CBSE Class 11 Biology Chapter-15 Important Questions - Free PDF Download
FAQs on Important Questions for CBSE Class 11 Biology Chapter 15 - Body Fluids and Circulation
1. What are the important topics in CBSE Class 11 Body Fluids and Circulation according to board trends (2025–26)?
Key topics for Body Fluids and Circulation include:
- Composition and functions of blood and lymph
- Structure of the human heart
- Double circulation mechanism
- Types and functions of blood vessels
- Blood groups and transfusion
- Blood coagulation and related disorders
- Regulation of cardiac activity
2. Which 5-mark question patterns are frequently asked in Body Fluids and Circulation for Class 11 exams?
Expected 5-mark questions include:
- Explain the structure and working of the human heart with a diagram (2025–26).
- Describe double circulation and its significance in humans.
- Compare open and closed circulatory systems with examples.
- Describe the process and factors involved in coagulation of blood.
- Discuss the regulation of cardiac activity and how neural and hormonal mechanisms coordinate it.
3. How does the double circulation system prevent mixing of oxygenated and deoxygenated blood in humans?
- Human heart has four chambers separated by septa, ensuring oxygenated and deoxygenated blood stay apart.
- The right side receives deoxygenated blood from the body and sends it to the lungs (pulmonary circulation).
- The left side receives oxygenated blood from the lungs and pumps it to the body (systemic circulation).
- Valves prevent backflow, guaranteeing no mixing occurs under normal conditions. This is an essential FUQ for CBSE exams.
4. Why is the left ventricle wall thicker than the right ventricle in the human heart? (Application-based FUQ)
- The left ventricle pumps oxygenated blood to the entire body, which requires more force and higher pressure.
- This demand is met by a thicker muscular wall, compared to the right ventricle which only pumps blood to the nearby lungs.
- This adaptation ensures efficient and sustained systemic circulation.
5. What is the role of lymph in body fluid circulation according to the 2025–26 CBSE syllabus?
- Lymph returns interstitial fluid and proteins to the bloodstream, preventing tissue swelling.
- It aids in the transport of fats from the digestive tract (via lacteals) and provides immune defense via lymphocytes.
- Acts as a supplementary circulatory system, especially important when venous return is obstructed.
6. List and explain two common misconceptions students have about blood circulation in the heart. (HOTS/FUQ)
- Misconception 1: "Blood mixes in the heart's ventricles." — CBSE expects the understanding that septa and valves prevent mixing.
- Misconception 2: "Both atria contract independently." — In reality, both atria contract simultaneously, followed by simultaneous ventricular contraction.
7. How is cardiac output calculated and what factors influence it in CBSE Class 11 exams?
- Cardiac output = Stroke volume × Heart rate.
- Stroke volume: Volume of blood pumped per beat (typically ~70 mL).
- Heart rate: Number of beats per minute (typically ~72 bpm).
- Factors: Physical activity, hormonal regulation (e.g., adrenaline), neural input, and health conditions.
8. Distinguish between arteries and veins with reference to CBSE marking schemes.
- Arteries: Carry blood away from the heart, have thick muscular walls, high pressure, and no valves (except pulmonary artery).
- Veins: Carry blood to the heart, have thinner walls, lower pressure, and possess valves to prevent backflow.
9. What are the functions of different types of leucocytes found in blood?
- Neutrophils: Phagocytosis of pathogens (most abundant, ~62%).
- Eosinophils: Combat parasitic infections, mediate allergic responses.
- Basophils: Release histamine, involved in inflammation and allergic responses.
- Lymphocytes: B cells (antibody production), T cells (cell-mediated immunity).
- Monocytes: Differentiate into macrophages, phagocytosis, antigen presentation.
10. What are the main points to remember for 3-mark questions in Body Fluids and Circulation (CBSE 2025–26)?
- Focus on concise definitions (e.g., cardiac cycle, blood components).
- Be able to compare structures (e.g., right vs. left ventricle, arteries vs. veins).
- Mention one diagram or flowchart for clarity if asked in the exam (label essential parts only).
11. Explain the process of blood clotting highlighting key enzymes and steps as per latest exam pattern. (Expected FUQ)
- Platelet activation releases thromboplastin.
- Thromboplastin initiates the conversion of prothrombin (inactive) to thrombin (active) in the presence of Ca2+ ions.
- Thrombin then catalyzes the conversion of fibrinogen to fibrin.
- Fibrin forms a network, trapping blood cells and forming a stable clot.
12. What are some common errors students make when drawing the heart for exams, and how can scoring be maximized? (HOTS/FUQ)
- Omitting valves, septum, or labeling incorrectly—always include atria, ventricles, valves, major vessels (aorta, pulmonary artery/vein, vena cava), and septum.
- Not showing direction of blood flow—use arrows for clarity.
- Tip: Outline key features first and label clearly for full marks in CBSE boards.
13. Why does swelling occur in the feet when a person stands still for long (application FUQ)?
- Lack of muscle movement reduces venous and lymphatic return from the lower limbs.
- Blood and interstitial fluid accumulate due to gravity, resulting in swelling (edema).
- Moving or flexing the legs helps muscle contractions push fluid back to the heart.











