CBSE Class 12 Biology Sample Paper 2025 PDF with Solution -

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CBSE Class 12 Biology Sample Paper 2025

The CBSE Class 12 Biology Sample Paper 2024 is the best way to evaluate your biology subject preparation before the exam. The CBSE Board exams are expected to be conducted in February and March month like every year. So, students have ample time to complete the syllabus and to practice more and more CBSE Biology sample questions.

The Class 12 Biology Sample Paper 2025 is also a tool that introduces the students to the syllabus, and exam pattern in a more practical way. For that purpose, we have offered here a complete CBSE Biology Class 12 Sample Paper 2025 with a solution, practice it with a timer for better results.

CBSE Class 12 Biology Sample Paper 2025: Pattern

CBSE Class 12 Biology Sample Paper 2025 allows us to know the complete paper pattern. Read the highlights of the biology paper pattern below.

All questions in this Class 12 Biology sample paper are mandatory.
A total of 3 hours will be given to the students for 70 marks.
The CBSE Biology question paper consists of five sections and 33 questions. All questions are mandatory.
Section A of this practice paper contains 16 questions worth 1 mark each;
Section B contains 5 questions worth 2 marks each;
Section C contains 7 questions worth 3 marks each;
Section D of this sample paper contains two case-based questions worth 4 marks each; and
Section E contains three questions worth 5 marks each.
There is no overall choice of questions. (However, some questions have included internal choices. In such questions, a student can only choose one of the choices)
Wherever possible, students can add clean and well-labeled diagrams should be made

Biology Class 12 Sample Question Paper 2025

We have arranged the Biology Class 12 Sample Paper 2025 Questions the same as the real paper. Answer the full paper and match your answer with the solutions.

QUESTION –

SECTION A

The spermatogonia present on the inside wall of the seminiferous tubules multiply by mitotic division and increase in their number. Each spematogonium is diploid and contains 46 chromosomes. Some spermatogonia called primary spermatocytes periodically undergo meiosis. How many chromosomes are there in the primary spermatocyte?

Which of the following can be an ideal contraceptive for a female who wants to have space amongst her children?

Condom
Vasectomy
Pills
IUD

When Streptococcus pneumoniae (pneumococcus) bacteria are grown on a culture plate, why some produce smooth shiny colonies (S) while others produce rough colonies (R)?

(a) R strain bacteria have a mucous (polysaccharide) coat, while S strain does not

(b) S strain bacteria have a mucous (polysaccharide) coat, while R strain does not

(d) None of the above

About 2000 million years ago (mya) the first cellular forms of life appeared on earth. Small sized reptiles of that era still exist today. Imagine, how would be the mammals of that time?

Lizards
Shrews
Frogs
Fishes

A person is allergic to dust and pollen grains. He starts sneezing and suffers from symptoms like watery eyes, running nose and breathing problem. Which of the following type of antibody will be produced in his body?

Which of the following is also called an ‘adapter molecule’?

mRNA
rRNA
tRNA
snRNA

Which of the following is incorrect about BOD?

It measures the rate of uptake of oxygen by microorganism in a sample of water.
Greater the BOD of waste water, lesser is the pollution potential
It also measures the organic matter present in water
All of the above

An orchid growing as an epiphyte on a mango branch is an example of which of the following?

(a) Amensalism

(b) Parasitism

(d) Predation

The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution. What will be the effect on biodiversity if we move from the equator to the poles?

(a) It will increase

(b) It will remain the same

(d) None of the above

Trees occupy top layer of a forest, shrubs the second and herbs and the grasses occupy the bottom layers, this vertical distribution of different species occupying different levels is called

(a) Leaching

(b) Stratification

(c)Decomposition

(d) All of the above

Among animals which of the following make the most species-rich taxonomic group?

(a) Molluscs

(b) Insects

(d) All of the above

Tropical environments are.

(a) Less seasonal

(b) Constant

(d) All of the above

Question No. 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.

Assertion : The presence of thymine at the place of uracil confers additional stability to DNA.
Reason: Both DNA and RNA are able to mutate, but DNA being unstable, mutate at a faster rate.

Assertion: the innermost wall layer of a microsporangium is called tapetum.
Reason: It’s function is to nourish the pollen grains.

Assertion: Acquired immunity is pathogen specific.
Reason: It is characterised by memory and is non-specific type of defence. This means when our body encounters a pathogen for the first time it produces a response called primary response which is of high intensity.

Assertion: DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called repetitive DNA.
Reason: Polymorphism RNA sequence is the basis of genetic mapping of human genome as well as RNA fingerprinting.

SECTION B

Wings of birds and wings of butterflies contribute to locomotion. Explain the type of evolution such organs are a result of.

How has genetically modification in crops have enhanced their output?

Why does failure of testes to descend into scrotum produce sterility?

A person is infected with tetanus. What type of antibodies should be given to such an individual. What is such type of immunisation called?

Alexander Von Humbolt observed that within a region species richness increased with increasing explored area, but only to a certain limit. On a logarithmic scale, the relation between species richness and a wide variety of taxa is described by an equation.
Mention the equation.State the value of regression co-efficient for frugivorous birds and mammals in a tropical forest of different continents.

SECTION C

Draw a sectional view of the human ovary showing different stages of developing follicles, corpus luteum and ovulation.

