PSEB CLASS 12 BIOLOGY GUESS PAPER MARCH 2026 SET 2

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PUNJAB SCHOOL EDUCATION BOARD

GUESS PAPER (SET-2)

CLASS: 12th (BIOLOGY)

SESSION: 2025-26

Time: 3 Hours Maximum Marks: 70

Note:

1. Question paper consists of four sections A, B, C and D with a total of 19 questions.
2. Section-A contains question number 1 having 20 parts of 1 mark each (12 MCQs, 4 Fill in the blanks, 4 True/False).
3. Section-B contains questions number 2 to 11 (10 short answer type questions of 2 marks each). Questions 4, 5, 9, 11 have internal choice.
4. Section-C contains questions number 12 to 16 (5 questions of 3 marks each). Questions 12 and 15 have internal choice.
5. Section-D consists of questions 17 to 19 (3 questions of 5 marks each). All questions have 100% internal choice.

SECTION A

(Each question carries 1 mark)

Q1. Multiple Choice Questions (I-XII):

I. The exine of pollen grain is made up of:
a. Cellulose
b. Lignin
c. Sporopollenin
d. Pectin

II. The hormone responsible for initiation of spermatogenesis is:
a. Testosterone
b. FSH
c. LH
d. GnRH

III. The method that prevents ovulation by inhibiting LH surge is:
a. Copper-T
b. Barrier method
c. Oral pills
d. Vasectomy

IV. ABO blood group inheritance is an example of:
a. Polygenic inheritance
b. Complete dominance
c. Codominance
d. Incomplete dominance

V. The start codon for translation is:
a. UAA
b. UAG
c. AUG
d. UGA

VI. The wings of birds and bats are an example of:
a. Homologous organs
b. Analogous organs
c. Vestigial organs
d. Atavistic organs

VII. The BCG vaccine protects against:
a. Smallpox
b. Polio
c. Tuberculosis
d. Hepatitis B

VIII. The first antibiotic discovered was:
a. Streptomycin
b. Penicillin
c. Tetracycline
d. Erythromycin

IX. Restriction enzymes belong to the class of:
a. Ligases
b. Endonucleases
c. Exonucleases
d. Polymerases

X. Bt cotton is resistant to:
a. Aphids
b. Bollworm
c. Whitefly
d. Thrips

XI. Lichens represent an example of:
a. Parasitism
b. Mutualism
c. Competition
d. Amensalism

XII. Which category of IUCN indicates highest risk of extinction?
a. Vulnerable
b. Endangered
c. Critically endangered
d. Rare

State True or False (XIII-XVI):

XIII. Menstrual cycle stops during pregnancy.

XIV. The genetic code is overlapping in nature.

XV. Antibiotics are effective against viral infections.

XVI. Mutualism is essential for survival of both interacting species.

Fill in the Blanks (XVII-XX):

XVII. __________ is the surgical method of contraception in females.

XVIII. DNA is a polymer of __________.

XIX. Golden rice was developed to combat __________ deficiency.

XX. The main source of energy for all ecosystems is __________.

SECTION B

(Each question carries 2 marks)

Q2. Why is an apple considered a false fruit?

Q3. State two roles of Sertoli cells in spermatogenesis.

Q4. Why is sex education necessary in schools?

OR

Write the full form of:
a) ICSI
b) ZIFT

Q5. State any two differences between genotype and phenotype.

OR

Write two differences between linkage and crossing over.

Q6. State two differences between homologous and analogous organs.

Q7. Write difference between B-cells and T-cells.

Q8. Mention two roles of microbes in sewage treatment.

Q9. State two properties of an ideal cloning vector.

OR

Write two differences between sticky and blunt ends.

Q10. Give two reasons why Bt crops are environment-friendly.

Q11. State two reasons for higher biodiversity in tropics.

OR

Differentiate between commensalism and amensalism.

SECTION C

(Each question carries 3 marks)

Q12. Explain why DNA is considered a better genetic material than RNA.

OR

Describe transcription in eukaryotes including post-transcriptional modifications.

Q13. Describe adaptive radiation with reference to Darwin’s finches.

Q14. Describe the life cycle of Plasmodium in humans and mosquitoes.

Q15. Explain the steps involved in polymerase chain reaction (PCR).

OR

Describe RNA interference mechanism in eukaryotes.

Q16. Explain predator–prey interaction with ecological significance.

SECTION D

(Each question carries 5 marks)

Q17. Describe the process of spermatogenesis with hormonal regulation.

OR

With a neat labeled diagram, describe the parts of a typical angiospermic ovule.

Q18. Explain inheritance of ABO blood groups in humans with a chart.

OR

Explain translation in detail with initiation, elongation and termination.

Q19. Explain the major causes of biodiversity loss (The Evil Quartet).

OR

Read the passage carefully and answer the following questions:

Primary productivity refers to the rate at which producers synthesise organic matter. Gross primary productivity (GPP) is the total organic matter produced, while net primary productivity (NPP) is the portion available to consumers after respiratory losses. Different ecosystems show variations in productivity depending on climatic conditions and availability of nutrients.

1. Differentiate between GPP and NPP. (2)
2. Why is NPP important for heterotrophs? (1)
3. Name one ecosystem with high primary productivity. (1)
4. Mention one factor affecting primary productivity. (1)

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