Last Updated: April 2026
CUET 2027 | BIOLOGY
Subject Code 302 | 75 Questions | 45 to Attempt | 60 Minutes | NCERT Class 11 & 12
CUET Biology (Subject Code 302) is the gateway subject for students seeking admission to B.Sc. Biology, Biotechnology, Microbiology, and allied science programmes at top central universities. The syllabus is entirely based on NCERT Class 11 and 12 Biology textbooks. With 16 units across two classes, Biology is one of the most content-rich CUET subjects — but with the right chapter-wise approach, scoring 40+ out of 45 is achievable.
| Parameter | Details |
|---|---|
| Subject Code | 302 |
| Total Questions | 75 |
| Questions to Attempt | 45 |
| Duration | 60 minutes |
| Marking Scheme | +5 correct, -1 incorrect |
| Maximum Marks | 225 |
| NCERT Books | Biology Part 1 & 2 (Class 11 + 12) |
Chapter-wise Weightage Analysis: CUET Biology
NCERT Class 11 Biology
| Unit / Chapter | Avg. Questions | Importance |
|---|---|---|
| Unit 1: Diversity in the Living World (Kingdom Classification, Viruses, Bacteria) | 3-4 | H |
| Unit 2: Structural Organisation in Plants and Animals | 2-3 | H |
| Unit 3: Cell — Structure and Function (Cell Theory, Organelles, Cell Division) | 4-5 | H |
| Unit 4: Plant Physiology (Transport, Mineral Nutrition, Photosynthesis, Respiration, Growth) | 4-5 | H |
| Unit 5: Human Physiology (Digestion, Breathing, Body Fluids, Circulation, Excretion, Locomotion, Neural, Chemical Coordination) | 5-7 | ★ HIGHEST |
NCERT Class 12 Biology
| Unit / Chapter | Avg. Questions | Importance |
|---|---|---|
| Unit 6: Reproduction (Flowering plants + Human reproduction) | 3-5 | H |
| Unit 7: Genetics and Evolution (Mendelian Genetics, Molecular Basis, Evolution) | 5-7 | ★ HIGHEST |
| Unit 8: Biology in Human Welfare (Health, Immunity, Drugs, Microbes) | 3-4 | H |
| Unit 9: Biotechnology (Principles + Applications) | 3-4 | H |
| Unit 10: Ecology (Organisms & Populations, Ecosystem, Biodiversity, Environmental Issues) | 4-6 | ★ HIGHEST |
Unit 3: Cell — Structure and Function (Deep Dive)
Cell Theory and Cell Types
- Cell theory proposed by Schleiden (1838) and Schwann (1839); Virchow added “Omnis cellula e cellula”
- Prokaryotic cells: No membrane-bound nucleus (bacteria, archaea, cyanobacteria); 70S ribosomes
- Eukaryotic cells: Membrane-bound nucleus; 80S ribosomes in cytoplasm (70S in mitochondria/chloroplast)
Cell Organelles — High-Yield Facts
| Organelle | Key Function | CUET Exam Fact |
|---|---|---|
| Mitochondria | ATP production (aerobic respiration) | Has own DNA; called “powerhouse of cell” |
| Chloroplast | Photosynthesis | Has own DNA; thylakoid + stroma; found in plant cells |
| Ribosome | Protein synthesis | 70S in prokaryotes; 80S in eukaryote cytoplasm |
| Golgi Apparatus | Processing and packaging of proteins | “Post office of cell”; forms lysosomes |
| Lysosomes | Intracellular digestion | “Suicidal bags”; contain hydrolytic enzymes |
| ER (Rough) | Protein synthesis + transport | Has ribosomes attached on surface |
| ER (Smooth) | Lipid synthesis; detoxification | No ribosomes; abundant in liver cells |
| Centrosome | Cell division (spindle formation) | Absent in higher plant cells; present in animal cells |
Cell Division: Mitosis vs Meiosis
| Feature | Mitosis | Meiosis |
|---|---|---|
| Occurs in | Somatic (body) cells | Reproductive cells (gonads) |
| Number of divisions | 1 | 2 (Meiosis I + Meiosis II) |
| Daughter cells produced | 2 | 4 |
| Chromosome number | Maintained (2n → 2n) | Halved (2n → n) |
| Genetic variation | No (genetically identical) | Yes (crossing over in Prophase I) |
| Purpose | Growth, repair, asexual reproduction | Gamete formation (sexual reproduction) |
Unit 7: Genetics and Evolution (Highest Weightage)
Mendelian Genetics — Must-Know Laws
- Law of Segregation: Each trait is controlled by two alleles; alleles separate during gamete formation
- Law of Independent Assortment: Genes on different chromosomes are inherited independently
- Monohybrid cross ratio: 3:1 (phenotype); 1:2:1 (genotype)
- Dihybrid cross ratio: 9:3:3:1
- Incomplete dominance: F1 is intermediate (e.g., red × white = pink in snapdragon)
- Co-dominance: Both alleles expressed (ABO blood group system — I^A and I^B are co-dominant)
Molecular Basis of Inheritance — DNA Structure
- DNA double helix model: Watson and Crick (1953); based on Chargaff’s rules and Rosalind Franklin’s X-ray data
