1. Why is blood called a connective tissue? Blood connects
different parts of the body by transporting nutrients, gases, hormones, and waste. It has cells (RBC, WBC,
Platelets) suspended in a fluid matrix (Plasma), which is a characteristic of connective tissue.
2. What would happen if there were no valves in veins? Blood
would flow backward (away from the heart) due to gravity, especially in the legs. This would cause pooling
of blood, swelling, and circulatory failure. Valves ensure unidirectional flow towards the heart.
3. Why is the rate of photosynthesis low in guard cells?
Guard cells have chloroplasts but their main function is regulating stomatal opening. Their photosynthesis
rate is low because they are specialized for gas exchange control, not food production.
4. Why is the small intestine so long (6-7 meters)? A long
length provides: (a) More time for complete digestion, (b) Larger surface area for absorption. Villi and
microvilli further increase this area to ~250 m² for efficient nutrient absorption.
5. What is dialysis and when is it needed? Dialysis is an
artificial blood-filtering process used when kidneys fail. A dialysis machine has a semipermeable membrane
that removes urea and excess salts from blood while retaining essential substances.
6. Why can't dialysis fully replace kidney function? Kidneys
also produce hormones like Erythropoietin (for RBC production) and regulate blood pressure. Dialysis only
filters blood and cannot perform these endocrine functions. Hence, kidney transplant is preferred for
long-term treatment.
7. How does dialysis fluid work? The dialysis fluid has the
same concentration of glucose and salts as normal blood, but no urea. Urea diffuses from blood (high
concentration) into the fluid (low concentration) across the semipermeable membrane.
8. What causes a heart attack? Blockage in coronary arteries
(which supply blood to heart muscles) due to fat deposits (atherosclerosis). This reduces O₂ supply, causing
heart muscle cells to die.
9. Why is a heart transplant sometimes necessary? If a large
portion of heart muscle dies or the heart is severely weakened, it cannot pump blood effectively. A
transplant replaces the damaged heart with a healthy donor heart.
10. How does an artificial pacemaker help? The heart's
natural pacemaker (SA node) controls heartbeat rhythm. If it fails, an artificial pacemaker generates
electrical impulses to maintain a regular heartbeat, preventing arrhythmias.
11. Assertion: Veins have valves but arteries do not.
Reason: Blood in arteries flows with high pressure (from heart), so no backflow risk. Veins
carry blood at low pressure, and valves prevent backflow, especially in limbs.
Both A and R are True, R is correct explanation of A.
12. Why do desert plants have sunken stomata? Sunken stomata
are located in pits, creating a humid microenvironment that reduces water loss. This is an adaptation for
survival in dry conditions.
