Bihar Board Class 12 Biology Model Paper 2025–26 PDF With Answers – 100 Marks Complete Paper Pattern, Important Questions & Solutions”

“Bihar Board Class 12th Biology Model Paper 2025–26”
जो Board Exam Pattern (Objective + Subjective) के अनुसार तैयार किया गया है।
यह Paper 100 Marks के अनुसार बनाया गया है और इसमें MCQ + Short Answer + Long Answer Questions शामिल हैं — साथ ही उत्तर भी दिए गए हैं ताकि आप प्रैक्टिस कर सकें।

🧬 Bihar Board Class 12 Biology Model Paper 2025–26

Time: 3 Hours
Full Marks: 100
(Objective – 35 Marks, Subjective – 65 Marks)

🔹 A. Objective Type Questions (1 × 35 = 35 Marks)

प्रत्येक प्रश्न के सही उत्तर को चुनिए — एक ही विकल्प सही है।

1. Photosynthesis mainly occurs in which part of the plant?
   a) Root b) Stem ✅ c) Leaf d) Flower

2. In photosynthesis, the oxygen comes from:
   a) CO₂ ✅ b) H₂O c) Glucose d) Chlorophyll

3. Which hormone regulates the rate of transpiration?
   a) Auxin b) Cytokinin ✅ c) Abscisic acid d) Ethylene

4. Which part of nephron is responsible for filtration?
   ✅ a) Bowman’s Capsule b) Henle’s Loop c) Collecting Duct d) Tubule

5. Human RBCs do not have:
   a) Cytoplasm ✅ b) Nucleus c) Haemoglobin d) Cell membrane

6. The universal donor blood group is:
   ✅ a) O− b) AB+ c) B+ d) A+

7. Which law of Mendel is based on monohybrid cross?
   ✅ a) Law of Segregation b) Law of Dominance c) Law of Independent Assortment d) Law of Variation

8. DNA replication occurs during which phase?
   a) G₁ ✅ b) S-phase c) G₂ d) M-phase

9. Which of the following is a vector for malaria?
   ✅ a) Female Anopheles mosquito b) Male Anopheles c) Housefly d) Sand fly

10. Insulin is secreted by:
    ✅ a) Pancreas b) Liver c) Adrenal gland d) Pituitary

11. Human genome contains approximately how many genes?
    a) 20,000–25,000 ✅ b) 30,000 c) 50,000 d) 10,000

12. Which gas damages ozone layer?
    ✅ a) CFC b) CO₂ c) O₃ d) N₂

13. Which part of the brain controls heartbeat?
    ✅ a) Medulla oblongata b) Cerebrum c) Cerebellum d) Pons

14. Nitrogen fixation is done by:
    ✅ a) Rhizobium b) E. coli c) Fungi d) Yeast

15. DNA fingerprinting was developed by:
    ✅ a) Alec Jeffreys b) Watson c) Crick d) Mendel

🔹 B. Short Answer Type Questions (3 × 10 = 30 Marks)

प्रत्येक प्रश्न का उत्तर लगभग 60 शब्दों में दीजिए।

1. Define transpiration and list its types.
   Answer:
   Transpiration is the loss of water in the form of vapor from aerial parts of the plant.
   Types: Stomatal, Cuticular, Lenticular.

2. What is double fertilization in plants?
   Answer:
   In angiosperms, one male gamete fuses with egg (syngamy) forming zygote, and the other fuses with two polar nuclei (triple fusion) to form endosperm. Hence, it’s called double fertilization.

3. Write two differences between DNA and RNA.
   Answer:

   DNA	RNA
   Double stranded	Single stranded
   Deoxyribose sugar	Ribose sugar

4. What is vaccination? How does it help in immunity?
   Answer:
   Vaccination is administration of antigenic material to stimulate immune response and create memory cells. It provides active immunity against diseases.

5. Write a note on ecosystem.
   Answer:
   An ecosystem is a self-sustaining unit consisting of biotic and abiotic components interacting with each other, like a pond or forest.

6. Explain the role of placenta in humans.
   Answer:
   Placenta acts as an interface between mother and fetus, providing nutrients, oxygen, and removing wastes.

7. What is amniocentesis? Why is it banned?
   Answer:
   It’s a prenatal diagnostic test to detect chromosomal disorders. Banned due to misuse for female foeticide.

8. Define ex-situ conservation with examples.
   Answer:
   Conservation of species outside their natural habitat, e.g., zoo, botanical garden, seed bank.

9. Write the full form of PCR. What is its use?
   Answer:
   PCR – Polymerase Chain Reaction; used to amplify DNA sequences in biotechnology.

10. Explain artificial selection with one example.
    Answer:
    Artificial selection is human-controlled breeding for desirable traits, e.g., improved crop varieties or dog breeds.

🔹 C. Long Answer Type Questions (5 × 7 = 35 Marks)

प्रत्येक प्रश्न का उत्तर लगभग 150 शब्दों में दीजिए।

1. Explain the structure and function of the human heart with labeled diagram.
   Answer (summary):
   The human heart is a four-chambered organ — right atrium, right ventricle, left atrium, left ventricle. It pumps deoxygenated blood to lungs and oxygenated blood to body. (Diagram should show valves and major vessels.)

2. Describe the process of photosynthesis and the role of light and dark reactions.
   Answer:
   Photosynthesis has two phases — Light reaction (ATP, NADPH formation in thylakoid) and Dark reaction (Calvin cycle in stroma forming glucose from CO₂ using ATP and NADPH).

3. What are Mendel’s three laws of inheritance? Explain with example.
   Answer:

   1. Law of Dominance

   2. Law of Segregation

   3. Law of Independent Assortment
      Example: Pea plant experiments — round/wrinkled, tall/dwarf traits.

4. Explain human reproductive system (male & female) with diagram and functions.
   Answer:
   Describe organs: Testes, Vas deferens, Ovary, Fallopian tube, Uterus, etc. Functions — gamete production, fertilization, hormone secretion.

5. What is ecosystem productivity? Explain types of productivity.
   Answer:
   Productivity is the rate of biomass production.

   • Gross Primary Productivity (GPP)

   • Net Primary Productivity (NPP)

   • Secondary Productivity (consumers)

📘 Section D – Value Based / Application Question (5 Marks)

Q: Deforestation has increased carbon dioxide in the atmosphere. Explain its effect on environment and how can we control it?
Answer:

• Increased CO₂ causes global warming, melting of glaciers, and climate change.

• Controlled by: Afforestation, renewable energy use, reducing fossil fuel consumption.

✅ Answer Key Summary

Download the latest Bihar Board 12th Biology Model Paper 2025–26 (With Answers). Get full 100 marks paper pattern, MCQs, Short & Long Questions with solutions — prepared as per the new BSEB syllabus for Board Exam 2026.