- Chargaff’s rules: A = T (connected by 2 H-bonds); G = C (connected by 3 H-bonds)
- DNA replication is semi-conservative — proven by Meselson and Stahl experiment
- Central Dogma: DNA → RNA (Transcription) → Protein (Translation)
- Reverse transcription (RNA → DNA) occurs in retroviruses (HIV); enzyme: Reverse Transcriptase
- Genetic code: 64 codons; 61 sense codons + 3 stop codons (UAA, UAG, UGA)
Evolution — Key Concepts
- Darwin’s Theory: Natural selection; survival of the fittest; variations are inherited
- Hardy-Weinberg principle: Allele frequencies remain constant in absence of evolutionary forces
- Evidences of evolution: Homologous organs (common ancestry), Analogous organs (convergent evolution), Fossils, Embryology
- Human evolution: Dryopithecus → Ramapithecus → Australopithecus → Homo habilis → Homo erectus → Homo sapiens neanderthalensis → Homo sapiens sapiens
Unit 10: Ecology — Second Highest Weightage
Ecosystem Structure and Function
- Producers (Autotrophs) → Primary Consumers → Secondary Consumers → Tertiary Consumers → Decomposers
- Energy flow: Unidirectional; only 10% energy transferred to next trophic level (10% law — Lindemann)
- Ecological pyramids: Pyramid of number, biomass, and energy; pyramid of energy is always upright
- Primary productivity: GPP = NPP + Respiration
- Succession: Hydrarch (begins in water), Xerarch (begins on dry rock); ends in climax community
Biogeochemical Cycles
- Nitrogen cycle: N₂ fixation (by Rhizobium, Azotobacter) → Nitrification (NH₃ → NO₂ → NO₃) → Assimilation → Ammonification → Denitrification
- Carbon cycle: Photosynthesis removes CO₂; Respiration + Decomposition + Combustion adds CO₂
- Phosphorus cycle: Sedimentary cycle; no gaseous phase; important for ATP, DNA, cell membrane
Biodiversity and Conservation
- India is one of 17 megadiverse countries; has 4 biodiversity hotspots: Western Ghats, Eastern Himalayas, Indo-Burma, Sundaland
- In-situ conservation: National Parks, Wildlife Sanctuaries, Biosphere Reserves, Sacred Groves
- Ex-situ conservation: Zoos, Botanical gardens, Seed banks, Gene banks, Cryopreservation
- Convention on Biological Diversity (CBD) — 1992, Rio de Janeiro
- IUCN Red List categories: Extinct, Extinct in Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern
Unit 8: Biology in Human Welfare
Immunity — Key Concepts
- Innate immunity: Non-specific; present from birth; includes skin barrier, phagocytes, NK cells
- Acquired immunity: Specific; mediated by lymphocytes; has memory
- Active immunity: Generated after infection or vaccination; long-lasting
- Passive immunity: Transfer of antibodies (mother to fetus via placenta; from colostrum); short-lasting
- B lymphocytes → Antibody-mediated (humoral) immunity
- T lymphocytes → Cell-mediated immunity
- HIV infects CD4+ T helper cells → AIDS
Unit 9: Biotechnology
Tools and Techniques
- Restriction endonucleases: Cut DNA at specific sequences (palindromic); called “molecular scissors”
- PCR (Polymerase Chain Reaction): Amplify DNA segments; invented by Kary Mullis (Nobel Prize 1993)
- Gel electrophoresis: Separate DNA fragments by size; smaller fragments travel farther
- Recombinant DNA technology: Vector (plasmid/bacteriophage) used to carry foreign DNA into host
- Bt crops: cry gene from Bacillus thuringiensis inserted into crops (Bt cotton, Bt brinjal) for pest resistance
- Golden Rice: Modified to produce beta-carotene; addresses Vitamin A deficiency
- Insulin production: Human insulin gene cloned in E. coli (first GM organism for human insulin)
Frequently Tested NCERT One-Liners
- Largest cell: Ostrich egg | Largest cell in human body: Ovum | Smallest cell: Mycoplasma
- Cell wall of fungi: Chitin | Bacteria: Peptidoglycan/Murein | Plant: Cellulose
- Transpiration occurs mainly through: Stomata (90%)
- Enzyme that catalyzes CO₂ fixation in Calvin cycle: RuBisCO
- Krebs cycle occurs in: Matrix of mitochondria
- ETC (Electron Transport Chain) occurs in: Inner mitochondrial membrane
- Okazaki fragments are found on: Lagging strand during DNA replication
- AUG codon codes for: Methionine (start codon)
- Apomixis: Seed formation without fertilization
- Emasculation: Removal of anthers before they dehisce (used in hybridization)
Phase 1 — NCERT Mastery (Month 1-2): Read all NCERT chapters focusing on definitions, processes, and diagrams. CUET Biology directly quotes NCERT. Underline every definition and named process.
