ISC 2026 Biology Improvement Examination Question Paper for Class 12

About this paper

This is ISC Class 12 Biology Paper 1 (Theory) from the 2026 Improvement Examination, code 863A, set by CISCE. The footer reads 1226-863A-I.E. It carries 70 marks, runs for three hours plus fifteen minutes of reading time, and has 18 compulsory questions in four sections, with an internal choice in one question each in Sections B, C and D. Section A is Question 1, twenty one-mark parts, including multiple-choice and assertion–reason items. Later questions include a colour-blindness cross, age pyramids for two countries, the lac operon in the off and on states, a PCR diagram, and a choice between isolating DNA from plant, fungus and animal tissue and RNAi in tobacco. This copy has the questions only.

Exam

ISC Class 12

Subject

Biology

Year

2026

Paper code

863A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

18

Pages

12

Answers included

No, questions only

Paper pattern

• Section A

  20 marks

  Question 1 with 20 one-mark parts, including multiple-choice and assertion–reason items

• Section B

  14 marks

  Questions 2–8, two marks each; internal choice in one question

• Section C

  21 marks

  Questions 9–15, three marks each; internal choice in one question

• Section D

  15 marks

  Questions 16–18, five marks each; internal choice in one question

Topics covered

• Organisms and populations
• Ecosystem
• Microbes in human welfare
• Principles of inheritance and variation
• Molecular basis of inheritance
• Human reproduction
• Sexual reproduction in flowering plants
• Human health and disease
• Evolution
• Biodiversity and conservation
• Biotechnology: principles and processes
• Biotechnology and its applications

Questions from this paper

1. The roots of a black walnut secrete juglone, which harms an apple tree growing nearby. Identify the type of ecological interaction.
2. A population of 100 is in Hardy–Weinberg equilibrium. If the frequency of allele G is 0.2, how many individuals are heterozygous?
3. Calculate the number of base pairs in a DNA molecule 1700 Å long.
4. At which stage does the second meiotic division of the secondary oocyte remain arrested until fertilisation?
5. Swiss cheese has large holes. How are these holes formed?
6. Mohit's father is colour-blind and his mother is a carrier. Draw a Punnett square to find the probability that his sister Mahima is colour-blind.