ISC 2025 Biology Improvement Examination Question Paper for Class 12

About this paper

This is ISC Class 12 Biology Paper 1 (Theory) from the 2025 Improvement Examination, code 863A, set by CISCE. The footer reads 1225-863A-IE. 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 question of short items, including two assertion–reason questions and a diagram of a biosphere reserve. Later questions include an ABO blood-group puzzle about an adopted child, replica plating on ampicillin and tetracycline, age pyramids for two countries, and a choice between a transcription diagram and the Watson–Crick model. 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

12

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

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

Questions from this paper

1. Name the vectorless method used to insert a gene into a human egg cell.
2. How many meiotic divisions are necessary to produce 100 zygotes?
3. Name the organism from which the Ti plasmid has been isolated.
4. How many cycles of PCR are required to obtain 130 copies of a DNA?
5. A diploid organism is heterozygous for five loci. How many types of gametes will it produce?
6. How many sperms will be produced from 50 primary spermatocytes?