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| CBSE Class 12 Biology PreBoard Paper |
| Sample Paper |
| CLASS – XII Year: 2025-2026 |
| SUBJECT – Biology (044) |
General Instructions: CBSE Class 12 Biology PreBoard Paper
Please read the following instructions very carefully and strictly follow them: CBSE Class 12 Biology PreBoard Paper
(i) This question paper contains 33 questions. All questions are compulsory. CBSE Class 12 Biology PreBoard Paper
(ii) The question paper is divided into five sections – Sections A, B, C, D, and E. CBSE Class 12 Biology PreBoard Paper
(iii) Section A – questions number 1 to 12 are multiple-choice type questions. Each question carries 1 mark. For Questions number 13 to 16, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer from the codes (A), (B), (C), and (D) as given below.
(iv) Section B – questions number 17 to 21 are very short answer-type questions. Each question carries 2 marks. CBSE Class 12 Biology PreBoard Paper
(v) Section C – questions number 22 to 28 are short-answer type questions. Each question carries 3 marks. CBSE Class 12 Biology PreBoard Paper
(vi) Section D – questions number 29 and 30 are case-based questions. Each question carries 4 marks. CBSE Class 12 Biology PreBoard Paper
(vii) Section E – questions number 31 to 33 are long-answer type questions. Each question carries 5 marks. CBSE Class 12 Biology PreBoard Paper
Section A
This section comprises 12 Multiple Choice Questions (MCQs) of 1 mark each. 12x 1=12
1. Pyramid of energy is :
| A. Always upright | B. Both Always inverted and Always upright | C. Sometimes inverted sometimes upright | C. Sometimes inverted, sometimes upright |
2. Which of the following birth control measures can be considered the safest?
| A. Termination of unwanted pregnancy | B. The rhythm method | C. The use of physical barriers | D. Sterilisation techniques |
3. The multipurpose protected area, which is meant for preserving Genetic diversity in the representative ecosystem, is called __.
| A. National parks | B. Protected areas | C. Biosphere reserves | D. Sanctuaries |
4. In a population, the condition at which the rate of addition of new members is more than the rate of individuals lost indicates :
| A. Zero population growth | B. Fluctuating growth | C. Exponential growth | D. Declining growth |
5. The bp of the DNA double helix is given. Suitable mRNA strand that is derived from transcription of 3’ ATTTCC 5’ is 5’ TAAAGG3’:1
| A. UAAAGG | B. CUUUCC | C. GAAAGG | D. CCUUUC |
6. Which of the following is now being commercially produced by biotechnological procedures?
| A. Nicotine | B. Insulin | C. Morphine | D. Quinine |
7. A woman with normal vision, but whose father was colour-blind, marries a colour-blind man. Suppose that the fourth child of this couple was a boy. This boy:
| A. May be colour-blind or may be of normal vision | B. Must be colour-blind | C. Will be partially colour-blind since he is heterozygous for the colour blind mutant allele | D. Must have normal colour vision |
8. The picture shown below is an example of :
| A. Convergent evolution of Australian marsupials and placental mammals | B. Divergent evolution of Australian marsupials and placental mammals | C. Homologous organs of both animals | D. Analogous organs of both animals |
9. During the food chain, the maximum energy is stored in:
| A. Carnivores | B. Producers | C. Decomposers | D. Herbivores |
10. Study the pedigree chart of a certain family given below and select the correct conclusion which can be drawn for the character:
| A. The trait under study could not be colour blindness | B. The female parent is heterozygous | C. The male parent is homozygous dominant | D. The parent could not have had a normal daughter for this character |
11. Monascus purpureus is a yeast commercially used in the production of :
| A. Citric acid | B. Ethanol | C. Statins | D. Streptokinase |
12. Arrange the following steps that are shown in the figure :
| A. The plasmid is taken up into a bacterial cell which makes protein directed by human DNA | A. The plasmid is taken up into a bacterial cell, which makes protein directed by human DNA | C. The segment of DNA removed from human cell | C. The segment of DNA removed from a human cell a) 1→4→3→2 b) 4→3→2→1 c) 1→2→3→4 d) 2→3→4→1 |
Assertion-Reason based
For Questions 13 to 16, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer from the codes (A), (B), (C) and (D) as given below. CBSE Class 12 Biology PreBoard Paper
(A) Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of the Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.
13. Assertion (A): Condoms are barriers made of a thin rubber/latex sheath, and their use has increased in recent years.
Reason (R): It prevents conception, and its additional benefit is protecting the user from contracting STDs and AIDS.