Phase 2 — Diagram Mastery (Month 2-3): Even though CUET is MCQ-based, understanding diagrams helps answer “identify the structure” questions. Focus on: Mitosis/Meiosis stages, DNA structure, Nitrogen cycle, Human heart (chambers), Nephron structure, Photosynthesis light reaction diagram.
Phase 3 — Chapter-wise MCQ Practice (Month 3-4): Genetics, Ecology, and Human Physiology together account for ~50% of questions. Prioritise these. Practice previous year CUET Biology papers extensively.
Negative Marking Strategy: In CUET Biology, never attempt a question you cannot narrow down to 2 options. The -1 penalty can significantly reduce your score. It is better to attempt 42-43 confident questions than 45 with guesswork.
• Genetics mnemonic: 3:1 = Monohybrid; 9:3:3:1 = Dihybrid; 1:1 = Testcross ratio
• DNA bases: Purines = Adenine + Guanine (A+G, double ring); Pyrimidines = Thymine + Cytosine (T+C, single ring)
• Energy currency: ATP = adenosine + 3 phosphate groups; 1 glucose → 36-38 ATP (aerobic); 2 ATP (anaerobic)
• Crossing over occurs in: Pachytene of Prophase I of Meiosis (not in mitosis)
• Highest biodiversity: Tropical rainforests (Amazon) and coral reefs; India hotspots = Western Ghats (most endemic species)
• Antibiotics vs Antivirals: Penicillin targets bacteria; no antibiotic works on viruses
• Enzyme specificity: Lock and key model (Fischer); Induced fit model (Koshland) — induced fit is more accepted
• Blood groups: A = I^A I^A or I^A i; B = I^B I^B or I^B i; AB = I^A I^B (universal recipient); O = ii (universal donor)
Frequently Asked Questions
What is the CUET Biology syllabus for 2027?
CUET Biology 2027 (Subject Code 302) covers all 10 units from NCERT Class 11 Biology (Units 1-5: Diversity, Structural Organisation, Cell, Plant Physiology, Human Physiology) and NCERT Class 12 Biology (Units 6-10: Reproduction, Genetics, Human Welfare, Biotechnology, Ecology). The exam has 75 questions of which 45 are to be attempted in 60 minutes.
Which chapters carry the most weight in CUET Biology?
The three highest-weightage units in CUET Biology are: (1) Genetics and Evolution (Class 12) — approximately 5-7 questions; (2) Ecology (Class 12) — approximately 4-6 questions; and (3) Human Physiology (Class 11) — approximately 5-7 questions. Together these account for nearly 40-45% of all questions.
Are diagrams important for CUET Biology since it is MCQ-based?
Yes, diagrams are important even though CUET Biology is MCQ-only. Questions often ask students to identify a structure from a described diagram, recognise a process from a stage description, or match a function to an organelle. Understanding diagrams of mitosis/meiosis, DNA replication, photosynthesis light reactions, and the nitrogen cycle helps significantly.
Is NCERT enough for CUET Biology 2027?
Yes, NCERT is sufficient for CUET Biology 2027. The exam is entirely based on NCERT Class 11 and 12 Biology textbooks. Students who have thoroughly read all chapters, understood diagrams, and memorised key one-liners and definitions from NCERT can score very well. Additional reference books are not required.
How should I approach question selection in CUET Biology?
Since you attempt 45 out of 75 questions, question selection is a critical skill. Scan all 75 questions first, mark the ones you are fully confident about, then attempt moderately confident ones. Avoid questions where you are just guessing — the -1 negative marking penalty can reduce your score significantly. Attempting 43 confident questions is better than 45 with guesswork.
Practice Quiz — 10 CUET-Style Questions
Click an option to reveal the answer and explanation.
