCR, cloning vector, plasmid, gel electrophoresis.
Chapter 12: Biotechnology and its Applications
- Marks: 6–8 • Repeated: Bt cotton, gene therapy, RNAi.
- Most Important Questions: Explain Bt cotton. What is RNAi? (Repeated 4x)
- Keywords: Bt cotton, gene therapy, RNAi, transgenic, molecular diagnostics.
Chapter 13: Organisms and Populations
- Marks: 4–6 • Repeated: Adaptations, population attributes, growth models.
- Most Important Questions: Explain exponential population growth. Adaptations in desert animals. (Repeated 3x)
- Keywords: natality, mortality, population density, exponential, logistic growth, adaptations.
Chapter 14: Ecosystem
- Marks: 6–8 • Repeated: Energy flow, nutrient cycles, succession.
- Most Important Questions: Draw energy pyramid. Explain carbon cycle. (Repeated 4x)
- Keywords: productivity, decomposition, energy flow, nutrient cycling, succession.
Chapter 15: Biodiversity and Conservation
- Marks: 4–6 • Repeated: Biodiversity levels, threats, conservation strategies.
- Most Important Questions: Explain in-situ vs ex-situ conservation. Hotspots of India. (Repeated 3x)
- Keywords: biodiversity, hotspots, endangered, in-situ, ex-situ, IUCN.
Chapter 16: Environmental Issues
- Marks: 4–6 • Repeated: Pollution types, global warming, ozone depletion.
- Most Important Questions: Explain greenhouse effect. What is biomagnification? (Repeated 3x)
- Keywords: pollution, BOD, eutrophication, greenhouse, ozone hole, biomagnification.
Exam Strategy – Biology (2026 Boards)
- High-weightage: Genetics (20 marks), Reproduction (16 marks), Biotech (12 marks), Ecology (12 marks).
- Repeated: Diagrams (flower, DNA, pedigree – 3–5 marks), case-based (health/disease – 4 marks).
- Time: 10–12 min per 5-mark question, practice 2 diagrams daily.
- Tip: Focus on NCERT lines for MCQs, draw labelled diagrams neatly.
This guide is based on CBSE PYQs 2021–2025.
Practice full papers for best results.