CBSE Class 12 Biology Answer Key 2025: The CBSE Class 12 Biology Answer Key 2025 is a valuable resource for students who have appeared for the exam and want to check their answers. The Biology paper is a crucial subject for students aiming for higher studies in science and medical fields. With the CBSE Class 12 Biology 2025 exam date scheduled for 25th March 2025, students can use the answer key to analyze their performance and estimate their scores. The CBSE Class 12 Biology Answer Key 2025 PDF Download option allows students to access the complete solution set easily.
The answer key is available for different sets, including CBSE Class 12 Biology Answer Key Set 1 2025, CBSE Class 12 Biology Answer Key Set 2 2025, and CBSE Class 12 Biology Answer Key Set 3 2025. These answer keys provide step-by-step solutions, helping students understand the marking scheme and assess their responses.
For additional practice, students can refer to the CBSE answer sheet for practice, which offers insights into the correct way to present answers according to CBSE guidelines. Along with the answer key, referring to NCERT Solutions for CBSE Class 12 Biology Syllabus can further strengthen conceptual understanding and clarify doubts. If you're looking for the official CBSE Class 12 Biology Answer Key PDF, keep an eye on reliable sources, as CBSE or subject experts may release it soon. Stay updated and verify your answers carefully to get an idea of your final score.
| Exam Name | CBSE Class 12 Biology Exam 2025 |
| Conducting Body | Central Board of Secondary Education (CBSE) |
| Exam Date | 25th March 2025 |
| Exam Mode | Offline (Pen and Paper) |
| Exam Duration | 3 Hours |
| Total Marks | 70 Marks (Theory) + 30 Marks (Practical) |
| Answer Key Availability | To be released after the exam |
| Answer Key Format | PDF (for different sets) |
| Official Website | @cbse.gov.in |
After attempting the CBSE Class 12 Biology Question Paper, students often look for the official answer key to cross-check their responses. The CBSE Class 12 Biology Answer Key provides detailed solutions for all the questions, helping students analyze their mistakes and improve their performance.
| Particulars | PDF Link |
| CBSE Class 12 Biology Answer Key 2025 PDF- Set 1 | Download Now |
| CBSE Class 12 Biology Answer Key 2025 PDF - Set 2 | Download Now |
| CBSE Class 12 Biology Answer Key 2025 PDF - Set 3 | Download Now |
Why Use the Answer Key?
Download the CBSE Class 12 Biology Answer Key PDF now and boost your exam preparation!
Preparing for CBSE Class 12 Biology exams? The CBSE Class 12 Biology Question Paper helps students understand the exam pattern, marking scheme, and important topics covered in the syllabus. By practicing previous years’ Biology question papers, students can improve their time management and boost confidence before the board exams.
| Particulars | PDF Link |
| CBSE Class 12 Biology Question Paper 2025 PDF- Set 1 | Download Now |
| CBSE Class 12 Biology Question Paper 2025 PDF - Set 2 | Download Now |
| CBSE Class 12 Biology Question Paper 2025 PDF - Set 3 | Download Now |
The answer key is a document that contains the correct answers to all the questions asked in the CBSE Class 12 Biology board exam. It helps students compare their answers and predict their marks before the official results are released.
| Section | Type of Questions | No of Questions | Total Marks |
| A | Multiple-Choice Questions (MCQs)/ Assertion-Reasoning | 16 | 1 x 16 = 16 |
| B | Short Answer Questions | 5 | 2 x 5 = 10 |
| C | Short Answer Questions | 7 | 3 x 7 = 21 |
| D | Case-based Questions | 2 | 4 x 2 = 8 |
| E | Long Answer Questions | 3 | 5 x 3 = 15 |
The CBSE Class 12 Biology expected cutoff 2025 depends on factors such as exam difficulty, past trends, and student performance. Here is an estimate based on previous years:
| Category | Expected Cutoff (Out of 70) |
| General | 40-45 marks |
| OBC | 35-40 marks |
| SC/ST | 30-35 marks |
CBSE is expected to announce the CBSE 12th Biology result 2025 in May 2025. Students can check their results on the CBSE official website using their roll number and school code.
