ISC 2026 Biology Question Paper for Class 12

About this paper

This is ISC Class 12 Biology Paper 1 (Theory), code 863A, from the 2026 board examination set by CISCE. The footer reads 1226-863A. 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 DNA profiles from a crime scene, Gause's experiment with two species of Paramecium, a species–area table for islands, and a count of locusts over 35 days used to draw a growth curve. 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

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

Questions from this paper

1. Zara has a cough, bluish lips and mucus mixed with blood. What is the biological name of the organism causing her condition?
2. If the cells of the calyx have 16 chromosomes, how many chromosomes will the endosperm have after double fertilisation?
3. Meenu has a genetic disorder in which phenylpyruvic acid and its metabolites accumulate in the blood and impair nervous tissue. Which enzyme deficiency has caused it?
4. There were 770 frogs in a pond, and 70 died within a month. Calculate the death rate of the frog population.
5. In a garden pea the flowers are axial (A). What proportion of flowers will be terminal (a) in a cross between two heterozygous plants?
6. Paramecium caudatum and Paramecium aurelia grew in separate cultures. In the same medium, P. caudatum was eliminated. Identify and explain the interaction on the basis of Gause's principle.