CBSE Board Class 12 Biology Answer Key 2024 and Question Papers, Download PDF All SETs

The Central Board of Secondary Education (CBSE) conducted the Class 12 Biology board exam today, March 19, 2024. The exam was conducted between 10.30 am to 1.30 pm.

Now, as the exam is over, we bring you post-exam review, paper analysis and student feedback on the difficulty level of CBSE Class 12 Biology exam 2024. Compare your answers with the CBSE Class 12 Biology Question Paper 2024 Solved PDF available on this page.

 👉 CBSE Class 12th Biology Question Paper With Answer Key Set -1 QP. Code – 57/4/1

CBSE Class 12 Biology Exam 2024 Key Highlights

Board	Central Board of Secondary Education (CBSE)
Official Website	cbse.gov.in
Class	12
Subject	Biology
Exam Date	March 19, 2024
Exam Time	10.30 AM to 1.30 PM
Exam Difficulty Level	Moderate and Lengthy

Expert Review for CBSE Class 12 Biology Exam 2024

Reactions to the paper varied among students, with some finding it challenging while others experienced relative ease.

Subject experts evaluated the paper, noting that while most questions were straightforward, a few posed moderate difficulty.
Section A, comprising MCQs and assertion-reason based questions, was deemed the most scoring and easiest portion by experts.
Section D, especially Section C involving short answer and case-based questions, posed the most difficulty, necessitating creative thinking.
Despite the mixed difficulty levels, teachers emphasized that students who diligently prepared from NCERT books and sample papers stood to score well.

CBSE Class 12 Biology Paper Analysis 2024

Section	No. of Questions and Marks	Difficulty Level
Section A	16 MCQs (1 mark each)	Easy to Moderate with 1-2 tricky questions
Section B	5 Questions (2 marks each)	Moderate
Section C	7 Questions (3 marks each)	Moderate to Tough
Section D	2 Case-based/Source-based/Passage-based/Integrated Assessment Questions (4 marks each)	Moderate
Section E	3 Long Answer Questions (5 marks each)	Moderate to Tough

CBSE Class 12 Biology Answer Key 2024 Set -1 QP. Code – 57/4/1

Section A comprises 16 multiple-choice questions out of which 4 are based on Assertion Reasoning of 1 mark each, the answers to which for QP Code are provided here in tabular format.

1. In a fertilized ovule of an angiosperm, the cells in which n, 2n and 3n conditions respectively occur are:

(A) antipodal, zygote and endosperm
(B) zygote, nucellus and endosperm.
(C) endosperm, nucellus and zygote
(D) antipodals, synergids and integuments

Ans. (A) antipodal, zygote and endosperm

2. Select the option that gives the correct identification of ovum, morula and blastocyst in a human female reproduction system as shown in the following diagram :

(A) Ovum – B, Morula – D, Blastocyst – F
(B) Ovum – A, Morula – B, Blastocyst – G
(C) Ovum – A, Morula – E, Blastocyst – G
(D) Ovum – B, Morula – D, Blastocyst – G

Ans. (B) Ovum – A, Morula – B, Blastocyst – G

3. Study the table given below :

Contraceptive/ Contraceptive Method	Mode of Action
A. The pill	I. Prevent sperm reaching cervix
B. Condom	II. Prevent implantation
C. Vasectomy	III. Inhibits ovulation
D. Copper-T	IV. Semen contains no sperm

Select the option where contraceptive/contraceptive method are correctly matched with their mode of action.

(A) A-III, B-II, C-I, D-IV
(B) A-II, B-III, C-I, D-IV
(C) A-III, B-I, C-IV, D-II
(D) A-IV, B-III, C-II, D-I

Ans. (C) A-III, B-I, C-IV, D-II 

4. Identify the category of genetic disorder depicted in the pedigree chart given below :

(A) X-Linked recessive
(B) X-Linked dominant
(C) Autosomal recessive
(D) Autosomal dominant

Ans. (A) X-Linked recessive

5. Which was the last of the 24 human chromosome to be completely sequenced ?

(A) Chromosome-1
(B) Chromosome-11
(C) Chromosome-21
(D) Chromosome – X

Ans. (D) Chromosome – X

6. Study the following diagram of Transverse Section of a young anther of an angiosperm:

Select the option where parts ‘A’, ‘B’ and ‘C’ are correctly identified.

