CBSE Class 12 Biology Answer Key 2025, Download SET Wise Question Paper Here

Table of Contents

CBSE Class 12 Biology Answer Key 2025: The Central Board of Secondary Education has successfully conducted the CBSE Class 12th Biology Board Exam 2025 for all the Science Stream students today i.e., March 25, 2025 [Tuesday] at various allocated exam centers across the country. The exam was being conducted in a single shift i.e., from 10:30 am to 13:15 pm in traditional offline pen and paper mode. After the successful completion of the exam, students must be looking for the unofficial answer key. So this is to inform them that we have updated direct links to check and download the unofficial set-wise CBSE Class 12th Biology Answer Key 2025 with Question Paper PDFs along with the exam analysis in the article below.

CBSE Class 12 Biology Question Paper 2025 Out

The CBSE Class 12th Biology Board Exam was successfully held for a total duration of 3 hours, with an extra 15 minutes for reading the question paper and completing other formalities. The Class 12th Biology exam was for a total of 100 marks, out of which the theory paper will have 70 marks, and the remaining 30 marks will be for the practical/viva examination.

The CBSE Class 12 Biology Question paper includes multiple-choice questions, short and long-answer-type questions, with a good amount of internal choices. The question paper covers topics like Genetics, Human Physiology, Biotechnology, Ecology, and Plant Biology. It will test students’ understanding of concepts, diagrams, and practical applications of biology in real life.

CBSE Class 12 Biology Answer Key 2025 with Question Paper PDF

Our experts have prepared an unofficial answer key for the CBSE Class 12th Biology exams 2025, providing correct answers for all questions. The answer key is available in a PDF format online, so students can easily download it without needing to log in. This will help students quickly check their answers and get an idea of their scores after the exam. CBSE Class 12th Biology Answer Key provides a set of correct solutions for the questions asked in the examination, enabling students to assess their performance and identify areas for improvement.

CBSE Class 12th Biology Answer Key 2025 with Question Paper PDF
Exam Conducting Body	Central Board of Secondary Education
Name of Examination	CBSE Class 12th Board Examination 2025
Category	Question Paper
Status	Released
CBSE Class 12th Biology Exam Date 2025	March 25, 2025
Unofficial CBSE Class 12th Biology Answer Key Release Date	March 25, 2025
Mode of Answer Key Availability	Online Mode
Class 12th Biology Total Marks (Theory Exam)	70 Marks
Negative Marking	No Marks will be deducted for any wrong attempt
Official Website	https://www.cbse.nic.in/

CBSE Class 12th Answer Key with Questions

Section – A

1. Some flowers are unisexual, this property of unisexuality of flowers prevents which kind of pollination?
(A) Both Autogamy and Geitonogamy
(B) Both Geitonogamy and Xenogamy
(C) Geitonogamy but not Xenogamy
(D) Autogamy but not Geitonogamy

Answer: (A) Both Autogamy and Geitonogamy

2. Given below is the schematic representation of spermatogenesis in human males:

Choose the option that shows the correct labelling of ‘I’, ‘II’, ‘III’ and ‘IV’ in the given diagram.

(A) I – Spermatogonia, II – Spermatid, III – Sec. Spermatocyte, IV – Spermatogonia
(B) I – Spermatid, II – Spermatogonia, III – Sec. Spermatocyte, IV – Spermatozoa
(C) I – Spermatogonia, II – Sec. Spermatocyte, III – Spermatozoa, IV – Spermatid
(D) I – Spermatogonia, II – Sec. Spermatocyte, III – Spermatid, IV – Spermatozoa

Answer: (D) I – Spermatogonia, II – Sec. Spermatocyte, III – Spermatid, IV – Spermatozoa

3. Which one of the following options shows the correct evolutionary order of the plants mentioned below?

(i) Fern
(ii) Ginkgo
(iii) Zostrophyllum
(iv) Gnetales

(A) (iii), (i), (ii), (iv)
(B) (iii), (ii), (i), (iv)
(C) (ii), (i), (iii), (iv)
(D) (iv), (iii), (ii), (i)

Answer: (A) (iii), (i), (ii), (iv)

4. In molecular biology, who proposed that genetic information flows in one direction?

(A) Har Gobind Khorana
(B) Francis Crick
(C) Watson and Crick
(D) Marshall Nirenberg

Answer: (B) Francis Crick

5. Given below is a heterogeneous RNA formed during Eukaryotic transcription:

How many introns and exons respectively are present in the hnRNA?

