ISC Biology 2026 Answer Key: The Council for the Indian School Certificate Examinations (CISCE) conducted the ISC Biology 2026 exam on March 6, 2026, from 2 PM to 5 PM across the nation. Students who appeared can check their answers through the unofficial ISC Biology 2026 Answer Key along with the exam analysis. The key and analysis have been updated based on the subject experts' reviews and students’ feedback.
The ISC Biology 2026 examination is structured into a 70-mark theory paper and a 30-mark practical/internal assessment, totalling 100 marks. The theory paper is a 3-hour examination (preceded by 15 minutes of reading time). The ISC Biology 2026 Question Paper consists of 4 sections of MCQS/Very Short Answer Questions, Short Answer Questions, and Long Answer Questions.
ISC Biology 2026 Answer Key Unofficial LIVE
The ISC Biology 2026 Questions were of 20,14, 21, and 15 marks. Students can cross-check their answers and calculate the estimated scores through the ISC Biology 2026 Answer Key.
| Questions | Answers |
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Section A: Multiple Choice Questions (1) Zara is suffering from a cough and has bluish lips. Her mucus is mixed with blood. What is the biological name of the causative organism responsible for Zara's C condition? |
Streptococcus pneumoniae |
| (2) Observe the relation between the first two words and complete the analogy: Dengue: Aedes: Plague: | Xenopsylla Flea |
| (3) If the number of chromosomes in the cells of the calyx is 16, how many chromosomes will be formed in the endosperm after double fertilisation? | 24 |
| (4) A scientist isolates a second restriction endonuclease from the strain DC3 of Helicobacter pyogenes. What would the scientist name it using the standard naming technique of restriction enzyme? | HpyDCII |
| (5) Meenu is suffering from a genetic disorder in which phenylpyruvic acid and its lower metabolites accumulate in blood. It causes impairment of nervous tissues. Which enzyme deficiency has caused this disorder in Meenu? | Phenylalanine hydroxylase (PAH) |
| (6) There were 770 frogs in a pond. 70 of them died within a month. Calculate the death rate of the population of frogs in the pond. | 0.09 = 9% |
| (7) A farmer notices that the leaves of his cabbage plants are curling up because of heavy infestation of aphids. Suggest one eco-friendly method to control their spread in their cabbage plants. | Biological control using natural wings. Ladybugs (Ladybird beetles) or Lacewings |
| (8) In a particular plant with bilobed dithecous anther, there were 50 Pollen Mother Cells. Only 25% could develop their pollen tubes. Calculate the number of pollen grains that would proceed for fertilisation. | 50 |
| (9) Choose the components required for the proper functioning of DNA Polymerase enzyme. | (b) Only (P), (R), and (S) |
| (10) The left hind limb of a person was swollen like an elephant's limb. Which one of the following was MOST likely the cause of swelling? | (c) Blockage of Lymph Vessels |
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(11) Given below are two statements marked Assertion and Reason. Read the two statements carefully and choose the correct option: Assertion: RNAi technique is applied to plants and animals to protect them from pest infestation. Reason: This technique inhibits the expression of certain genes in pests. |
(a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion. |
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(12) Given below are two statements marked Assertion and Reason. Read the two 141 statements carefully and choose the correct option. Assertion: Individuals with Klinefelter syndrome lose their secondary sexual characters and develop gynecomastia. Reason: The presence of the XYY chromosomal pattern leads to underdeveloped testes and reduced testosterone levels in affected males. |
(C) Assertion is True and Reason is False |
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(13) In a garden pea plant, the flowers are in axial (A) position. Find out the proportion of flowers in terminal position (a), if a cross is made between two heterozygous plants. |
25% |
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(14) Name the autoimmune disorder that affects the skeletal muscles in humans. |
Myasthenia Gravis |
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(15) Answer The Following: (i) Explain the abbrevation IUI (ii) The enzyme polynucleotide phosphorylase helps the in-vitro synthesis of RNA. Name the scientist who discovered this |
(i) Intra Utrine Insemination (ii) Severo Ochora
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(16) Shama complained of severe itching in certain parts of her body where patches as shown below appeared on her skin. Write the biological name of the causative agent responsible for her condition. |
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(17) Name the chemical messenger that activates Natural Killer T-cells and macrophages |
Interferon-gamma |
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(18) Give reason for each of the following (i) Kanika was suffering from SCID and needed periodic infusion of transformed lymphocytes. (ii) In HIV infected persons, the immune system is compromised |
(i) Limited lifespan and immortal (ii) The virus directly targets, infects, and destroys CD4+ T lymphocytes (CD4 cells). |
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Section B Question 2 (i) (ii) |
(i) S2 (ii) DNA pOLYMORPHOUS
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Question 3: In a group discussion on pollination, Shubham argued that Cleistogamy was a type of Xenogamy whereas Ameena was of the opinion that it was a kind of Autogamy Whose argument is correct? Justify. |
Closed Flower |
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Question 4: The amount of energy at the fourth trophic level in the food chain given below is 4J Grass → Zebra → Crocodile → Vulture What will be the amount of energy available at the sunlight and transducer level? |
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ISC Biology 2026 Question Paper Analysis
To evaluate their overall performance, students can check the overall and section-wise difficulty level of the ISC Biology 2026 Exam. It will be based on students' feedback and subject experts' reviews.
