Class 12 Biology Guess Paper 2025 – BSEB | Download PDF, Questions, Answers & More!

Are you a student of the Bihar Board Class 12 preparing for your Biology exam in 2025? Looking for a smart and focused way to revise important topics?

This Class 12 Biology Guess Paper 2025 is designed exactly for you!

It includes a mix of objective, short-answer, and long-answer questions, strictly based on the BSEB (Bihar School Examination Board) pattern. Practicing this will not only boost your confidence but also increase your chances of scoring high.

Overview – BSEB Class 12 Biology Guess Paper 2025

• Board: Bihar School Examination Board (BSEB)

• Subject: Biology

• Class: 12th

• Total Marks: 70

• Time Duration: 3 Hours

• Paper Type: Objective + Subjective

• Focus Keyword: Class 12 Biology Guess Paper 2025

 General Instructions

• All questions are compulsory.

• Marks are mentioned next to each question.

• Draw neat, labeled diagrams where necessary.

• The use of calculators is strictly prohibited.

Section A – Objective Type Questions (35 × 1 = 35 Marks)

(Each question carries 1 mark. Choose the correct option.)

Q1. The functional unit of the kidney is:
(a) Nephron
(b) Neuron
(c) Glomerulus
(d) Ureter

Answer: (a) Nephron

Q2. Which gas is released during photosynthesis?
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Hydrogen

Answer: Oxygen

Q3. The universal donor blood group is:
(a) A
(b) AB
(c) O
(d) B

Answer: O

Q4. Which of the following is a prokaryote?
(a) Amoeba
(b) Yeast
(c) Bacteria
(d) Hydra

Answer:Bacteria

Q5. Mendel is known as the Father of:
(a) Botany
(b) Genetics
(c) Evolution
(d) Cytology

Answer: genetics

Q6. Which organelle is known as “Powerhouse of the cell”?
(a) Ribosome
(b) Nucleus
(c) Mitochondria
(d) Golgi body

Answer : mitochondria

Q7. DNA Fingerprinting is mainly used in:
(a) Food production
(b) Forensics
(c) Agriculture
(d) Weather forecast

Answer: Forensics

Q8. The causative organism of Malaria is:
(a) Trypanosoma
(b) Plasmodium
(c) Entamoeba
(d) Giardia

Answer: Plasmodium

Q9. Which of the following is a plant hormone?
(a) Insulin
(b) Auxi
(c) Thyroxine
(d) Adrenaline

Answer: Auxin

Q10. Fertilization in the human female normally occurs in:
(a) Ovary
(b) Uterus
(c) Fallopian tube
(d) Cervix

Answer: Fallopian tube

Q11. Which vitamin is synthesized in the skin by sunlight?
(a) Vitamin C
(b) Vitamin D
(c) Vitamin B12
(d) Vitamin A

Answer: Vitamin D

Q12. In meiosis, the number of chromosomes is:
(a) Doubled
(b) Reduced to half
(c) Remains the same
(d) Becomes four times

Answer: Reduced to half

Q13. The study of fossils is called:
(a) Morphology
(b) Palaeontology
(c) Ecology
(d) Taxonomy

Answer: Palaeontology

Q14. The site of protein synthesis in a cell is:
(a) Ribosome
(b) Mitochondria
(c) Golgi body
(d) Lysosome

Answer: Ribosome

Q15. Which one of the following is an STD?
(a) Syphilis
(b) Polio
(c) Asthma
(d) Diabetes

Answer: Syphilis

Q16. Which blood group is a universal recipient?
(a) O
(b) AB
(c) A
(d) B

Answer: AB

Q17. The largest gland in the human body is:
(a) Pancreas
(b) Kidney
(c) Liver
(d) Thyroid

Answer: liver

Q18. Which of the following is caused by a virus?
(a) Cholera
(b) Tuberculosis
(c) AIDS
(d) Malaria

Answer: AIDS

Q19. The smallest unit of the nervous system is:
(a) Brain
(b) Nephron
(c) Neuron
(d) Axon

Answer: Neuron

Q20. The process of conversion of milk into curd is due to:
(a) Yeast
(b) Lactobacillus
(c) Virus
(d) Algae

Answer: Lactobacillus

Q21. The first step of respiration is:
(a) Glycolysis
(b) Krebs cycle
(c) Electron transport system
(d) Fermentation