14. Assertion (A): Different types of alcoholic drinks depend on the type of raw material used for fermentation.
Reason (R): With or without distillation, different types of alcoholic drinks are obtained.
15. Assertion (A): Net primary productivity is always less than Gross primary productivity in an ecosystem.
Reason (R): A considerable amount of Gross primary productivity is utilised by plants in respiration.
16. Assertion (A): Ramapithecus was more man, while Dryopithecus was more ape-like.
Reason (R): These primates were hairy and walked like gorillas and chimpanzees.
Section B
17. What was the speciality of the milk produced by the transgenic cow Rosie?
OR
How are GM plants better than normally grown plants? (any 4 points)
18. The flow of genetic information is shown below. Name the process of (a) and (b).
19. In the diagram given below, show the path of a pollen tube from the pollen on the stigma into the embryo sac. Name the components of the egg apparatus.
OR
Write four characteristics of an insect-pollinated flower.
20. Given below is an incomplete chart showing the influence of hormones on gametogenesis in males. Observe the chart and fill in the blanks A, B, C and D.
21. Give two examples of natural predators of insect pests.
OR
Bottled fruit juices are clearer than those made at home. Explain.
SECTION C
22. Study the given portion of the double-stranded polynucleotide chain carefully. Identify a, b, c and d.
23. How do the alleles of particular genes differ from each other? Explain its significance.
24. Define the following terms and give one example for each:
a. Commensalism b. Parasitism c. Camouflage d. Mutualism e. Interspecific competition
25. (a) Given below is the stepwise schematic representation of the process of electrophoresis. Identify the alphabet representing (i) the Anode end, (ii) the smallest/lightest DNA strand in the matrix, (iii)the Agarose gel
b. What is elution? State the importance of elution in this process.
26. Write short notes on the following:
I. Wildlife sanctuary II. Biosphere reserves
27. Define the terms:
I. Palaeontology II. Phylogeny III. Fossils
28. Prevention is better than cure is an apt slogan to safeguard adolescents from drug abuse. List any 6 steps that could be taken in this regard.
SECTION D
29. Read the following text carefully and answer the questions that follow :
The following is the illustration of the sequence of ovarian events (A-I) in a human female.SE Class 11 Biology Half Yearly Paper
I. Identify the figure that illustrates ovulation and mention the stage of the menstrual cycle it represents.
II. Name the ovarian hormone and the pituitary hormone that have caused the above-mentioned event.
III. Explain the changes that occur in the uterus simultaneously in anticipation.
OR
Write the differences between C and H.
30. Read the following text carefully and answer the questions that follow :
The diagram shows the replication of the retrovirus in the host.
I. Fill in the missing data in boxes labelled 1 & 2.
II. Why is it named a retrovirus?
III. While the virus is being replicated and released, does the infected cell survive and why do the virus-infected cells prevent the spreading of the virus to healthy cells?
OR
What is the effect of HIV infection on the immune system?BSE Class 11 Biology Half Yearly Paper
SECTION E
31. Draw a labelled sketch of L.S. of the pistil showing the process of double fertilisation.
Or
Draw a diagram of the male gametophyte of an angiosperm. Label any four parts. Why is sporopollenin considered the most resistant organic material?
32. Define an operon. Giving an example, explain an Inducible operon.
OR
Name and describe the steps involved in the technique widely used in forensics that serves as the basis of paternity testing in case of disputes.
33. Bioreactors are vessels that have been designed and produced to provide an effective environment for enzymes or whole cells to transform biochemicals into products. In some cases, inactivation of cells or sterilisation is carried out in a bioreactor, such as in water treatment. The development of bioreactors is required to produce large quantities of products.
I. Give optimum growth conditions used in bioreactors.
II. Draw a well-labelled diagram of a simple stirred-tank bioreactor.
III. How does a simple stirred tank bioreactor differ from a sparged stirred tank bioreactor?
OR
Recombinant DNA (rDNA) is a technology that uses enzymes to cut and paste together DNA sequences of interest. The recombined DNA sequences can be placed into vehicles called vectors that ferry the DNA into a suitable host cell, where it can be copied or expressed.
I. A bacterial cell is shown in the figure given below. Label the parts ‘A’ and ‘B’. Also, mention the use of part A in rDNA technology.
II. Suppose a linear DNA fragment and a plasmid have three restriction sites for EcoRl. How many fragments will be produced from linear DNA and plasmid, respectively?
(ii) Photolysis of water
(iii) End products (b) The final stage of aerobic respiration involves the synthesis of the maximum ATP. Name the metabolic pathway and its location in the cell.