CBSE Class 12 Biology Question Paper 2025, Download PDF for All Sets

CBSE Class 12 Biology Question Paper 2025: The CBSE Class 12 biology exam is successfully held on March 25, 2025 (Tuesday). For the students who obtained the PCB stream in Class 12th standard,  Biology is one of the most scoring and crucial subjects. Doing well in the exam, will help students to boost the overall score in board exam results.

We shared the CBSE Class 12 Biology Question Paper 2025 with solutions for all sets 1, 2, and 3 on this page. If you appeared in the exam, then check the Class 12th Biology Question Paper Analysis 2025 given on this page.

CBSE Class 12 Biology Question Paper 2025

As per the date sheet, the CBSE conducts the Class 12 Biology Exam for three hours, from 10:30 a.m. to 1:30 p.m. However, the CBSE Class 12 Biology Question Paper 2025 will be provided 15 minutes beforehand, so read the exam instructions and questions correctly. After the exam, we offers the CBSE Class 12th Biology Question Paper 2025 PDF with complete solutions to help students examine their answers and evaluate their performance. Students can now examine the most important class 12th biology questions and answers on this page for last-minute preparation.

CBSE Class 12th Biology Question Paper 2025 Pattern

The Class 12 Biology exam is a total of 100 marks and is divided into two theory (70 marks) and Practical (30 marks) exams. To pass the exam, students must secure, 33% scores of total marks The CBSE Class 12th Biology question paper has five sections and 33 questions.

In the question paper, Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each; Section– C has 7 questions of 3 marks each; Section– D has 2 case-based questions of 4 marks each; and Section–E has 3 questions of 5 marks each.

CBSE Class 12 Biology Question Paper 2025 PDF Free Download

The CBSE Class 12th Biology exam is held in offline, traditionally pen-paper mode. As a result, the physical copy of the CBSE Class 12th Biology Question Paper 2025 is handed over to the students. We will share the direct link to download the CBSE Class 12 Biology Question Paper 2025 PDF for all sets in the table below.

Class 12 Biology Question Paper 2025 Analysis

After the exam was concluded, we talked to the students who appeared in the exam to know their reaction to the question paper. As per the student’s feedback, the Biology exam was easy. Many of the questions were from previous internal tests we had taken at school, so we were prepared to answer them.

Section A, which consisted of multiple-choice questions, was a solid combination of comprehension, application, and topical topics. Q5, a rarely asked question, demonstrated that this year’s paper covered every aspect of the course. Similarly, the rest of the subjective sections consisted of questions about critical thinking and close analysis. Section D, which had case-based questions, was a bit disappointing because the questions were straightforward.

CBSE Class 12 Biology Important Questions Answers 2025

Below, we have shared some most important questions and answers for class 12 biology for your last-minute preparation. Students may go through these questions and revive the concept once they find any trouble in memorizing.

1.  Signals for parturition in human female originate from
A. Fully developed foetus only
B. Both placenta as well as fully developed foetus
C. Placenta only
D. Oxytocin released from maternal pituitary

Answer: B. Both placenta as well as fully developed foetus.

2 To produce 1600 seeds, the number of meiotic divisions required will be
A. 2400
B. 2000
C. 1600
D. 1800

Answer: B. 2000

3 A sample of normal double-stranded DNA was found to have thymine
content of 27%. What will be the expected proportion of guanine in this
strand?
A. 23%
B. 32%
C. 36%
D. 73%

Answer: A. 23%

4 E. coli has 4.6 X 10 6 base pairs and completes the process of replication in 18 minutes, then the average rate of polymerization is approximately
A. 2000 bp/s
B. 4000 bp/s
C. 3000 bp/s
D. 1000 bp/s

Answer: B. 4000 bp/s
It completes replication process in 18 minutes i.e. 18x 60 seconds.
Rate of polymerization = 4.6 x 106 bp/ 18x 60 s
= 460000/108
= 4259.1bp/s or approximately 4000 bp/sec Thus, the correct option is B

5 Suresh and Rajesh have defective haemoglobin due to genetic disorders. In Suresh, the problem is qualitative as he is having incorrectly functioning globin molecules while in Rajesh the problem is quantitative as he is
having very few globin molecules. Identify the disorder they are suffering from.

Answer: C.
Suresh: Sickle Cell Anaemia – Autosomal linked Recessive trait

Rajesh: Thalassemia – Autosomal Recessive blood disorder

6 In E.coli, the lac operon gets switched on when lactose is
A. present in the medium and it binds to the repressor.
B. not present in the medium and the repressor binds to the operator.
C. not present in the medium and RNA polymerase binds to the operator.
D. Active lactose present in the medium binds to RNA polymerase.
Answer: A. present in the medium and it binds to the repressor. 
7 Which of the following features shows the mechanism of sex determination in honey-bee?
(i) An offspring formed from the union of a sperm and egg develops as a female.
(ii) Males have half the number of chromosomes than that of female.
(iii) The males are haploid having 32 chromosomes.
(iv) All workers and males are diploid having 16 chromosomes
A. (i) and (ii)
B. (ii) and (iii)
C. (i) and (iv)
D. (ii) and (iv)
Answer: A. (i) and (ii) 
8 The following diagram shows a fragment of DNA which is going to be transcribed, the upper strand with polarity 3’ to 5’ is the template strand:
3´ ATTGCC 5´
5´ TAACGG 3´
After transcription the mRNA can be represented by:
A. 5´ AUUGCC 3´
B. 5´ AUUGCC 3’
C. 5´ UAACGG 3´
D. 5´ GGCAAU 3´
Answer: C. 5´ UAACGG 3´
9 Idli – dosa dough rises due to production of which of the following gas?
A. CO
B. CO2
C. NO
D. NO2
Answer: B. CO2
10 Adaptive radiation leads to which of the following?
A. Increased competition among species
B. Decreased speciation rates
C. Limited morphological diversity among species
D. Rapid divergence of traits among populations inhabiting a given
geographical area.
Answer: D. Rapid divergence of traits among populations inhabiting a given
geographical area.
11 Eco R1 cuts the DNA between bases G and A only when the sequence
of GAATTC is present. The number of nucleotides present in the resultant
sticky ends that will be formed in each of the two strands of DNA after this
enzyme cuts the DNA will be:
Vector DNA Foreign DNA
A. 1 & 5 5 &1
B. 2 & 4 4 &2
C. 2 & 5 5 & 2
D. 3 & 4 4 & 3
Answer: A. 1& 5; 5 &1
12 During the secondary treatment of sewage, which of the following change
in the effluent occur due to flocs?
A. Reduction in BOD
B. Increase in BOD
C. Decrease in DO
D. No change in DO or BOD

Answer: A. Reduction in BOD

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