Class 12 BiologyImportant Questions for Board Exams 2025-26
29
Total Questions
25
Long Answer
4
Short Answer
Reproduction in Organisms
1 questionsWhy is sexual reproduction evolutionarily advantageous over asexual reproduction?
Sexual Reproduction in Flowering Plants
2 questionsDescribe double fertilisation in angiosperms. What is its significance?
Draw a well-labelled diagram of a mature embryo sac of an angiosperm.
Human Reproduction
2 questionsDraw a diagram of the male reproductive system and label any five parts.
Describe the menstrual cycle. What are the roles of FSH and LH?
Reproductive Health
2 questionsWhat is IVF? Describe the steps involved.
What is amniocentesis? Why is it banned in India for sex determination?
Principles of Inheritance and Variation
2 questionsExplain the inheritance of ABO blood groups in humans. Why is it an example of codominance and multiple allelism?
What is crossing over? What is its significance?
Molecular Basis of Inheritance
2 questionsExplain the lac operon model of gene regulation in E. coli. Distinguish between inducible and repressible operons.
Describe the semi-conservative mode of DNA replication. Who proved it experimentally?
Evolution
2 questionsExplain Hardy-Weinberg principle. What are the forces that disturb this equilibrium?
What is industrial melanism? How does it support Darwin's theory?
Human Health and Disease
2 questionsWhat is the difference between innate and acquired immunity? Explain with examples.
How does HIV cause AIDS? Describe the stages of HIV infection.
Strategies for Enhancement in Food Production
2 questionsWhat is tissue culture? What are its advantages in plant breeding?
What is biofortification? Give two examples of biofortified crops.
Microbes in Human Welfare
2 questionsExplain the process of sewage treatment. Distinguish between primary and secondary treatment.
What are biofertilizers? Give two examples and their uses.
Biotechnology: Principles and Processes
2 questionsWhat are restriction enzymes? How do they work? Give one example.
Describe the steps involved in recombinant DNA technology.
Biotechnology and its Applications
2 questionsHow was human insulin produced using genetic engineering? Why was this important?
What is gene therapy? Explain with the example of ADA deficiency.
Organisms and Populations
2 questionsDistinguish between exponential and logistic population growth. Draw and explain the graphs.
What is the difference between predation and parasitism? Give one example of each.
Ecosystem
2 questionsExplain the 10% law of energy transfer. Why is the pyramid of energy always upright?
What is decomposition? What are the steps involved?
Biodiversity and Conservation
2 questionsWhat is biodiversity? Explain the types of biodiversity loss. What are the major causes?
Distinguish between in situ and ex situ conservation with examples.
Frequently Asked Questions
Which are the most important questions in Class 12 Biology for CBSE board exam?
All 29 questions listed here are selected based on CBSE board exam frequency and marks weightage. Prioritise long-answer (5-mark) questions first — 25 questions here — as they carry the most marks. Short-answer questions (4 here) are next. Together they cover the questions most likely to appear.
Is it enough to study only important questions for CBSE Class 12 Biology?
Practising these 29 important questions gets you to 70–75% marks. For 85%+, also read chapter summaries and attempt at least one full sample paper under timed conditions. Use these important questions as your minimum baseline, not your ceiling.
How should I write answers in CBSE Class 12 Biology board exam?
For 1-mark questions: one direct sentence — no elaboration needed. For 3-mark questions: 3 clearly numbered points, each 1–2 lines. For 5-mark questions: brief intro + 4–5 numbered points with subject-specific keywords + 1-line conclusion. CBSE examiners look for keywords in marking schemes — structure your answers around them.
How many questions come from each chapter in Class 12 Biology CBSE board exam?
CBSE doesn't publish a fixed chapter-wise distribution, but chapters with more important questions listed here have historically appeared more frequently in board papers. Focus extra time on chapters with 5 or more questions — those chapters consistently carry high marks.