Transportation — Telangana (SSC) Class 10 Science Solutions (Free)

Transportation: Movement of substances (nutrients, gases, hormones, waste) from one part of organism to another. Why transportation is essential in multicellular organisms: 1. Distance: Cells in interior cannot directly access oxygen (lungs) or nutrients (digestive system) • Requires transport from external environment to deep tissues 2. Nutrient distribution: • Digestive system absorbs glucose, amino acids • Blood carries to all cells for energy, growth, repair 3. Oxygen delivery: • Lungs absorb O₂; blood carries to respiring tissues • All cells need O₂ for aerobic respiration 4. Waste removal: • Tissues produce CO₂, urea, other waste • Blood transports to lungs (CO₂), kidneys (urea) for excretion 5. Hormone distribution: • Endocrine glands produce hormones • Blood carries to target organs for regulation 6. Heat distribution: • Metabolic heat from muscles transported to skin → thermoregulation 7. Defense: • White blood cells transported to infection sites

Human circulatory system: Heart (4 chambers): 1. Right atrium: Receives deoxygenated blood from body (via vena cava) 2. Right ventricle: Pumps deoxygenated blood to lungs (via pulmonary artery) 3. Left atrium: Receives oxygenated blood from lungs (via pulmonary vein) 4. Left ventricle: Pumps oxygenated blood to body (via aorta); thickest wall Blood vessels: 1. Arteries: Carry blood AWAY from heart; thick muscular walls; withstand high pressure; no valves 2. Capillaries: Microscopic; site of gas/nutrient exchange; thin walls (one cell); connects arteries to veins 3. Veins: Carry blood TOWARD heart; thin walls; low pressure; have valves to prevent backflow Circulation pattern: Body → vena cava → right atrium → right ventricle → pulmonary artery → lungs Lungs → pulmonary vein → left atrium → left ventricle → aorta → body

Cardiac cycle: One complete sequence of heart contraction and relaxation (~0.8 seconds at 75 bpm) Phases: 1. Atrial systole (0.1 s): Atria contract → blood pushed into ventricles • Ventricles relaxed → filling 2. Ventricular systole (0.3 s): Ventricles contract → blood pushed into arteries • Tricuspid and mitral valves close → 'S1' sound (lubb) • Aortic and pulmonary valves open 3. Ventricular diastole (0.4 s): All chambers relax → blood enters atria • Aortic and pulmonary valves close → 'S2' sound (dupp) • Cycle repeats Heart sounds: 'Lubb-dupp' pattern (S1-S2) • S1 (lubb): Closure of AV valves (tricuspid, mitral) at start of ventricular systole • S2 (dupp): Closure of semilunar valves (aortic, pulmonary) at start of diastole Normal pulse rate: • Resting: 60-100 beats/minute (average 72 bpm) • Athletes: 40-60 bpm (lower due to fitness) • During exercise: Up to 180-200 bpm • Children: 70-100 bpm

Blood pressure (BP): Force exerted by blood on artery walls; measured in mmHg. Recorded as: Systolic/Diastolic • Systolic: Pressure when ventricles contract (maximum) • Diastolic: Pressure when ventricles relax (minimum) Normal blood pressure: • Ideal: 120/80 mmHg • Elevated: 120-129/<80 mmHg • Stage 1 hypertension: 130-139/80-89 mmHg • Stage 2 hypertension: ≥140/≥90 mmHg Causes of high blood pressure (hypertension): 1. Increased cardiac output: Heart pumps more forcefully 2. Increased vessel resistance: Narrowed arteries (due to plaque, atherosclerosis) 3. Increased blood volume: Excess salt retention → water retention 4. Stiffness of arteries: Loss of elasticity with age 5. Risk factors: • Obesity, high salt diet, stress, lack of exercise • Smoking, alcohol, family history • Kidney disease, hormonal imbalances Consequences: Damages heart (heart attack), vessels (stroke), kidneys

Blood composition: 1. Plasma (55% of blood volume): Components: Water (90%), proteins, glucose, ions, hormones, vitamins Functions: Transports nutrients, hormones, waste; maintains osmotic pressure; buffers pH 2. Red blood cells/Erythrocytes (45% of blood volume): • No nucleus (mature mammalian RBCs) • Biconcave disc shape → large surface area • Contains hemoglobin → binds O₂ • Functions: Transport oxygen to tissues; transport some CO₂ • Count: 4.5-5.5 million per mL blood 3. White blood cells/Leukocytes (<1% of blood volume): • Nucleated cells • Types: Neutrophils (phagocytes), lymphocytes (antibodies), monocytes (macrophages) • Function: Defense against pathogens; immunity • Count: 4,500-11,000 per mL blood 4. Platelets/Thrombocytes (<1% of blood volume): • Cell fragments; no nucleus • Function: Blood clotting; wound healing • Count: 150,000-400,000 per mL blood

Transport in plants occurs via vascular tissues: Xylem: Structure: Composed of tracheids and vessels • Vessel elements: Elongated, thick-walled, dead at maturity, arranged end-to-end • Tracheids: Narrow, tapered, closed ends • Lignin present in walls → provides strength • No cell membranes (dead) → continuous lumen Function of xylem: 1. Transport of water from roots to leaves (upward transport only) 2. Transport of minerals dissolved in water 3. Provides mechanical support (lignin) 4. Water rises due to: • Root pressure (osmotic) • Capillary action • Transpiration pull (evaporation from leaves creates tension) Phloem: Structure: Composed of sieve tubes and companion cells • Sieve tube elements: Living, lack nucleus, thin walls • Companion cells: Neighbor sieve tubes, have nucleus, provide ATP • Plasmodesmata connect sieve tube to companion cell Function of phloem: 1. Transport of organic solutes (glucose, amino acids, hormones) - bidirectional 2. Transport from source (leaves) to sink (roots, fruits, growing tissues) 3. Requires energy (ATP) - active transport 4. Living cells allow metabolism Key difference: Xylem = water/minerals upward (dead cells); Phloem = nutrients bidirectional (living cells)

Transpiration: Loss of water vapor from leaves (and stems) through stomata into atmosphere. Process: • Water in leaf cells evaporates → water vapor • Vapor diffuses out through stomata (mainly) • Driven by gradient (inside leaf humid; outside dry) • Increases during day, hot weather, low humidity, wind Translocation: Movement of organic solutes (glucose, amino acids) through phloem from source to sink. Process: • Source: Leaves (photosynthesis produces glucose) • Pathway: Glucose enters sieve tubes via companion cells (active transport) • Osmotic pressure increases in sieve tubes → water enters • Pressure gradient drives solution from source to sink • At sink: Glucose unloaded, water leaves • Requires ATP (energy) Importance of transpiration: 1. Water uptake: Creates tension in xylem → water pulled from roots 2. Mineral transport: Water carries minerals to leaves 3. Cooling: Evaporative cooling prevents leaf overheating 4. Photosynthesis: Keeps leaves hydrated 5. Nutrient distribution (indirectly): Water flow enables nutrient movement Note: Transpiration is necessary evil — water loss unavoidable when stomata open for photosynthesis