Learning Objectives
- Understand nutrition in autotrophs and heterotrophs
- Learn the process of photosynthesis
- Understand human digestive, respiratory, circulatory, and excretory systems
- Compare life processes in plants and animals
Key Concepts
Nutrition
Autotrophic nutrition: Organisms make their own food. Green plants perform photosynthesis:
6CO₂ + 6H₂O + Light energy → C₆H₁₂O₆ + 6O₂ (in presence of chlorophyll)
Steps: (i) Absorption of light by chlorophyll (ii) Conversion of light energy to chemical energy and splitting of water (iii) Reduction of CO₂ to carbohydrates.
Heterotrophic nutrition: Organisms depend on others for food. Types: Saprophytic, parasitic, and holozoic.
Human Digestive System
Mouth (saliva + amylase breaks starch) → Oesophagus (peristalsis) → Stomach (HCl + pepsin breaks proteins) → Small intestine (bile from liver emulsifies fats; pancreatic enzymes: trypsin, lipase, amylase; intestinal juice completes digestion; absorption of nutrients through villi) → Large intestine (absorbs water) → Anus.
Respiration
Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP). Occurs in mitochondria.
Anaerobic respiration: In absence of O₂. In yeast: glucose → ethanol + CO₂. In muscles: glucose → lactic acid.
Human respiratory system: Nostrils → Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli (gas exchange through thin walls, rich blood supply, large surface area).
Transportation
In humans: Blood circulatory system with double circulation (pulmonary and systemic). Heart has 4 chambers (2 atria, 2 ventricles). Arteries carry oxygenated blood away from heart (except pulmonary artery); veins carry deoxygenated blood toward heart (except pulmonary vein).
Blood components: Plasma, RBCs (carry O₂ via haemoglobin), WBCs (immunity), platelets (clotting).
In plants: Xylem transports water and minerals upward (transpiration pull). Phloem transports food (sucrose) from leaves to other parts (translocation).
Excretion
In humans: Kidneys filter blood. Each kidney contains millions of nephrons (basic filtration unit). Process: Glomerular filtration → Selective reabsorption → Urine formation → Ureter → Bladder → Urethra.
In plants: Excess water removed through transpiration. Waste products stored in cellular vacuoles, leaves (shed), or as resins and gums.
Summary
Life processes are essential functions for survival: nutrition, respiration, transportation, and excretion. Plants use photosynthesis for autotrophic nutrition. Humans have specialised organ systems for digestion, gas exchange, circulation, and waste removal. These processes work together to maintain homeostasis.
Important Terms
- Photosynthesis
- Process by which green plants convert CO₂ and H₂O into glucose using sunlight
- Peristalsis
- Rhythmic contraction of muscles to push food through the alimentary canal
- Alveoli
- Tiny air sacs in the lungs where gas exchange occurs
- Nephron
- The basic structural and functional unit of the kidney
- Translocation
- Transport of food in phloem from leaves to other parts of the plant
Quick Revision
- Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (chlorophyll + light)
- Aerobic respiration occurs in mitochondria; anaerobic does not require O₂
- Heart has 4 chambers; double circulation prevents mixing of oxygenated and deoxygenated blood
- Xylem carries water upward; Phloem carries food (translocation)
- Nephron is the functional unit of kidney; urine = water + urea + waste salts