CBSE Class 12 Biology Syllabus 2026-27

The CBSE Class 12 Biology syllabus 2026-27 carries subject code 044 and splits 100 marks into a 70-mark theory paper and a 30-mark practical exam. This page was checked against the official Biology curriculum document on 2026-07-13 on cbseacademic.nic.in, so every unit weight, practical mark, and paper-pattern detail below matches the current session’s PDF. The one fact most students come looking for first:

Genetics and Evolution is the heaviest unit at 20 marks, and the Environmental Issues topic sits inside the syllabus but is assessed only formatively, not in the board exam.

Course Structure: Theory Marks by Unit (Class XII Biology)

The theory paper runs for 3 hours with a maximum of 70 marks, spread across five units numbered VI through X (NCERT, p. 9). The marks split is exact:

Study-planning insight: Genetics and Evolution carries the highest weightage at 20 marks, so students should anchor their revision there first rather than treating all five units as equal. Chapters 4 (Principles of Inheritance and Variation), 5 (Molecular Basis of Inheritance), and 6 (Evolution) together carry more marks than either of the last two units combined.

Secure this unit early, and the remaining 50 marks feel lighter.

For deeper preparation support, our Class 12 Biology notes hub organises chapter-wise material, and the broader Class 12 study notes index covers all science and humanities electives. You can also return to the main notes directory for other classes and subjects.

Chapter-wise Study Material for Every Unit Above

Chapter-wise study material for every unit above:

Exam Pattern and Question Paper Design (Theory)

The 70-mark theory paper is built around three competency bands (NCERT, p. 15). The board assigns exact weightage to each band, which tells you exactly where to focus revision effort:

The question typology spans Very Short Answer (including MCQs), Assertion-Reasoning, Short Answer, Long Answer I, Long Answer II, and Source-based / Case-based / Passage-based / Integrated assessment questions. An internal choice of approximately 33% is provided across the paper (NCERT, p. 15).

Exam-pattern mapping: because 50% of the paper tests knowledge and understanding, students should first secure definitions, labelled diagrams, and direct concept recall before attempting the 20% analyse/evaluate/create questions. Build the recall base first; the case-based application questions become easier once fundamentals are strong.

The 30% application band rewards students who connect concepts to situations (worked遗传 problems, pedigree analysis, lac operon regulation) rather than just memorising definitions.

Internal Assessment: Practical Exam Breakdown (30 Marks)

The practical exam runs for 3 hours and carries 30 marks, structured across six evaluation components (NCERT, p. 12):

List of Experiments (5 core experiments)

• Prepare a temporary mount to observe pollen germination.
• Study the plant population density by quadrat method.
• Study the plant population frequency by quadrat method.
• Prepare a temporary mount of onion root tip to study mitosis.
• Isolate DNA from available plant material such as spinach, green pea seeds, papaya, or banana.

Spotting (11 items)

• Flowers adapted to pollination by different agencies (wind, insects, birds).
• Pollen germination on stigma through a permanent slide or scanning electron micrograph.
• Identification of stages of gamete development: T.S. of testis and T.S. of ovary through permanent slides (from grasshopper or mice).
• Meiosis in onion bud cell or grasshopper testis through permanent slides.
• T.S. of blastula through permanent slides (Mammalian).
• Mendelian inheritance using seeds of different colour or sizes of any plant.
• Prepared pedigree charts of any one genetic trait: rolling of tongue, blood groups, ear lobes, widow’s peak, or colour blindness.
• Controlled pollination: emasculation, tagging, and bagging.
• Common disease-causing organisms like Ascaris, Entamoeba, Plasmodium, or any fungus causing ringworm, through permanent slides, models, or virtual images. Comment on symptoms of the diseases they cause.
• Models or specimens showing symbiotic association in lichens, root nodules of leguminous plants, and the parasitic mode of nutrition shown by Cuscuta on a host.
• Flash cards or models showing examples of homologous and analogous organs.

Common mistake: students often skip practicing the quadrat method calculations, but both population density and population frequency appear as separate listed experiments (Experiments 2 and 3). Practice both calculations, since each carries marks under the minor experiment head. Density and frequency use different formulas and different data tables, so revising only one leaves a gap the other experiment will expose.