Get here the complete answer key for CBSE Class 12th Biology Exam 2025 (SET-3)
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
Correct 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
Correct 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)
Correct 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
Correct 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
Correct 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)
Correct 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)
Correct 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) IAi | IBi | IAi |
| (B) IAIB | IAi | IAIA |
| (C) IBi | IAIB | IAi |
| (D) IBIB | IAIB | IAIA |
Correct 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
Correct Answer: (B) decrease in antibodies
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
Correct 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
Correct 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
Correct Answer: (A) Aspergillus niger
13. Assertion (A): Corpus luteum secretes the hormone, progesterone.
Reason (R): Hormone Progesterone is essential for maintenance of the endometrium.
Correct 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.
Correct 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.
Correct 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.
Correct Answer: (C) (A) is true, but (R) is false.
17. Student to attempt either option (A) or (B).
(A) Comment upon the mode of pollination in Vallisneria and Zostera.
OR
(B) Mention any four strategies adopted by flowering plants to prevent self-pollination.
Correct 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.
18. Study the given pedigree chart in which neither of the parents shows the trait, but the trait is present in both male and female children.
(a) Write about the trait, also explain the inheritance of such trait in the progeny on the basis of the given pedigree chart.
(b) Give one example of such trait in human beings.
Correct Answer:
(a) Explanation of the Trait and Inheritance:
The given pedigree chart suggests an autosomal recessive inheritance, where both parents are carriers (heterozygous) but do not express the trait.
The affected children receive one recessive allele from each parent (homozygous recessive), leading to the expression of the trait.
This follows Mendel’s law of segregation, where 25% of offspring are affected when two carrier parents mate.
(b) Example of such trait in humans:
Sickle Cell Anemia
Cystic Fibrosis
Albinism
19. Student to attempt either option (A) or (B).
(A) Describe any two situations where a medical doctor would recommend injection of a pre-formed antibodies (antitoxins) into the body of a patient.
OR
(B) The symptoms of malaria do not appear immediately after the entry of sporozoites into the human body when bitten by female Anopheles mosquito. Explain why it happens.
Correct Answer:
(A) Two situations where pre-formed antibodies (antitoxins) are recommended:
Tetanus Infection: If a person has a deep wound and is at risk of Clostridium tetani infection, tetanus antitoxin is administered to neutralize the toxins.
Snakebite: A person bitten by a venomous snake receives anti-venom, which consists of pre-formed antibodies against the snake's venom.
(B) Why malaria symptoms do not appear immediately after infection:
When a female Anopheles mosquito bites, it injects sporozoites into the bloodstream.
These sporozoites travel to the liver, where they undergo asexual multiplication (schizogony) inside liver cells.
After 5-7 days, merozoites are released into the bloodstream, invading red blood cells (RBCs).
The destruction of RBCs and release of toxins cause fever, chills, and sweating, which are the symptoms of malaria.
The difficulty level of the CBSE Class 12 Biology exam 2025 plays a big role in determining the cutoff and student scores. Based on initial reactions:
After the exam, student reactions and expert reviews help in understanding how tough the paper was. Many students also compare their answers with coaching institutes’ solutions to estimate their scores.
Key Benefits:
Download the CBSE Class 12 Biology Question Paper PDF now and start your preparation effectively!
The CBSE Class 12 Biology Answer Key 2025 helps students evaluate their performance before the official results are out. While the unofficial answer key is useful for quick checking, the official key is the most reliable. Students should also check the expected cutoff to understand their chances of scoring well. Stay updated with CBSE notifications for the latest result and evaluation updates.
The CBSE Class 12 Biology Answer Key 2025 is the official document released by the Central Board of Secondary Education (CBSE) that contains the correct answers to the Biology exam questions. It helps students compare their responses to the official answers.
The CBSE typically releases the answer key a few days after the exam has been conducted. The exact date will be announced on the CBSE official website.
The official answer key will be available on the CBSE website (www.cbse.nic.in). Additionally, unofficial answer keys may also be available on various educational platforms and websites after the exam.
After the exam, you can compare your answers with the official answer key to estimate your score. It helps you understand where you performed well and where improvements are needed.
Yes, CBSE allows students to challenge the answer key if they find discrepancies or errors. CBSE will provide detailed instructions on how to file a challenge on their website.