PSEB CLASS 12 BIOLOGY GUESS QUESTION PAPER 2026

 PUNJAB SCHOOL EDUCATION BOARD (PSEB)

CLASS 12 – BIOLOGY
GUESS QUESTION PAPER
SESSION: 2025–26

Time: 3 Hours
Maximum Marks: 70

Important Instructions:

1. All questions are compulsory.

2. The question paper consists of four sections A, B, C and D.

3. Use neat and clean diagrams wherever required.

4. Internal choices are provided as per question paper pattern.

🔹 SECTION – A

(1 × 20 = 20 Marks)

Multiple Choice Questions (12)

1. The phenomenon where the ovary develops into a fruit without fertilization is called.
   a) Parthenocarpy
   b) Apomixis
   c) Asexual reproduction
   d) Sexual reproduction

2. The nuclei present in central cell of embryo sac is called
   a) Egg nuclei
   b) Antipodal nuclei
   c) Polar nuclei
   d) Synergid nuclei

3. Which Artificial Reproductive Technique can help a lady conceive a child if both her fallopian tubes are blocked?
   a) IUD
   b) IVF
   c) ZIFT
   d) GIFT

4. Vertebrate forelimbs are example of
   a) Homologous organs
   b) Analogous organs
   c) Vestigial Organ
   d) Nonfunctional organ

5. If BOD of water sample is very high, the sample is
   a) Highly polluted
   b) Less polluted
   c) Not polluted
   d) Potable

6. The term molecular scissors generally refers to
   a) DNA polymerase
   b) RNA polymerase
   c) Restriction endonuclease
   d) DNA ligase

7. Which of the following is the start codon
   a) GGA
   b) UCA
   c) AUG
   d) CCU

8. Golden rice is enriched with
   a) Vitamin A
   b) Vitamin K
   c) Vitamin C
   d) Vitamin D

9. The concept of natural selection was proposed by
   a) Darwin
   b) Lamarck
   c) De Vries
   d) Cuvier

10. Tubectomy a method of population control is performed on
    a) Both male and female
    b) Male only
    c) Female only
    d) Only pregnant women

11. The genes causing cancer are
    a) Structural genes
    b) Promotor genes
    c) Oncogenes
    d) Regulatory genes

12. Mycorrhiza is example of
    a) Antibiosis
    b) Mutualism
    c) Commensalism
    d) Parasitism

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Fill in the Blanks (4)

13. Zygote divides to form __________ which is implanted in uterine wall.

14. PCR stands for ____________.

15. The Bt gene is isolated from the organism called ____________.

16. First biosphere reserve in India was ____________.

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True / False (4)

17. Vaccination is a type of innate immunity.

18. Biopiracy is the illegal use of bioresources.

19. Malaria is caused by bacteria transmitted by mosquito bites.

20. Largest population in a food chain are producers.

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🔹 SECTION – B

(Short Answer Type Questions)
(2 × 10 = 20 Marks)

Q2. Why is Apple called a false fruit? Which part of the flower forms a fruit?

Q3. Write two functions of tapetum.

Q4. What is amniocentesis? Why is it banned in India?
OR
What are the measures that should be taken to prevent STDs?

Q5. What do you mean by law of segregation?
OR
What will the progeny be if a woman carrier for haemophilia marries a normal man?

Q6. What are analogous organs? Give an example.

Q7. Differentiate between innate and acquired immunity.

Q8. Define sewage. Why is it harmful to us?

Q9. What are bioreactors? Name its two types.
OR
Expand PCR. Mention its any one importance in biotechnology.

Q10. Write two advantages of GM crops.

Q11. Write any two points of differences between grazing and detritus food chain.
OR
What do you mean by hotspots of biodiversity?

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🔹 SECTION – C

(Short Answer Type Questions)
(3 × 5 = 15 Marks)

Q12. What is DNA fingerprinting? Mention its two applications.
OR
Explain the structure of transcription unit with diagram.

Q13. What is adaptive radiation? Give an example.

Q14. Name the causing agent of Typhoid. Also write down its symptoms and modes of transmission.

Q15. With help of diagram, show the steps of recombinant DNA technology.
OR
What is gene therapy? Illustrate using the example of adenosine deaminase deficiency.

Q16. Name and explain the type of interaction between clown fish and sea anemone.

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🔹 SECTION – D

(Long Answer Type Questions)
(5 × 3 = 15 Marks)

Q17. Draw a labelled diagram of an anatropous ovule and explain its parts.
OR
Define Oogenesis. Briefly describe the process of Oogenesis with the help of labelled diagram.

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Q18. Explain replication of DNA with a diagram.
OR
Describe characteristics of chromosomal abnormalities:

1. Trisomy of 21st chromosome

2. XXY

3. XO

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Q19. Describe various causes of loss of biodiversity.
OR
Read the passage carefully and answer the following questions:

A stable self supporting ecological unit, resulting from an interaction between biotic community, living organisms and its biotic environment is called ecosystem. An ecosystem comprises two main components, biotic including plants, animals, microorganisms and abiotic including substratum, water, minerals, pH, carbon dioxide, oxygen, and temperature. It must also receive a constant supply of light energy.

1. What is an ecosystem?

2. Name two major kinds of ecosystems.

3. Name three abiotic components of ecosystem.

4. Give one example of man made ecosystem.

5. Give one example of terrestrial ecosystem.

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