Life Processes in Living Organisms

Overview

Key life processes in living organisms: Nutrition, Respiration, Transportation, and Excretion.
Focus on definitions, mechanisms, and exam-oriented details.

Nutrition: How organisms get and use food for energy.
Types:
- Autotrophic: Make own food (e.g., plants via photosynthesis).
- Heterotrophic: Depend on others (Holozoic—humans, Amoeba; Saprophytic—fungi; Parasitic—leeches, cascuta).
Photosynthesis: 6CO₂ + 6H₂O --(sunlight/chlorophyll)--> C₆H₁₂O₆ + 6O₂.
- Occurs in chloroplasts (leaves); chlorophyll is essential.
- Stomata (pores) on leaves allow gas exchange, controlled by guard cells.
Plants store food as starch; animals as glycogen.
Key activities:
- Variegated leaf experiment: Blue-black color with iodine only in green (chlorophyll) areas—proves chlorophyll is needed.
- Bell jar experiment: No starch formed without CO₂—proves CO₂ is essential.

Amoeba: Uses pseudopodia to engulf food, forms food vacuole.
Paramecium: Uses cilia to direct food to food vacuole.
Difference: Amoeba—pseudopodia, variable shape; Paramecium—cilia, fixed slipper shape.

Digestion starts in mouth (teeth, tongue, saliva with amylase for starch).
Food moves via esophagus (peristalsis) to stomach.
Stomach: Gastric juice (HCl—acidic, pepsin—digests protein, mucus—protects lining).
Small intestine: Main site for digestion/absorption; receives bile (liver, emulsifies fat, neutralizes acid) and pancreatic juice (trypsin—protein, lipase—fat).
End products: Proteins → amino acids; Carbs → glucose; Fats → fatty acids/glycerol.
Absorption by villi (finger-like projections with blood vessels).

Respiration: Chemical process releasing energy (ATP) from food (mainly glucose).
Aerobic (with O₂): In mitochondria, produces CO₂, H₂O, energy.
Anaerobic (without/less O₂): In yeast—alcohol + CO₂; in muscles—lactic acid (causes cramps), less energy.
Breathing is physical; respiration is chemical.
In plants: Day—photosynthesis (O₂ out), night—only respiration (CO₂ out).
Fish: Use gills to absorb dissolved O₂ from water.

Air path: Nostrils → nasal passage (filters) → pharynx (common path) → larynx (voice box) → trachea (cartilage rings) → bronchi → bronchioles → alveoli.
Alveoli: Thin-walled, richly supplied with blood vessels; site of O₂/CO₂ exchange.
Diaphragm: Contracts (inhalation, chest expands), relaxes (exhalation, chest contracts).
Residual volume: Some air always remains in lungs for continuous gas exchange.

Components: Blood, blood vessels (arteries, veins, capillaries), heart.
Blood: Plasma (transports CO₂, food, waste), RBCs (O₂ via hemoglobin), WBCs (immunity), platelets (clotting).
Arteries: Carry blood away from heart, thick walls, high pressure, no valves, usually oxygenated.
Veins: Carry blood to heart, thin walls, valves, usually deoxygenated.
Capillaries: Connect arteries and veins, thin walls for exchange.

Four chambers: Right/left atrium (upper), right/left ventricle (lower), separated by septum.
Double circulation: Blood passes through heart twice per cycle (pulmonary and systemic).
Pulmonary artery: Carries deoxygenated blood to lungs (exception).
Pulmonary vein: Carries oxygenated blood to heart (exception).
Four chambers prevent mixing of oxygenated and deoxygenated blood.

Xylem: Transports water/minerals from roots upward (unidirectional, passive).
Phloem: Transports food (bi-directional, needs energy).
Water movement: Root pressure (osmotic), transpiration pull (evaporation from leaves).
Translocation: Food movement via phloem to roots, fruits, growing parts.

Excretion: Removal of nitrogenous wastes (urea, uric acid).
Human excretory organs: Kidneys (filter blood), ureters (to bladder), urinary bladder (stores urine), urethra (expels urine).
Nephron: Kidney’s unit; steps—glomerular filtration, selective reabsorption, tubular secretion.
Artificial kidney (dialysis): Removes waste, no selective reabsorption.
Plant excretion: Gases via stomata, water via transpiration, some waste into soil, leaf fall.