CBSE Class 12 Biology Answer Key 2024 with Question Paper PDF

CBSE Class 12 Biology Answer Key 2024 Set 2

Question 1 : An angiosperm embryo sac is located within the: (A) Placenta (B) Megasporangium (C) Nucellus (D) Ovary

Answer: (B) Megasporangium

Question 2 : In humans, the secondary oocyte completes meiotic division when: (A) it gets implanted in the uterine endometrium. (B) it is released from the matured Graafian follicle. (C) it is penetrated by the sperm cell. (D) acrosomal enzymes break down the zona pellucida.

Answer: (D) acrosomal enzymes break down the zona pellucida.

Question 3 : Which one of the following statements is not true? (A) Flippers of whales and dolphins are homologous organs. (B) Homologous organs have similar anatomical structure, but perform different functions. (C) Homology indicates common ancestry. (D) Homologous structures are a result of convergent evolution.

Answer: (D) Homologous structures are a result of convergent evolution.

Question 4 : A population is in genetic equilibrium/Hardy-Weinberg equilibrium for a gene with 2 alleles (dominant allele is ‘A’ and recessive allele ‘a’). If the frequency of allele ‘A’ is 0.6, then the frequency of genotype ‘Aa’ is: (A) 0.21 (B) 0.42 (C) 0.48 (D) 0.32

Answer: (C) 0.48

Question 5 : In the double helical structure of DNA molecule, the strands are: (A) identical and complementary (B) identical and non-complementary (C) anti-parallel and complementary (D) anti-parallel and non-complementary

Answer: (C) anti-parallel and complementary

Question 6 : In a ‘transcription unit’, the ‘terminator’ is located towards the: (A) 3′ end of the template strand (B) 5′ end of the template strand (C) 5′ end of the coding strand (D) 3′ end of the coding strand

Answer: (D) 3′ end of the coding strand

Question 7 : A woman with normal vision has a color-blind father. She marries a man with normal vision. The percentage chance of their progeny being color blind is: (A) 25% (B) 50% (C) 75% (D) 100%

Answer: (A) 25%

Question 8 : The vector for dengue fever is: (A) Female Aedes mosquito (B) Female Anopheles mosquito (C) Male Aedes mosquito (D) Female Culex mosquito

Answer: (A) Female Aedes mosquito

Question 9 : Which one of the following is not a feature of plasmids? (A) Circular (B) Self-replicating (C) Single stranded (D) Extra-chromosomal

Answer: (C) Single stranded

Question 10 : The pyramid of biomass in the sea is generally inverted because in the sea: (A) Biomass of fishes exceeds that of phytoplankton. (B) Number of phytoplanktons is more. (C) Number of phytoplanktons is less. (D) Large fishes feed on small fishes

Answer: (A) Biomass of fishes exceeds that of phytoplankton.

Question 11 : Which one of the following is not a feature of plasmids? (A) Single-stranded (B) Circular (C) Self-replicating (D) Extra-chromosomal

Answer: (A) Single-stranded

Question 12 : The pyramid of biomass in the sea is generally inverted because in the sea: (A) Biomass of fishes exceeds that of phytoplankton. (B) Number of phytoplanktons is more. (C) Number of phytoplanktons is less. (D) Large fishes feed on small fishes

Answer: (A) Biomass of fishes exceeds that of phytoplankton.

Assertion-Reasoning Based Questions

Question 13: Assertion (A): RNA is unstable and can mutate at a faster rate. Reason (R): The presence of 2′ OH group in every nucleotide makes it labile and easily degradable.

Answer: (a)

Question 14: Assertion (A): Virus-infected cells produce interferons. Reason (R): Interferons can cause inflammation of virus-infected cells.

Answer: (a)

Question 15: Assertion (A): Specific enzymes are used to degrade the cell wall in organisms to isolate the DNA from the cell. Reason (R): Fungal cell wall is degraded by the enzyme cellulase.

Answer: (c)

Question 16: Assertion (A): Loss of biodiversity can occur due to overexploitation of natural resources. Reason (R): Introduction of Clarias gariepinus in Indian rivers has led to a decline in native Indian fishes.

Answer: (D)

CBSE class 12 biology sample paper 2023-24

CBSE Class 12 Biology Answer Key 2024 for QP Code 57/4/3 (Set 3)

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

Answer: (A) antipodal, zygote, and endosperm

Question 2 : Turner's syndrome in humans occurs due to:

Answer: (A) Aneuploidy

Question 3 : Which of the options has the correct identification of 'P', 'Q', and 'R' in the illustration of 'Central Dogma' given below?

Answer: (D) P - Transcription, Q - mRNA, R - Translation

Question 4 : Study the following diagram of Transverse Section of a young anther of an angiosperm:

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

Question 5 : 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:

Answer: (D) Ovum - B, Morula - D, Blastocyst - G

Question 6 : Study the table given below Contraceptive/ Contraceptive Method:

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

Question 7 : Identify the category of genetic disorder depicted in the pedigree chart given below:

Answer: (A) X-Linked recessive

Question 8 : ELISA technique is based on the principle of:

Answer: (B) antigen-antibody interaction

Question 9 : Homologous organs indicate:

Answer: (B) Divergent evolution

Question 10 : The 'molecular scissors' fall in the category of:

Answer: (D) Restriction enzymes

Question 11 : Which of the chromosomes in a human possesses the least number of genes?

Answer: (D) Y-chromosome

Question 12 : Given below is a list of some commercially important products in column A, whereas in column B are names of source organisms:

Answer: (D) A - (ii), B - (iv), C - (i), D - (iii)

Question 13 : Assertion (A): Plasmids are autonomously replicating circular extra- chromosomal DNA. Reason (R): Plasmids are usually present in Eukaryotic cells.

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

Question 14 : Assertion (A): Patents are granted by the government to an inventor. Reason (R): Patents prevent others from the commercial use of an invention.

Answer: (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

Question 15 : 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.

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

Question 16 : Assertion (A): Some aquatic ecosystems have inverted biomass pyramids. Reason (R): More energy is required by the organisms occupying higher trophic levels.

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

CBSE Class 12 Biology Previous Year Question Paper

Class 12 Biology Paper Analysis 2024

The Class 12 Biology paper for the year 2024 has been analyzed as follows:

Overall Difficulty Level: Moderate Students' Feedback: Generally positive, with some finding it slightly challenging due to lengthiness Section-wise Analysis:

• Section A (MCQs): Easy to Moderate
• Section B (Short Answer Questions): Moderate
• Section C (Short Answer Questions): Moderate
• Section D (Case-based/Source-based Questions): Moderate
• Section E (Long Answer Questions): Moderate Key Highlights:
• Majority of questions were based on NCERT syllabus
• Questions were straightforward but required in-depth understanding of concepts
• Some questions were lengthy, requiring time management skills
• Overall, students found the paper manageable with adequate preparation.

CBSE Class 12 Biology Chapter-Wise Weightage 2023-24