ISC Class 12 Biology Previous Year Question Papers with Solutions (2026, 2024, 2023, 2022, 2020)

Looking for the 2025 paper? CISCE's Analysis of Pupil Performance for ISC Biology 2025 reprints the full 2025 paper with the marking scheme and examiners' comments on each question. It is a free PDF on cisce.org. There is no 2021 paper, because CISCE cancelled that year's ISC board exams during COVID-19.

ISC Class 12 Biology PYQ 2026: chapter-wise marks

The 2026 paper had 18 compulsory questions for 70 marks, in the same four-section layout as 2025. We sorted every sub-part by unit:

• Reproduction (flowering plants, human reproduction and reproductive health): 16 marks
• Genetics and the molecular basis of inheritance: 15 marks
• Ecology, populations and biodiversity: 15 marks
• Human health, disease and immunity, including drugs: 13 marks
• Biotechnology and its uses: 10 marks
• One mark, on an eco-friendly way to control aphids, fits either human welfare or ecology. Evolution: no question at all.
• Layout: Section A had 20 one-mark items, only four of them MCQs (two assertion-reason). Sections B, C and D had seven 2-mark, seven 3-mark and three 5-mark questions. Each of B, C and D had one internal choice.

Source: CISCE ISC 2026 Biology Paper 1 (Theory) and ISC 2025 paper as reprinted in CISCE's Analysis of Pupil Performance, Gradehunt analysis.

Look at Section A again: 16 of its 20 marks were short written answers, not options to tick. You had to name a pathogen from symptoms, name a restriction enzyme, count chromosomes in the endosperm and work out a death rate. Spelling the scientific name right matters here.

At least 24 marks began with something to read first: a gel with DNA bands, a table of bird numbers against wetland area, island areas against species counts, the structure of a drug, a sperm diagram, locust counts to plot as a growth curve and a transcription diagram. Practise reading data before writing.

What repeats in ISC Biology papers

Put the 2025 and 2026 papers side by side and several one-mark formats come back almost unchanged: naming a restriction enzyme from its source strain, endosperm ploidy or chromosome count, a population growth or death rate sum, and a word analogy (Lipase is to Candida lipolytica in 2025, Dengue is to Aedes in 2026). These are quick marks once you know the rule behind each.

Evolution is the gap. In 2025 it carried an assertion-reason item on convergent evolution and a 3-mark Hardy-Weinberg question (Q10). In 2026 it had nothing. One paper is not a pattern, and CISCE's examiners listed Hardy-Weinberg numericals among the topics students struggled with in 2025, so keep revising it.

Where ISC Biology students lost marks in 2025

CISCE's 2025 report covers 23,202 ISC Biology candidates, with an average of 74 out of 100, a highest score of 100 and a lowest of 3. Examiners listed these as difficult:

• Population growth rate numericals, NPP calculations and the number of primary oocytes
• Endosperm ploidy, restriction enzyme naming and blue-white selection of recombinants
• Drawing and reading pedigree charts, and Hardy-Weinberg numericals
• A labelled flow chart of the HIV life cycle

They also found students mixing up logistic and exponential growth, transcription and replication, coding and non-coding DNA strands, and apomixis, polyembryony and parthenocarpy. In 2026, Q16 asked for a growth curve and its equation and Q17 was on transcription. The report's advice: draw neat, labelled diagrams, write differences as a table, and use the exact key terms in definitions.

ISC Biology 2027: what CISCE has said

• Biology Paper 1 is on the list of ISC subjects with a 2027 specimen paper and answer key, in CISCE's circular of 9 October 2026.
• The circular says apply, analyse, evaluate and create questions will carry about 50% of the marks in 2027, and the topic weightage in the syllabus will be strictly kept.
• With that weightage, more data, graph and case questions like the ones in 2026 are likely. Check the specimen's layout against 2026 before your pre-boards.

How to practise with these papers

• Write the 2026 paper first as a three-hour test, then the 2025 paper from CISCE's report.
• Use 2024 and 2023 next. The 2022 semester papers each covered part of the syllabus, so use them for chapter revision, and 2020 for extra long answers.
• Keep a one-page list of scientific names, enzymes and scientists asked so far, and test yourself on it weekly.

For the board questions from 2016 to 2026 worked out step by step and sorted chapter by chapter, get Gradehunt's ISC Class 12 10 Years Solved Papers (PYQ).

The unit list is in our ISC Class 12 Biology syllabus outline. We also have solved past papers for ISC Chemistry and ISC Physics.