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We bring here the latest collection of Sample Papers for Class 12 Biology prepared as per the latest examination pattern issued by CBSE. Students can refer to the latest paper below available with answers and also download the suggested guess papers in PDF format for free. Students should solve the papers in exam type environment at home and then compare their results with the answers provided below. Students should regularly solve questions given in DK Goel Class 12 book and also solve the papers given below

Sample Paper Class 12 Biology Set A

Sample Paper Class 12 Biology Set B

Sample Paper Class 12 Biology Set C

Sample Paper Class 12 Biology Term 2 Set A

Sample Paper Class 12 Biology Term 2 Set A

SECTION – A

1. Differentiate between pro-insulin and mature insulin.
Answer : Pro- insulin contains an extra stretch called the C peptide which is not present in the mature insulin.

2. What are the two major causes of loss of biodiversity?
Answer : (i) Habitat destruction
(ii) Alien species invasion

3. Write the level of biodiversity represented by a mangrove. Give another example falling in the same level.
Answer : Ecological diversity is found in mangrove. 
Rainforests also show same level of biodiversity.

4. Identify ‘a’ and ‘b’ in the figure given below representing proportionate number of major vertebrate taxa.   

Answer : (a) Mammals (b) Amphibians

5. Assertion : Rennet and fruit extract of Withania somnifera have antagonistic functions.
Reason : Rennet is obtained from calf ’s stomach and is used for curdling of milk.
(a) Both assertion and reason are true, and reason is the correct explanation of assertion.
(b) Both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
Answer : (d)

6. Assertion : Dendritic cells originate in the bone marrow.
Reason : Dendritic cells are found in neuron.
(a) Both assertion and reason are true, and reason is the correct explanation of assertion.
(b) Both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
Answer : (c)

OR

Assertion : Brown sugar is morphine-derivative.
Reason : Morphine is the principal opium alkaloid.
(a) Both assertion and reason are true, and reason is the correct explanation of assertion.
(b) Both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
Answer : (b)

7. Read the following passage and answer the questions from 7(i) to 7(v) given below:
Some bird species follow army ants which walk on the forest floor. As the army ant colony travels on the forest floor, they stir up various flying insect species. As the insects flee, the birds following the ants catch the fleeing insects.

(i) Which population interaction is seen between the army ants and birds?
(a) Commensalism
(b) Amensalism
(c) Mutualism
(d) Predation
Answer : (a)

(ii) The type of interaction between birds and insects is
(a) commensalism
(b) amensalism
(c) mutualism
(d) predation.
Answer : (d)

(iii) Which of the following is predator in the given passage?
(a) Bird
(b) Insect
(c) Ant
(d) Both (a) and (b)
Answer : (a)

(iv) An advantage of interaction between birds and insects is
(a) it serves as conduit for energy transfer across trophic level
(b) it checks population of organisms of lower trophic level
(c) birds help in maintaining species diversity in a community, by reducing the intensity of competition  among competing prey species
(d) all of these.
Answer : (d)

(v) Read the given statements and select the correct option.
Statement A : Interaction between army ants and birds results in negative effect on the growth and survival of both the populations.
Statement B : Birds keep insects’ population under control.
(a) Statement A is correct but statement B is incorrect.
(b) Statement A is incorrect but statement B is correct.
(c) Both statements A and B are correct.
(d) Both statements A and B are incorrect.
Answer : (d)

SECTION – B

8. What are sticky ends? State their significance in recombination DNA technology.
Answer : Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands. This leaves
single stranded portions at the ends. These overhanging stretches on each strand are called sticky ends. They form hydrogen bonds with their complimentary counterparts and facilitate the action of DNA ligase enzyme.

OR

Explain the procedure by which PCR aids in early detection of cancer.
Answer : A single stranded DNA or RNA is tagged with a radioactive molecule(probe) that allowed to hybridise to its complementary DNA in a clone of cells which is followed by detection using autoradiography. The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complementarity with the mutated gene. Hence, cancer induced mutation can be detected.

9. Name a genus of baculovirus. Why are they considered good biocontrol agents?
Answer : Nucleopolyhedrovirus, a genus of baculoviruses, are useful in controlling many insects and other arthropods.
They are species specific narrow spectrum bioinsecticides with no side effects on plants, mammals, birds, fish and non-target insects. Therefore, they serve as an important component of integrated pest management programme in dealing with ecological sensitive areas.
These properties are useful in organic farming.

10. (a) Highlight the role of thymus as a lymphoid organ.
(b) Name the cells that mature in the above mentioned organ. Mention how they help in immunity.
Answer : (a) Thymus is a primary lymphoid organ where the maturation of T-lymphocytes takes place. Thymus is quite large in size at the time of birth but it atrophies with age.
(b) T-lymphocytes are produced in bone marrow, and they mature and are released from thymus. T cells provide cell-mediated immunity and defend against pathogens including protists and fungi that enter the cells.

11. Mention the term used to describe a population interaction between an orchid growing on a forest tree.
Answer : The population interaction is commensalism between an orchid growing on a forest tree in which orchid is benefitted and forest tree remains unaffected.

SECTION – C

12. (a) Mention important functions of activated sludge in a sewage treatment plant.
(b) What is the role of flocs in sewage treatment?
Answer : (a) A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the activated sludge is pumped
into large tanks called anaerobic sludge digesters.
The anaerobic bacteria present in this tank, digest the organic mass and aerobic bacteria and fungi in sludge and produce mixture of gases like methane, hydrogen sulphide and CO2 which constitute biogas.
(b) Flocs are masses of aerobic bacteria held together by slime and fungal filaments to form mesh like structures.
These microbes digest a lot of organic matter converting it into microbial biomass and releasing a lot of minerals to reduce the biochemical oxygen demand or BOD.

