ISC 2025 Biology Question Paper for Class 12

About this paper

This is ISC Class 12 Biology Paper 1 (Theory), code 863A, from the 2025 board examination set by CISCE. The footer reads 1225-863A. 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 a 20-mark set of short items, including two assertion–reason questions. Later questions include a short case on the biofertiliser Navyakosh, blue-white screening of transformed colonies, a sewage-treatment diagram, and a family study of Bleeder's disease in which the boy's mother and paternal grandmother are carriers. This copy has the questions only.

Exam

ISC Class 12

Subject

Biology

Year

2025

Paper code

863A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

18

Pages

11

Answers included

No, questions only

Paper pattern

• Section A

  20 marks

  Question 1, sub-parts of one or two marks: short answers, 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

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

Questions from this paper

1. A sports person quenched his thirst with tender coconut water. Name the part of the fruit from which the liquid is derived.
2. Rachel attained puberty at fourteen and conceived for the first time at thirty. How many primary oocytes had she lost by the time of conception?
3. A pistillate flower of a tetraploid angiosperm is pollinated by pollen from a diploid plant. What is the ploidy of the endosperm in the seeds formed?
4. A forest has a GPP of 20,000 kcal/m²/year, and 40% of this energy is used in respiration. Calculate the energy available as NPP.
5. Explain biopiracy with the help of an example.
6. Rafiq could not stop bleeding after an injury. His mother and paternal grandmother were carriers of Bleeder's disease. What inheritance pattern is this, and what are the chances that his sister Farah has the disease or is a carrier?