Answer: Glycolysis

Q22. Which of the following is a fossil fuel?
(a) Water
(b) Petroleum
(c) Sunlight
(d) Wind

Answer: Petroleum

Q23. Which structure controls all activities of the cell?
(a) Ribosome
(b) Nucleus
(c) Mitochondria
(d) Vacuole

Answer: Nucleus

Q24. The exchange of gases in plants takes place through:
(a) Xylem
(b) Phloem
(c) Stomata
(d) Root hairs

Answer: Stomata

Q25. The causative organism of Tuberculosis is:
(a) Mycobacterium
(b) Plasmodium
(c) Virus
(d) Fungi

Answer: Mycobacterium

Q26. Which of the following is a sex-linked disease?
(a) Colour blindness 
(b) Typhoid
(c) Malaria
(d) Cholera

Answer: Colour blindness

Q27. The monomers of proteins are:
(a) Glucose
(b) Amino acids
(c) Fatty acids
(d) Nucleotides

Answer: Amino acids

Q28. Which one of the following helps in the clotting of blood?
(a) RBC
(b) WBC
(c) Platelets
(d) Plasma

Answer: Platelets

Q29. Which organ secretes bile juice?
(a) Pancreas
(b) Stomach
(c) Liver
(d) Kidney

Answer: Liver

Q30. The study of heredity and variation is called:
(a) Genetics
(b) Cytology
(c) Physiology
(d) Embryology

Answer: Genetics

Q31. The green pigment in plants is:
(a) Carotene
(b) Chlorophyll
(c) Xanthophyll
(d) Anthocyanin

Answer: Chlorophyll

Q32. Which is known as the “Brain of the computer”?
(a) CPU
(b) DNA
(c) RNA
(d) Neuron

Answer: CPU

Q33. Darwin proposed the theory of:
(a) Natural Selection
(b) Inheritance
(c) Cell theory
(d) Germ theory

Answer: Natural Selection

Q34. Which disease is caused by a deficiency of insulin?
(a) Cancer
(b) Diabetes
(c) Goitre
(d) Rickets

Answer: Diabetes

Q35. The process of self-pollination occurs in:
(a) Cross flowers
(b) Bisexual flowers
(c) Unisexual flowers
(d) Artificial flowers

Answer: Bisexual flowers

Section B – Short Answer Questions (7 × 3 = 21 Marks)

Q36. Differentiate between Mitosis and Meiosis. (3 Marks)

Answer:

• Mitosis produces 2 diploid cells, Meiosis produces 4 haploid cells.

• Mitosis occurs in somatic cells, Meiosis in reproductive cells.

• Mitosis maintains chromosome number, Meiosis reduces it by half.

Q37. Write three differences between DNA and RNA. (3 Marks)

Answer:

• DNA has deoxyribose sugar, RNA has ribose sugar.

• DNA bases: A, T, G, C; RNA bases: A, U, G, C (U replaces T).

• DNA is double-stranded, RNA is single-stranded.

Q38. What is Genetic Drift? Give an example. (3 Marks)

Answer:

• Genetic drift is a random change in allele frequency in small populations.

• Example: Founder effect in isolated island populations.

Q39. Write the role of enzymes in digestion. (3 Marks)

Answer:

• Enzymes break down complex food into simple, absorbable molecules.

• Example: Amylase (starch → sugar), Pepsin (protein → peptides), Lipase (fats → fatty acids).

Q40. Mention three functions of the Human Skeleton. (3 Marks)

Answer:

• Provides shape and support to the body.

• Protects vital organs (e.g., skull protects brain).

• Helps in movement with muscles.

Q41. Write three harmful effects of drug addiction. (3 Marks)

Answer

• Causes damage to liver, brain, and lungs.

• Leads to mental disorders and poor memory.

• Results in social and financial problems.

Q42. Differentiate between Arteries and Veins. (3 Marks)

Answer

• Arteries carry oxygenated blood (except pulmonary artery), veins carry deoxygenated blood (except pulmonary vein).

• Arteries have thick, elastic walls, veins have thin walls with valves.

• Blood flow in arteries is away from heart, in veins towards heart.

Section C – Long Answer Questions (2 × 7 = 14 Marks)

Q43. Describe the structure and working of the Human Heart with a neat diagram. (7 Marks)

Answer

Answer:
The human heart is a muscular organ, roughly the size of a fist, located slightly left to the center of the chest. It acts as a pump that circulates blood throughout the body.