13. Explain the process of RNA interference.
Answer : Different steps involved in RNA interference are as follows:
(i) Double stranded RNAs are processed into approximately 21-23 nucleotide RNAs with two nucleotides. An RNase enzyme called dicer cuts the dsRNA molecules (from a virus, transposon, or through transformation) into small interfering RNAs (siRNAs).
(ii) Each siRNA complexes with ribonucleases (distinct from dicer) to form an RNA-induced silencing complex (RISC).
(iii) The siRNA unwinds and RISC is activated.
(iv) The activated RISC targets complementary mRNA molecules. The siRNA strands act as guides where the RISCs cut the transcripts in an area where the siRNA binds to the mRNA. This destroys the mRNA.
(v) When mRNA of the parasite is destroyed no protein is synthesised. It results in the death of the parasite in the transgenic host.

OR

Refer to the given figure and answer the following questions.
(i) Name the organism in which the vector is inserted to get the copies of the desired gene.
(ii) Mention the area labelled in the vector responsible for controlling the copy number of the inserted gene.
(iii) Name and explain the role of a selectable marker shown in the vector.   

Answer : (i) Escherichia coli
(ii) Origin of replication (ori) is a sequence from where replication starts and is also responsible for controlling the copy number of the inserted gene.
(iii) The given vector contains ampR as selectable marker.
It helps in selecting transformants (host cells containing vector) and eliminating non-transformants. Host cells containing ampR are resistant to antibiotic ampicillin.

SECTION – D

14. (a) Spleen acts as a lymphoid organ. Justify the statement.
(b) Differentiate between the following:
(i) Innate and acquired immunity
(ii) B – lymphocytes and T – lymphocytes
(c) What are antigen presenting cells? Mention its types.
Answer : (a) Spleen acts as a secondary lymphoid organ where mature B and T lymphocytes undergo proliferation and differentiation. In spleen, lymphocytes develop immune
response and become effector cells.
(b) (i) Differences between innate and acquired immunity are as follows:

(ii) Differences between the B-lymphocytes (B-cells) and T-lymphocytes (T-cells) are :

(c) The cells that engulf antigens and present their fragments to T-cells are called antigen presenting cells (APCs). There are three types of APCs found in the body :
(i) Macrophages, (ii) Dendritic cells, (iii) B-cells.

OR

How sewage water is treated before it could be discharged into natural water bodies?
Answer : Sewage water can be purified by passing it through sewage treatment plants with the action of microorganisms. A sewage treatment plant separates solids from liquids by physical processes and purifies the liquid by biological processes. There are three stages of this treatment; primary, secondary and tertiary. Primary treatment is physical, secondary is biological and tertiary is chemical. Primary treatment phase of sewage treatment removes floating and suspended solids from sewage through two processes of filtration and sedimentation. First floating matter is removed through sequential filtration. The filtrate is kept in large open settling tanks where grit settles down. Aluminium or iron sulphate is added in certain places to flocculation and settling down of solids. The sediment is called primary sludge while the supernatant is called effluent. The primary sludge traps a lot of microbes and debris. It is subjected to composting or land fill where anaerobic digestion removes the organic matter. During secondary treatment, the primary effluent is taken to aeration tanks. A large number of aerobic heterotrophic microbes grow in the aeration tank. They form flocs. Flocs are masses of bacteria held together by slime and fungal filaments to form mesh-like structures. The microbes digest a lot of organic matter, converting it into microbial biomass and releasing a lot of minerals. As a result the BOD of the waste matter is reduced to 10-15% of raw sewage, it is passed into settling tank. In settling tank, the bacterial flocs are allowed to undergo sedimentation. The effluent or supernatant is generally passed into natural water bodies and sediment of settling tank is called activated sludge.

15. Describe by diagrammatic representation of the process of recombinant DNA technology.
Answer : Diagram showing various steps of recombinant DNA technology is given below:

OR

(a) Describe the different steps in one complete cycle of PCR.
(b) State the purpose of such an amplified DNA sequence.
Answer : (a) Polymerase chain reaction (PCR) is a technique of synthesising multiple copies of the desired gene (DNA segment) in vitro. The basic requirements of PCR are DNA template, two oligonucleotide primers usually 20 nucleotides long, dNTPs and DNA polymerase which is stable at high temperature (usually Taq polymerase). Working mechanism of PCR is as follows : (i) Denaturation : The target DNA (DNA segment to be amplified) is heated to high temperature (94°C – 96°C). Heating results in the separation of two strands of DNA. Each of the two strands of the target DNA now act as template for synthesis of new DNA strand.
(ii) Annealing : During this step, two oligonucleotide primers hybridise to each of single stranded template DNA in presence of excess of synthetic oligonucleotides.
(iii) Extension : During this step, the enzyme DNA polymerase synthesises the DNA segment between the primers. Taq DNA polymerase, isolated from a thermophilic bacterium Thermus aquaticus, is used in most of the cases. This step requires presence of deoxynucleotide triphosphates (dNTPs) and Mg2+ and occurs at 72°C.
(b) Applications of PCR are :
(i) Diagnosis of pathogens
(ii) Diagnosis of specific mutations
(iii) DNA fingerprinting
(iv) In prenatal diagnosis
(v) In gene therapy.