(A) A-Connective, B-Endothecium, C-Pollen grain.
(B) A-Endothecium, B- Connective, C-Pollen grain.
(C) A-Pollen grain, B-Connective, C-Endothecium.
(D) A-Endothecium, B-Pollen grain, C-Connective.

Ans. (D) A-Endothecium, B-Pollen grain, C-Connective.

7. Turner’s syndrome in humans occurs due to

(A) Aneuploidy
(B) Euploidy
(C) Polyploidy
(D) Autosomal abnormality

Ans. (A) Aneuploidy

8. Which of the options has correct identification of ‘P’. ‘Q’ and ‘R’ in the illustration of ‘Central Dogma’ given below ?

(A) P-Replication, Q-rRNA, R-Transcription
(B) P-Translation, Q-mRNA, R- Transcription
(C) P-Replication, Q-mRNA, R-Translation
(D) P-Transcription, Q-mRNA, R-Translation

Ans. (C) P-Replication, Q-mRNA, R-Translation

9. Who proposed the mutation theory in favour of organic evolution ?

(A) Weisman
(B) Louis Pasteur
(C) Darwin
(D) Hugo de Vries

Ans. (D) Hugo de Vries

10. Study the following list of bioactive substances and their action :

Bioactive Substance	Role
A. Statin	I. Removal of oil stains
B. Cyclosporin A	II. Removal of clots from blood vessels
C. Streptokinase	III. Lowering of blood cholesterol
D. Lipase	IV. Immuno-suppressive agent

Select the option in which the bioactive substances are correctly matched with their action.

(A) A-II, B-III, C-I, D-IV
(B) A-III, B-IV, C-II, D-I
(C) A-IV, B-I, C-II, D-III
(D) A-IV, B-II, C-I, D-III

Ans. (B) A-III, B-IV, C-II, D-I

11. The ‘molecular scissors’ fall in the category of :

(A) Cleaving enzyme
(B) Endonuclease
(C) Exonuclease
(D) Restriction enzymes

Ans. (D) Restriction enzymes

12. ELISA technique is based on the principle of

(A) DNA replication
(B) antigen-antibody interaction
(C) pathogen-antigen interaction
(D) antigen-protein interaction

Ans. (B) antigen-antibody interaction

Question Nos. 13 to 16 consist of two statements Assertion (A) and Reason (R). Answer these questions selecting the appropriate option given below :

(A) Both (A) and (R) are true and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true and (R) is not the correct explanation of (A).
(C) (A) is true, but (R) is false.
(D) (A) is false, but (R) is true.

13. Assertion (A) : A given fig species can be pollinated only by its partner wasp.

Reason (R) : The wasp pollinates the fig inflorescence while searching for suitable egg laying sites.

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

14. Assertion (A) : Plasmids are autonomously replicating circular extra-chromosomal DNA.

Reason (R) : Plasmids are usually present in Eukaryotic cells.

Ans. (C) (A) is true, but (R) is false.

15. Assertion (A) : Patents are granted by government to an inventor.

Reason (R) : Patents prevents others from commercial use of an invention.

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

16. Assertion (A) : Some aquatic ecosystems have inverted biomass pyramids.

Reason (R) : More energy is required by the organisms occupying higher trophic levels.

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

Question Number	CBSE Class 12 Biology Answer Key 2024  Set -1 QP. Code – 57/4/1
1.	A
2.	B
3.	C
4.	A
5.	D
6.	D
7.	A
8.	C
9.	D
10.	B
11.	D
12.	B
13.	A
14.	C
15.	A
16.	A