Structure of the Human Heart:

1. The heart is enclosed by a protective sac called the pericardium.

2. It has four chambers:

   • Right Atrium (RA): Receives deoxygenated blood from the body through the superior and inferior vena cava.

   • Right Ventricle (RV): Pumps deoxygenated blood to the lungs via the pulmonary artery.

   • Left Atrium (LA): Receives oxygenated blood from the lungs through the pulmonary veins.

   • Left Ventricle (LV): Pumps oxygenated blood to the entire body through the aorta.

3. The valves (tricuspid, bicuspid/mitral, pulmonary, and aortic valves) ensure unidirectional flow of blood.

4. The walls of the ventricles, especially the left ventricle, are thicker as they pump blood with greater force.

Working of the Human Heart (Double Circulation):

1. Deoxygenated blood from the body → Right Atrium → Right Ventricle → Lungs (via pulmonary artery) → Oxygenation occurs in lungs.

2. Oxygenated blood from lungs → Left Atrium → Left Ventricle → Aorta → Entire body.

This process ensures continuous circulation of oxygenated blood to tissues and removal of carbon dioxide.

Diagram Description:

• Draw a simple heart showing 4 chambers, vena cava, pulmonary artery, pulmonary vein, and aorta.

• Show arrows for blood flow (blue for deoxygenated, red for oxygenated).

Q44. Explain the process of Photosynthesis in detail with suitable diagrams. (7 Marks)

Answer:
Photosynthesis is the process by which green plants, algae, and some bacteria use sunlight to prepare food (glucose) from carbon dioxide and water, releasing oxygen as a by-product.

Equation of Photosynthesis:

6CO2+6H2O→Light, ChlorophyllC6H12O6+6O26CO₂ + 6H₂O \xrightarrow{\text{Light, Chlorophyll}} C₆H₁₂O₆ + 6O₂6CO2​+6H2​OLight, Chlorophyll​C6​H12​O6​+6O2​

Process of Photosynthesis:

1. Light Absorption:

   • Chlorophyll pigments present in the chloroplasts absorb sunlight, mainly red and blue wavelengths.

2. Photolysis of Water (Light Reaction):

   • Sunlight splits water molecules into oxygen, protons, and electrons.

   • 2H2O→4H++4e−+O2↑2H₂O → 4H⁺ + 4e⁻ + O₂ ↑2H2​O→4H++4e−+O2​↑

3. Formation of ATP and NADPH (Light Reaction):

   • Electrons move through electron transport chain (ETC) producing ATP and NADPH, which are energy carriers.

4. Carbon Fixation (Dark Reaction/Calvin Cycle):

   • Takes place in the stroma of chloroplasts.

   • CO₂ is fixed with the help of ATP and NADPH to form glucose (C₆H₁₂O₆).

5. End Products:

   • Glucose (used as food/energy storage).

   • Oxygen (released into the atmosphere).

Diagram Description:

• Draw a leaf structure showing sunlight, CO₂ entering stomata, water from roots, and O₂ released.

• Inside leaf → Chloroplast with light reaction (thylakoid) and dark reaction (stroma).

FAQs – Class 12 Biology Guess Paper 2025

Q1. Is this guess paper based on the latest BSEB syllabus?

Yes, this paper follows the latest Class 12 Biology syllabus prescribed by the Bihar Board for 2025.

Q2. Will questions from this guess paper come in the final exam?

While it’s not guaranteed, many questions are based on past year trends and frequently asked topics—making it highly useful for practice.

Q3. Can I download this Class 12 Biology Guess Paper 2025 as a PDF?

Yes! While this page provides the full content of the guess paper, you can save or print it directly from your browser for offline study. This way, you can revise anytime without needing internet access.

Q4. Are diagrams necessary in Biology long answers?

Absolutely! Diagrams help you score better and are essential in answers related to the heart, photosynthesis, etc.

 Conclusion: Class 12 Biology Guess Paper 2025

If you’re aiming to score well in the Class 12 Biology exam 2025, this Class 12 Biology Guess Paper 2025 will act as your last-minute revision guide. Covering the most important MCQs, short questions, and long-form answers, it gives you a clear idea of what to expect in the exam.

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