(A) 7, 7
(B) 8, 7
(C) 8, 8
(D) 7, 8

Answer: (D) 7, 8

6. Which of the following features correctly shows the mechanism of sex-determination in honey bees?

(i) A zygote formed from the union of a sperm and an egg develops into a male.
(ii) Males have half the number of chromosomes as that of females.
(iii) The females are diploid having 32 chromosomes.
(iv) Males have a father and can produce sons.

Choose the correct option:

(A) (i) and (ii)
(B) (ii) and (iii)
(C) (i) and (iv)
(D) (ii) and (iv)

Answer: (B) (ii) and (iii)

7. Study the items of Column-I and those of Column-II:

Column-I	Column-II
(a) RNA polymerase I	(i) 18s rRNA
(b) RNA polymerase II	(ii) SnRNAs
(c) RNA polymerase III	(iii) hnRNA

Choose the option that correctly matches the items of Column-I with those of Column-II:

(A) (a) (ii), (b) (iii), (c) (i)
(B) (a) (i), (b) (iii), (c) (ii)
(C) (a) (iii), (b) (ii), (c) (i)
(D) (a) (ii), (b) (i), (c) (iii)

Answer: (B) (a) (i), (b) (iii), (c) (ii)

8. A child with blood group A has a father with blood group B and the mother with blood group AB. Choose the option that gives the correct genotypes of father, mother, and the child:

Father	Mother	Child
(A) $I A i$	$I B i$	$I A i$
(B) $I A I B$	$I A i$	$I A I A$
(C) $I B i$	$I A I B$	$I A i$
(D) $I B I B$	$I A I B$	$I A I A$

Answer: (C)

9. The decrease in the T-Lymphocytes count in human blood will finally result in

(A) decrease in antigens
(B) decrease in antibodies
(C) increase in antibodies
(D) increase in antigens

Answer: (B) decrease in antibodie

10. If Meselson and Stahl’s experiment is continued for 80 minutes (till III generation), then what would be the ratio of DNA containing N¹⁵/N¹⁵ : N¹⁵/N¹⁴: N¹⁴/N¹⁴ in the medium?

(A) 1:1:0
(B) 0:1:3
(C) 1:2:0
(D) 1:4:0

Answer: (B) 0:1:3

11. Select the correct statement from the following biotechnology procedures:

(A) The polymerase enzyme joins the gene of interest and the vector
(B) Gel electrophoresis is used for amplification of a DNA segment
(C) PCR is used for isolation and separation of the DNA segment
(D) Plasmid DNA acts as a vector to transfer the piece of DNA attached to it

Answer: (D) Plasmid DNA acts as a vector to transfer the piece of DNA attached to it

12. For commercial and industrial production of citric acid, which one of the following microbes is used?

(A) Aspergillus niger
(B) Lactobacillus spp.
(C) Clostridium butylicum
(D) Saccharomyces cerevisiae

Answer: (A) Aspergillus niger

13. Assertion (A): Corpus luteum secretes the hormone, progesterone.
Reason (R): Hormone Progesterone is essential for maintenance of the endometrium.

Answer: (A) Both (A) and (R) are true and (R) is the correct explanation of (A).

14. Assertion (A): The number of white-winged moths decreased after industrialization in England.
Reason (R): Effects of industrialization were more marked in rural areas of England.

Answer: (C) (A) is true, but (R) is false.

15. Assertion (A): Streptococcus pneumoniae and Haemophilus influenzae are responsible for causing infectious diseases in human beings.
Reason (R): A healthy person acquires the infection by inhaling the aerosols released by an infected person.

