MP Board Class 12 Biology Previous Year Paper 2023 — Solved Questions with Answers

Are you preparing for the MP Board Class 12 Biology exam? This solved question paper of 2023 will help you understand the exam pattern, marking scheme, and important topics. We have provided detailed answers to all questions as per the official MP Board answer key.

📋 Paper Overview & Marking Scheme

🧬 Section A: Multiple Choice Questions (1 × 10 = 10 Marks)

Q1. Which of the following is the basic unit of heredity?

Answer: Gene. The gene is the basic physical and functional unit of heredity made up of DNA.

Q2. In which organ of the human body does fertilization occur?

Answer: Fallopian tube (oviduct). The fusion of male and female gametes occurs in the ampulla region of the fallopian tube.

Q3. Which pigment is responsible for capturing light energy in photosynthesis?

Answer: Chlorophyll. Specifically, chlorophyll-a is the primary photosynthetic pigment.

Q4. What is the full form of AIDS?

Answer: Acquired Immuno Deficiency Syndrome. It is caused by the Human Immunodeficiency Virus (HIV).

Q5. Which organelle is known as the powerhouse of the cell?

Answer: Mitochondria. It produces ATP through cellular respiration.

Q6. Who proposed the theory of natural selection?

Answer: Charles Darwin. He proposed the theory in his book ‘On the Origin of Species’ in 1859.

Q7. Which hormone regulates blood sugar levels?

Answer: Insulin. It is produced by the beta cells of the pancreas and lowers blood glucose levels.

Q8. What is the function of the root hair in plants?

Answer: Absorption of water and minerals from the soil through the process of osmosis.

Q9. Which vitamin is produced in the skin when exposed to sunlight?

Answer: Vitamin D (cholecalciferol). It is essential for calcium absorption and bone health.

Q10. Which enzyme is used to cut DNA at specific sites in biotechnology?

Answer: Restriction endonuclease. It cuts DNA at specific recognition sequences called restriction sites.

📝 Section B: Very Short Answer (2 × 5 = 10 Marks)

Q11. What is DNA replication? Where does it occur?

Answer: DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. It occurs in the nucleus during the S-phase of the cell cycle. The process is semi-conservative and is carried out by enzymes including DNA polymerase and helicase.

Q12. State Mendel’s Law of Segregation.

Answer: The Law of Segregation states that during gamete formation, the two alleles for a trait separate from each other so that each gamete carries only one allele for each gene. This happens during the first division of meiosis (anaphase I).

Q13. What is the function of an ecosystem’s decomposers?

Answer: Decomposers (bacteria, fungi) break down dead organic matter into simpler inorganic substances, releasing nutrients back into the environment. They play a crucial role in nutrient cycling and maintaining ecosystem balance.

Q14. Define biodiversity.

Answer: Biodiversity refers to the variety of life forms on Earth, including diversity within species (genetic diversity), between species (species diversity), and of ecosystems (ecological diversity).

Q15. What is the function of the ozone layer?

Answer: The ozone layer in the stratosphere absorbs most of the Sun’s harmful ultraviolet (UV-B) radiation, protecting living organisms from its damaging effects like skin cancer, cataracts, and DNA damage.

✍️ Section C: Short Answer (3 × 10 = 30 Marks)

Q16. Explain the process of photosynthesis with a chemical equation.

Answer: Photosynthesis is the process by which green plants convert light energy into chemical energy. It occurs in chloroplasts.

Chemical Equation:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Stages:

• Light Reaction: Occurs in thylakoid membranes. Chlorophyll absorbs light, splitting water (photolysis) to release O₂, and producing ATP and NADPH.
• Dark Reaction (Calvin Cycle): Occurs in the stroma. CO₂ is fixed into glucose using ATP and NADPH produced in the light reaction.

Q17. Describe the structure of the human heart.

Answer: The human heart is a four-chambered muscular organ located in the thoracic cavity.

• Chambers: Two atria (upper) and two ventricles (lower)
• Valves: Tricuspid (right AV), Bicuspid/Mitral (left AV), Pulmonary (right ventricle→pulmonary artery), Aortic (left ventricle→aorta)
• Function: Pumps oxygenated blood from lungs to body (left side) and deoxygenated blood from body to lungs (right side)

Q18. What is DNA fingerprinting? List its applications.

Answer: DNA fingerprinting is a technique to identify individuals by analyzing their unique DNA patterns using restriction enzymes and gel electrophoresis.

Applications:

• Forensic science — crime scene investigation
• Paternity testing
• Identifying human remains
• Studying genetic diversity in populations
• Wildlife conservation — tracking poaching

📄 Section D: Long Answer (5 × 4 = 20 Marks)

Q26. Explain the mechanism of protein synthesis (translation) in detail.

Answer: Protein synthesis occurs in the cytoplasm on ribosomes.

Stages:

1. Initiation: mRNA binds to the small ribosomal subunit. Initiation factors help in the binding. The start codon (AUG) is recognized.
2. Elongation: tRNA carrying amino acids enters the A-site of the ribosome. Peptide bonds form between adjacent amino acids via peptidyl transferase. The ribosome moves along mRNA (translocation).
3. Termination: When a stop codon (UAA, UAG, UGA) is reached, release factors cause the polypeptide chain to detach.

The newly formed protein then undergoes folding and modification in the endoplasmic reticulum and Golgi apparatus.

Q27. Describe the immune system of the human body.

Answer: The immune system is the body’s defense mechanism against pathogens.

Types:

• Innate Immunity: Non-specific, present from birth. Includes skin, mucous membranes, phagocytes (neutrophils, macrophages), natural killer cells, and inflammatory response.
• Adaptive Immunity: Specific, develops after exposure. Includes B-cells (produce antibodies) and T-cells (helper T-cells, cytotoxic T-cells). Memory cells provide long-term immunity.

Types of Immunity:

• Active Immunity: Body produces its own antibodies (natural infection or vaccination)
• Passive Immunity: Ready-made antibodies are transferred (mother to fetus, antivenom injection)

📊 Chapter-wise Weightage (2023 Exam)

🎯 Exam Preparation Tips

1. NCERT is mandatory: 90% of questions come directly from NCERT textbook. Read each chapter thoroughly.
2. Practice diagrams: Labeled diagrams carry marks. Practice drawing and labeling all important diagrams.
3. Previous year papers: Solve at least 5 previous years’ papers to understand pattern and time management.
4. Focus on weightage: Chapters 5, 6 (Genetics) and 2, 3 (Reproduction) have highest weightage.
5. Write in points: Answers with bullet points and diagrams score higher in board exams.
6. Terminology matters: Use correct biological terms — this shows conceptual clarity.

❓ FAQs

Q: What is the pass mark for MP Board Class 12 Biology?

A: Minimum 23 marks out of 70 in theory + 13 out of 30 in practicals (total 36 out of 100).

Q: Is NCERT enough for the Biology exam?

A: Yes, NCERT Class 12 Biology textbook is sufficient for 90% of the paper. For extra practice, refer to MP Board previous year question banks.

Q: How many diagrams are asked?

A: At least 2-3 diagram-based questions appear each year (heart, nephron, DNA, and flower structure are common).

Q: How should I prepare the practical exam?

A: Practice all 15 prescribed experiments, spotter identification (10 specimens), and maintain a well-written practical file.

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