Samacheer Kalvi 10th Science Chapter 14 Short Answer Questions — Transportation in Plants and Circulation in Animals with Answers

Ascent of sap is the upward movement of water and dissolved minerals from the roots to the leaves through xylem vessels.

Forces responsible:

1. Root pressure: Active absorption of minerals by root cells creates osmotic pressure, pushing water upward. Responsible for guttation (water drops at leaf tips).

2. Capillary action: Water rises in narrow xylem tubes due to surface tension — adhesion (water to xylem walls) and cohesion (water to water).

3. Transpiration pull (suction force — main force): Transpiration from leaves creates a negative pressure (suction) that pulls water up through the xylem. The cohesion-tension theory explains this: water molecules stick together (cohesion) and are pulled up as a continuous column by the suction created at the top.

The transpiration pull is the primary and most important force driving water to the tops of tall trees.

Blood is a fluid connective tissue that circulates through the cardiovascular system.

Components:

Functions of blood:

• Transports oxygen from lungs to tissues and CO₂ back
• Distributes nutrients absorbed from gut
• Carries hormones from endocrine glands to target organs
• Maintains body temperature
• Defence against infection (WBCs, antibodies)
• Clotting prevents excessive blood loss

The human heart is a muscular, four-chambered organ located in the thoracic cavity, slightly to the left, enclosed in the pericardium.

Chambers:

• Right atrium: Receives deoxygenated blood from body via superior and inferior vena cava
• Right ventricle: Pumps deoxygenated blood to lungs via pulmonary artery
• Left atrium: Receives oxygenated blood from lungs via pulmonary veins
• Left ventricle: Pumps oxygenated blood to the entire body via aorta (thickest wall)

Valves:

• Tricuspid valve (right AV) — between right atrium and ventricle
• Bicuspid/Mitral valve (left AV) — between left atrium and ventricle
• Semilunar valves — at entrances of pulmonary artery and aorta

Working (one cardiac cycle): 1. Atria contract (atrial systole) → blood flows into ventricles 2. Ventricles contract (ventricular systole) → blood pumped to lungs and body 3. All chambers relax (diastole) → heart fills with blood again 4. Heart rate: ~72 beats per minute

Blood groups are classifications of blood based on the presence or absence of specific antigens (glycoproteins) on the surface of RBCs.

ABO System (discovered by Karl Landsteiner, 1901):

• Group AB = Universal recipient (no antibodies, accepts all)
• Group O = Universal donor (no antigens, no rejection)

Importance: Blood must be matched before transfusion. Mismatched transfusion causes agglutination (clumping) and haemolysis — potentially fatal.

Note: Pulmonary artery is unique — it carries deoxygenated blood (unlike all other arteries). Pulmonary veins are unique — they carry oxygenated blood (unlike all other veins). This is why humans are said to have double circulation — blood passes through the heart twice in each circuit.

Transpiration is the loss of water as water vapour from the aerial parts of a plant, mainly through stomata in leaves.

Types:

• Stomatal transpiration (90%) — through stomata
• Cuticular transpiration — through waxy leaf surface
• Lenticular transpiration — through lenticels in bark

Advantages:

• Creates transpiration pull — drives ascent of sap (water and minerals reach all parts)
• Cools the plant surface (evaporative cooling)
• Helps in mineral absorption from soil
• Maintains turgidity of cells

Disadvantages:

• Excessive water loss causes wilting
• In hot, dry conditions, plants may lose too much water and die
• Plants must close stomata to conserve water, which also limits CO₂ entry needed for photosynthesis

Factors affecting transpiration: Temperature, humidity, wind, light, water availability, leaf area.