| Particulars | Details |
| Overall Paper Difficulty Level | Moderate |
| Section A Difficulty Level | Easy |
| Section B Difficulty Level | Easy to Moderate |
| Section C Difficulty Level | Easy to Moderate |
| Section D Difficulty Level | Moderate |
It is crucial to note that the ISC Biology 2026 Answer Key will be unofficial, and students are advised to use it only for analysis purposes. Students must secure a minimum of 40% marks in the subject to pass. A minimum aggregate of 35% across all subjects is necessary to obtain the pass certificate.
Students who wish to analyse their performance of Biology exam can check the ISC 2026 Chemistry Answer Key Unofficial (OUT) and Detailed Question Paper Analysis.
Live Updates
As of now, no complaints regarding out-of-syllabus questions have been reported by students so far. The ISC Biology paper stayed strictly within the prescribed 2026 syllabus. Check the exam analysis for the difficulty level of the paper based on students and subject expert’s feedback.
Students can now check ISC Biology 2026 Answer Key now updated by the subject experts. Students can now cross-check to calculate their estimated scores.
Experts suggest that the paper was concept-based. They noted that the weightage for Genetics and Biotechnology was perfectly in line with the pattern. According to expats, it was a scoring paper for those who focused on NCERT and ISC reference books.
Ananya says,”The diagrams were easy to draw;however, the time management was the real issue for me.”
According to Ishaan, an ISC student from Bihar, Section A was the easiest part of the paper, with most MCQs being direct. The assertion-reasoning questions required a bit of extra attention. Overall, I expect to score well.
Initial reports from students from Mumbai suggest the paper was "fairly balanced." Students mentioned that the Genetics section was a bit tricky but manageable for those who practiced. Most students seem relieved that the questions were direct and from the textbook.
The ISC Biology 2026 Examination concluded just now. The final bell rang at various centres. Students will exit the centres after submitting their answer sheets. Stay tuned with answer key, exam analysis, and students initial reactions.
The warning bell rang at 1:45 PM; the exam started at 11:00 AM. This was the signal for students to begin the final verification. It is a crucial time to ensure all extra sheets are securely tied and roll numbers are correct. Students are advised by the invigilators to cross-check their details before proceeding to write further answers.
- ISC 2025 Biology Exam Analysis: Students and experts rated the paper as moderate. Section C and Section D contained several application-based tricky questions.
- ISC 2024 Biology Exam Analysis: The paper was Moderate to Tough. Section A was particularly noted as "Moderately Challenging".
Based on the analysis of previous years' papers (2024 and 2025), the expected difficulty level for the ISC Biology 2026 exam is Moderate to Difficult. Historically, the paper is well-balanced, but there has been a noticeable shift toward application-based and critical thinking questions.
Section C is the most important part of the paper and requires about 50 to 60 minutes. These questions often require detailed answers, such as a process explanation or a larger diagram. Students must ensure they don't over-explain and stick to the main points.
Section A contains MCQs and very short answers that can be finished quickly. Do not spend more than 30–40 minutes on this section to save time for the descriptive parts later. Ensure your answers are precise; for MCQs, clearly write both the option letter and the text.
The paper consists of four sections:
- Section A - 20 marks
- Section B - 14 marks
- Section C - 21 marks
- Section D - 15 marks
Section A is compulsory, while the other sections often provide internal choices for specific questions.
The writing time for the 70-mark theory paper will officially begin as the final bell rings. Students will then have exactly three hours to complete the sections from A through D. Invigilators are now signaling students to open their answer booklets and begin the first section.
The ISC Biology Question Paper is distributed 15 minutes before the writing time starts for the "cool-off" period. This period is strictly for reading and planning; no writing on the answer booklet is allowed. Students will use this time to choose between internal choices in Sections C and D.
The entry process has officially started at several centers. Invigilators are verifying admit cards and ensuring that no prohibited electronic items are brought inside. Students are being guided to their allotted seats where they will wait for the initial instructions.
Here are some of the tips to approach MCQs or very short answer type questions:
- Start with Section A immediately as it contains MCQs and very short answers.
- Do not spend more than 30 to 40 minutes on this section
- Clearly write both the option letter and the text.
- Write at least one sentence (or as recommended in the question) for very-short answer questions.
- Use a fresh page to draw the diagram.
- Diagrams should be drawn wherever specifically asked or where they can better explain a process.
- Even if not requested, a small, neat sketch for a 3-mark or 5-mark question will add value to the answer.
- A well-labeled diagram can often fetch partial marks even if the theoretical explanation is slightly weak.
- Make sure to mark the diagram properly.
- Diagrams should be neat.
Students have begun arriving at centres and can be seen doing quick revisions of diagrams. Some students can be seen checking their admit cards and other exam essentials, like stationery items. The energy is a mix of focus and nervous anticipation as the 2026 Biology theory paper approaches.