Life processes are the basic activities performed by living organisms to maintain life.
The main life processes are:
Nutrition: Obtaining and using food.
Respiration: Releasing energy from food.
Transportation: Carrying materials throughout the body.
Excretion: Removing harmful metabolic wastes.
Nutrition is the process by which organisms obtain food and use it for energy, growth, repair, and maintenance.
Autotrophic nutrition: Organisms such as green plants make their own food.
Heterotrophic nutrition: Organisms such as humans depend on other organisms for food.
Photosynthesis is the process by which green plants prepare food using sunlight, carbon dioxide, and water in the presence of chlorophyll.
Word equation:
Carbon dioxide + Water → Glucose + Oxygen
Chemical equation:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in the presence of sunlight and chlorophyll)
Stomata are small pores mainly present on leaves. They allow exchange of gases and help in transpiration. Each stoma is surrounded by two guard cells.
Human nutrition is holozoic and includes:
Ingestion
Digestion
Absorption
Assimilation
Egestion
The alimentary canal consists of the mouth, oesophagus, stomach, small intestine, large intestine, rectum, and anus. Digestive glands include the salivary glands, gastric glands, liver, pancreas, and intestinal glands.
Mouth: Teeth break food into smaller pieces. Salivary amylase begins starch digestion.
Oesophagus: Moves food by peristalsis.
Stomach: Stores and churns food. Hydrochloric acid creates an acidic medium, pepsin digests proteins, and mucus protects the stomach lining.
Small intestine: Main site of digestion and absorption. Bile emulsifies fats and makes food alkaline. Pancreatic and intestinal enzymes complete digestion.
Villi: Finger-like projections that increase the surface area for absorption.
Large intestine: Absorbs water and forms faeces.
Enzyme | Source | Acts on | Products |
|---|---|---|---|
Salivary amylase | Salivary glands | Starch | Sugars |
Pepsin | Stomach | Proteins | Peptides |
Trypsin | Pancreas | Proteins | Smaller peptides |
Pancreatic amylase | Pancreas | Starch | Sugars |
Lipase | Pancreas and intestine | Fats | Fatty acids and glycerol |
Intestinal enzymes | Small intestine | Carbohydrates, proteins, fats | Glucose, amino acids, fatty acids and glycerol |
Respiration is the process of breaking down food to release energy. The released energy is stored as ATP, the energy currency of the cell.
Glucose is first broken down in the cytoplasm into pyruvate by glycolysis.
Takes place in the presence of oxygen, mainly in mitochondria.
Glucose + Oxygen → Carbon dioxide + Water + Energy
Takes place without oxygen.
In yeast: Glucose → Ethanol + Carbon dioxide + Energy
In muscles: Glucose → Lactic acid + Energy
Lactic acid accumulation can cause muscle cramps.
The pathway is: nostrils → nasal passage → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.
Alveoli are thin-walled, moist structures with a large surface area and rich blood supply. They are the main sites of gas exchange.
Inhalation: Diaphragm contracts and moves downward, ribs move up and out, chest volume increases, and air enters.
Exhalation: Diaphragm relaxes and moves upward, ribs move down and in, chest volume decreases, and air leaves.
The human transport system includes the heart, blood, blood vessels, and lymph.
Plasma transports food, hormones, carbon dioxide, wastes, and salts.
Red blood cells contain haemoglobin and transport oxygen.
White blood cells protect against infections.
Platelets help in blood clotting.
Arteries carry blood away from the heart, have thick elastic walls, and carry blood under high pressure.
Veins carry blood towards the heart, have thin walls and valves, and carry blood under low pressure.
Capillaries are thin vessels that allow exchange between blood and tissues.
The four chambers are the right atrium, right ventricle, left atrium, and left ventricle.
Right atrium receives deoxygenated blood from the body.
Right ventricle pumps it to the lungs through the pulmonary artery.
Left atrium receives oxygenated blood from the lungs.
Left ventricle pumps it to the body through the aorta.
Pulmonary circulation: Right ventricle → lungs → left atrium.
Systemic circulation: Left ventricle → body organs → right atrium.
Double circulation keeps oxygenated and deoxygenated blood separate and provides efficient oxygen supply.
Lymph is a colourless fluid that returns excess tissue fluid to the blood, transports absorbed fats, and supports body defence.
Xylem transports water and minerals from roots to stems and leaves. Root pressure, transpiration pull, cohesion, and adhesion help in water transport.
Transpiration is the loss of water vapour from aerial parts of a plant, mainly through stomata. It cools the plant and creates transpiration pull.
Phloem transports food from leaves to other parts of the plant. This process is called translocation and requires energy. Food can move upward or downward.
Excretion is the removal of harmful metabolic wastes such as carbon dioxide, excess water, nitrogenous wastes, and salts.
It consists of two kidneys, two ureters, a urinary bladder, and a urethra.
Kidneys filter blood and regulate water and salt balance.
Ureters carry urine to the bladder.
The bladder stores urine.
The urethra removes urine from the body.
The nephron is the structural and functional unit of the kidney. It includes the glomerulus, Bowman’s capsule, renal tubule, and collecting duct.
Filtration: Small molecules are filtered from blood in the glomerulus.
Selective reabsorption: Useful substances such as glucose, amino acids, salts, and most water return to the blood.
Tubular secretion: Additional wastes and excess ions enter the tubule.
Urine mainly contains water, urea, uric acid, and excess salts.
If kidneys fail, an artificial kidney removes wastes and excess salts from the blood through dialysis. A kidney transplant may be needed in severe cases.
Plants remove wastes through diffusion, transpiration, storage in leaves, bark, and old xylem, formation of resins and gums, release into soil through roots, and shedding of leaves or bark.
Aerobic | Anaerobic |
|---|---|
Requires oxygen | Does not require oxygen |
Produces carbon dioxide and water | Produces alcohol and carbon dioxide in yeast or lactic acid in muscles |
Releases more energy | Releases less energy |
Arteries | Veins |
|---|---|
Carry blood away from heart | Carry blood towards heart |
Thick, elastic walls | Thin walls |
Narrow lumen | Wide lumen |
Usually no valves | Valves present |
High pressure | Low pressure |
Xylem | Phloem |
|---|---|
Transports water and minerals | Transports food |
Mainly upward movement | Upward and downward movement |
Mostly dead cells | Mostly living cells |
Does not require direct energy | Requires energy |
Diffusion alone is insufficient in multicellular organisms because it is slow and works only over short distances.
The small intestine is suitable for absorption because it is long, coiled, and has villi with thin walls and rich blood supply.
The left ventricle has the thickest wall because it pumps blood to the entire body.
Veins have valves because blood flows through them at low pressure.
Transpiration creates a pull that helps water move upward through xylem.
The nephron is the basic filtration unit of the kidney.
Kidneys remove nitrogenous wastes and regulate water and salt balance.
Nutrition, photosynthesis, chlorophyll, stomata, digestion, peristalsis, villi, respiration, glycolysis, aerobic respiration, anaerobic respiration, alveoli, haemoglobin, double circulation, lymph, xylem, phloem, transpiration, translocation, excretion, nephron, filtration, reabsorption, and dialysis.