What are satellite DNAs in a genome? Explain their role in DNA fingerprinting.

Alien species are very invasive and are also a threat to the indigenous species. Substantiate this statement with any two examples.

A person is suffering from chills and high fever recurring every three to four days. The symptoms are caused in which disease in humans. Name its causal organism. Why is the victim showing symptoms of high fever?

What is the difference between a malignant tumor and a benign tumor?

Cellular oncogenes are found is all the human beings. Why is that so that only some of them suffer from cancer?

OR
How are cancers detected? Mentions any two approaches of their
treatment.

In order to force bacteria to take up the plasmid, the bacterial cells must first be made ‘competent’ to take up DNA. How can be the bacterial cells made competent in biotechnology?

Name the set of positively charged basic proteins present in eukaryotes that along with DNA forms the nucleosome.

A typical nucleosome contains how many base pairs of DNA?

The packaging of chromatin at higher level requires an additional set of proteins. Name those proteins. Also name the transcriptionally active chromatin.

More sections will be updated soon

CBSE Class 12 Biology Sample Paper 2025 PDF

Students can download the full CBSE Class 12 Biology Sample paper 2024 in PDF format. The solutions of all biology questions are included in this document. they can download the CBSE class 12 practice paper with answers from the below link.

PDF LINK

Class 12 Biology Sample paper 2024 PDF with Solution

Class 12 Biology Sample Paper with Solution

Solutions –

Section A

Ans. 1 (d) A primary spermatocyte is a kind of cell that develops from spermatogonium in the mitotic cell division of spermatogenesis. It is diploid in nature. Because of mitotic cell division, they possess 46 chromosomes.

Ans. 2 (d) IUDs are ideal contraceptives for the females who want to delay pregnancy and/or space children. It is one of most widely accepted methods of contraception in India.

Ans3 (b) When Streptococcus pneumoniae (pneumococcus) bacteria are grown on a culture plate, some produce smooth shiny colonies (S) while others produce rough colonies (R). This is because the S strain bacteria have a mucous (polysaccharide) coat, while R strain does not.

Ans. 4.(b) The early mammals were like shrews.

Ans. 5. The type of antibodies produced during allergy are IgE type. IgE mediates the immediate hypersensitivity reactions and also acts as a mediator in allergic response.

Ans. 6. (c)The tRNA molecules are called as adaptor molecules because they can bind with both the amino acids as well as RNA.

Ans. 7. (b) The greater the BOD (Biochemical Oxygen Demand) of the water, the more is its polluting potential because the rapidly the oxygen is depleted in the water. This means lesser oxygen is available for higher forms of aquatic life and thus water will be disturbed.

Ans. 8 (c) Commensalism is the interaction in which one species benefits and the other is neither harmed nor benefited, e.g n orchid growing as an epiphyte on a mango branch.

S9.Ans.(c)

Sol. biodiversity is minimum in the Arctic region, moderate in a temperate area and maximum in tropical regions.

(b) the vertical distribution is called as stratification.
(b) Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. That means, out of every 10 animals on this planet, 7 are insects.
(d) Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable.
(c) the presence of thymine at the place of uracil also confers additional stability to DNA. Both DNA and RNA are able to mutate. In fact, RNA being unstable, mutate at a faster rate. Consequently, viruses having RNA genome and having shorter life span mutate and evolve faster. RNA can directly code for the synthesis of protein.
(a) In a transverse section, a typical microsporangium appears near circular in outline. It is generally surrounded by four wall layers the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum. It nourishes the developing pollen grains.
(c) Acquired immunity, on the other hand is pathogen specific. It is characterised by memory. This means when our body encounters a pathogen for the first time it produces a response called primary response which is of low intensity. It is innate immunity that is non-specific type of defence.
(c) Polymorphism in DNA sequence is the basis of genetic mapping of human genome as well as DNA fingerprinting.

Section B

Ans. 17 Birds and bats are very different from evolutionary point of view both anatomically and physiologically. Though their wings contribute to locomotion (flying) but they have a different structural plant as they have different ancestors. The organs of such type are called as analogous organs and are result of convergent evolution a process in which the organism are not related closely but have evolved similar traits due to adaptations to similar ecological niches.

Ans. 18. Genetic modification is not only restricted to organism but it has also been applied to crops for their betterment by the scientist. Genetic modification have made crops stress resistant to cold, heat and drought.

They have also become pest resistant that cuts down the use of pesticides which have made them ecologically and economically beneficial. Genetic modification has increased their mineral usage that maintains their mineral content.

Ans. 19. If the testes fail to descend in the scrotum then this causes sterility as sperm formation does not takes place at abdominal temperature. Testis descend in the scrotum because sperm formation requires lower temperature than the body.

Ans. 20. If a person is infected with some deadly microbes to which quick immune response is required just as in tetanus, preformed antibodies, or antitoxin (a preparation containing antibodies to the toxin) should be injected immediately. This type of immunisation is called passive immunisation.

Ans. 21. (a) The equation is as follows:
Log S = log C + Z log A
Where:
S is the species richness
A is the area
Z is slope of the line (regression coefficient)
C = Y- intercept

(c)The value of regression co-efficient for frugivorous birds and mammals in a tropical forest of different continents IS 1.15.