Practical Examination for Visually Impaired Students

The official curriculum document provides a separate practical assessment scheme for visually impaired students of Classes XI and XII (NCERT, p. 13). The exam duration is 2 hours with a maximum of 30 marks:

The written test is 30 minutes long and contains 15 very short answer type questions, of which a student must answer any 10. A writer may be allowed as per CBSE examination rules. Students must also maintain a practical file recording at least five of the listed experiments. The seven prescribed practicals for visually impaired Class XII students are (NCERT, p. 14):

1. Study of flowers adapted to pollination by different agencies (wind, insects).
2. Identification of T.S. of morula or blastula of frog (Model).
3. Study of Mendelian inheritance pattern using beads or seeds of different sizes and texture.
4. Preparation of pedigree charts of genetic traits such as rolling of tongue and colour blindness.
5. Study of emasculation, tagging, and bagging through an exercise on controlled pollination.
6. Identify common disease-causing organisms like Ascaris (model) and learn common symptoms of the disease they cause.
7. Comment upon the morphological adaptations of plants found in xerophytic conditions.

Apparatus for identification includes beakers, flasks, petriplates, soil from different sites (sandy, clayey, loamy), small potted plants, aluminium foil, paint brush, test tubes, starch solution, iodine, ice cubes, Bunsen burner or spirit lamp or water bath, large flowers, maize inflorescence, a model of developmental stages highlighting morula and blastula of frog, beads or seeds of different shapes and sizes, Ascaris, and Cactus or Opuntia (model).

Deleted Topics and Changes in Biology Syllabus 2026-27

The official curriculum document contains one specific note about content that is not part of the summative board exam. On page 11, the document states that the following topics are included in the syllabus but will be assessed only formatively to reinforce understanding without adding to summative assessments. The stated objective is to reduce academic stress while ensuring meaningful learning.

Schools can integrate these with existing chapters as they align well. Relevant NCERT textual material is enclosed separately for reference.

Environmental Issues (available as a part of CBSE Reading Material) covers:

• Air pollution and its control
• Water pollution and its control
• Solid Wastes
• Agro-chemicals and their effects
• Radioactive wastes
• Greenhouse effect and global warming
• Ozone depletion in the stratosphere
• Degradation by improper resource utilisation and maintenance, and deforestation

Practical implication: Environmental Issues is still part of the syllabus for discussion and formative work, but it will not appear in the 70-mark theory board paper. The study material for this topic is not in the main NCERT Biology textbook; it sits in the CBSE Reading Material Biology Class XII document.

Students should read it for conceptual awareness, particularly to support their Ecology and Environment unit (Unit X), but they do not need to board-revise it like the other 12 chapters.

The curriculum document does not list any other chapter or topic as deleted for 2026-27. A verified no further change is itself information competitors rarely publish.

Prescribed Books for Biology Class 12

The official document lists exactly four prescribed resources for the session (NCERT, p. 14). These are the only resources endorsed by CBSE for this subject:

1. Biology, Class-XII, Published by NCERT.
2. Other related books and manuals brought out by NCERT (includes multimedia).
3. Biology Supplementary Material (Revised), available on the CBSE website.
4. Reading Material Biology Class XII — this is where the Environmental Issues topic sits, which ties back to the changes section above.

Students should confirm they are using the current NCERT edition and the revised supplementary material, as older editions may not match the updated competency-aligned curriculum.

Frequently Asked Questions

What is the total marks for CBSE Class 12 Biology theory exam 2026-27?

The theory exam carries 70 marks, conducted over 3 hours. The five theory units (VI through X) together account for these 70 marks.

How many marks are allotted to the Biology practical exam in Class 12?

The practical exam carries 30 marks and runs for 3 hours. It is split across a major experiment (5 marks), a minor experiment (4 marks), slide preparation (5 marks), spotting (7 marks), practical record and viva (4 marks), and an investigatory project with viva (5 marks).

Which unit carries the highest marks in Class 12 Biology syllabus 2026-27?

Genetics and Evolution (Unit VII) carries the highest weightage at 20 marks, covering Principles of Inheritance and Variation, Molecular Basis of Inheritance, and Evolution.

Is Environmental Issues included in the Class 12 Biology board exam 2026-27?

No. The official curriculum states that Environmental Issues is included in the syllabus but will be assessed only formatively, not in the summative board exam. The material is available separately as CBSE Reading Material.

What is the internal choice percentage in the CBSE Class 12 Biology question paper?

An internal choice of approximately 33% is provided across the question paper, as stated in the official question paper design on page 15 of the curriculum document.

How is the Biology practical exam conducted for visually impaired students?

Visually impaired students take a 2-hour practical exam of 30 marks with a separate evaluation scheme: identification and familiarity with apparatus (5 marks), a written test of 15 very short questions where 10 must be answered (10 marks), practical records (5 marks), and viva (10 marks). The written test itself lasts 30 minutes, and a writer may be allowed as per CBSE rules.

Reference: CBSE Class 12 Biology curriculum document, session 2026-27 as stated on cbseacademic.nic.in.