Answer: (A) Both (A) and (R) are true and (R) is the correct explanation of (A).

16. Assertion (A): Restriction endonuclease recognizes palindromic sequence in DNA and cuts them.

Reason (R): Palindromic sequence has two unique recognition sites PstI and PvuI recognized by restriction endonuclease.

Answer: (C) (A) is true, but (R) is false.

Section – B

17. Student to attempt either option (A) or (B).

(A) Comment upon the mode of pollination in Vallisneria and Zostera.

(B) Mention any four strategies adopted by flowering plants to prevent self-pollination.

Answer: (A) Pollination in Vallisneria and Zostera:

Vallisneria follows hydrophily (water pollination) where the male flowers are released into the water and float to reach the female flowers.
Zostera also exhibits hydrophily, but its pollen grains are long, ribbon-like, and carried by water currents.

(B) Four strategies to prevent self-pollination:

Dichogamy: Stigma and anther mature at different times.
Herkogamy: Structural barriers prevent pollen from landing on the same flower’s stigma.
Self-incompatibility: Genetic mechanisms prevent self-pollen from fertilizing the ovule.
Unisexuality (Dioecy): Male and female flowers are on separate plants.

CBSE Class 12th Biology Answer Key 2025 PDF Download

After the exam, students eagerly wait for the CBSE Class 12th Biology answer key to check their answers. So this is to inform them that the unofficial answer key, prepared by our subject experts, will soon be made available soon after the exam. CBSE Class 12th Biology Answer Key provides a set of correct solutions for the questions asked in the examination, enabling students to assess their performance and identify areas for improvement. This will help students estimate their scores before the official Result is released by CBSE. We will also update the direct link to download the unofficial set-wise CBSE Class 12th Biology Answer Key 2025 below.

CBSE Class 12th Biology Answer Key 2025 PDF Download Link

CBSE Class 12th Biology Answer Key 2025 Set 1 [Available soon]

CBSE Class 12th Biology Answer Key 2025 Set 2 [Available soon]

CBSE Class 12th Biology Answer Key 2025 Set 3 [Available soon]

CBSE Class 12th Biology Answer Key 2025 Set 4 [Available soon]

How to Calculate Marks Using CBSE Class 12th Biology Answer Key 2025

Download the CBSE Class 12th Biology Answer Key 2025 from the direct link that will soon be shared in the table above.
Cross-check your responses with the correct answers provided in the unofficial Class 12th Biology Answer key.
Award one mark for each correct answer. Un attempted questions receive zero marks.
Sum up the marks for all correct responses to get an idea of your expected scores.

CBSE Class 12th Biology Question Paper 2025 PDF Download

On March 18, 2025, after the successful completion of the CBSE Class 12th Biology Board exam 2025, we updated the direct link to download set-wise Biology question papers here. As the exam is successfully conducted, students can now download their CBSE Class 12th Biology Question paper 2025 PDF for sets 1, 2, and 3 by simply clicking on the direct link that has been provided here. The question paper PDF will help those who appeared in the CBSE Class 12th Biology Exam in the academic year 2024-25 for better preparation for the exam.

CBSE Class 12th Biology Question Paper 2025 PDF Download
Sets	Download Link
CBSE Class 12th Biology Question paper 2025 Set 1	Click Here
CBSE Class 12th Biology Question paper 2025 Set 2	Click Here
CBSE Class 12th Biology Question paper 2025 Set 3	Click Here

CBSE Class 12th Biology Question Paper Analysis 2025

Students found the CBSE Class 12 Biology exam (2025) easy to moderate. While a few students found some questions a bit challenging.
MCQs were the easiest part of the paper.
Section B was moderately difficult for some students.
Case-based questions were slightly tricky and needed more thinking.
The exam had a mix of direct and application-based questions.
NCERT concepts were important for answering questions correctly.
More practice with case-based and tricky questions could help students.
Solving past papers and understanding concepts deeply were suggested for better preparation.
Overall, the exam was manageable, but extra focus on Section B and tricky questions would help in scoring higher.