Life Processes - Notes (Class 10 Science)
1. Introduction
- Life processes are the basic activities essential for survival of living organisms.
- These include: Nutrition, Respiration, Transportation, Excretion.
- They provide energy, help in growth, repair and reproduction.
- Energy is mainly obtained from food.
- Non-living things do not perform these processes.
2. Nutrition
Definition:
- Process by which organisms obtain and utilize food for energy, growth, and repair.
Need for Nutrition:
- Provides energy for life processes.
- Supplies raw materials for growth and repair.
- Maintains body functions and immunity.
Types of Nutrition:
1. Autotrophic – Organisms prepare their own food from CO₂ and H₂O (plants, some bacteria).
2. Heterotrophic – Organisms depend on others for food (animals, fungi, humans).
Modes of Heterotrophic Nutrition:
- Saprotrophic: Feed on dead and decaying matter (fungi).
- Parasitic: Depend on host for food (tapeworm, Cuscuta).
- Holozoic: Ingestion, digestion, absorption, assimilation, egestion (humans, Amoeba).
NCERT Diagram: Fig 6.1 – Modes of Nutrition
3. Autotrophic Nutrition
Definition:
- Mode of nutrition in which organisms prepare their own food from simple inorganic substances using energy from sunlight.
- Process of preparing food (glucose) from CO₂ and H₂O using sunlight and chlorophyll.
- Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (in presence of sunlight and chlorophyll).
Raw Materials Required:
- CO₂ (from air through stomata)
- Water (from soil via roots)
- Chlorophyll (in chloroplasts)
- Sunlight (energy source)
Events of Photosynthesis:
1. Absorption of light by chlorophyll.
2. Splitting of water (photolysis) → hydrogen, oxygen, electrons.
3. Reduction of CO₂ to carbohydrates using hydrogen and energy.
Factors Affecting Photosynthesis:
- Light intensity, CO₂ concentration, Water, Chlorophyll, Temperature.
Importance:
- Provides food for all organisms.
- Releases O₂ for respiration.
- Maintains balance of O₂ and CO₂ in atmosphere.
NCERT Diagrams:
- Fig 6.2 – Cross-section of a leaf showing chloroplast.
- Fig 6.3 – Pathway of Photosynthesis.
4. Heterotrophic Nutrition
Definition:
- Mode of nutrition in which organisms depend on other organisms for food.
Types:
1. Saprotrophic – Obtains food from dead and decaying matter (fungi, some bacteria).
2. Parasitic – Derives food from a living host and harms it (plasmodium, Cuscuta).
3. Holozoic – Takes in complex food, digests, absorbs, assimilates, and egests it (Amoeba, humans).
Steps in Holozoic Nutrition:
1. Ingestion (taking in food)
2. Digestion (breaking down food into simpler form)
3. Absorption (nutrients absorbed into blood)
4. Assimilation (utilization of absorbed food)
5. Egestion (removal of undigested food)
NCERT Diagram: Fig 6.4 – Nutrition in Amoeba.
5. Nutrition in Unicellular Organisms
Example: Amoeba
- Mode: Holozoic nutrition.
Process in Amoeba:
- Uses pseudopodia to engulf food (phagocytosis).
- Food vacuole forms inside cell.
- Enzymes digest food in vacuole.
- Absorbed food used for energy and growth.
- Undigested food expelled outside.
Example: Paramecium
- Uses cilia to sweep food particles into cell mouth.
NCERT Diagram: Fig 6.4 – Nutrition in Amoeba.
6. Nutrition in Human Beings
Steps:
1. Ingestion – Food taken through mouth.
2. Digestion – Breakdown of food into simpler forms.
Digestive System Organs:
- Mouth: Teeth (chewing), Salivary glands (saliva with amylase breaks starch into sugar).
- Oesophagus: Transfers food to stomach.
- Stomach: Gastric glands → HCl (kills bacteria), Pepsin (digests proteins), mucus (protects lining).
- Small Intestine: Bile from liver emulsifies fats; Pancreatic juice digests proteins, carbohydrates, fats; Intestinal juice completes digestion.
- Large Intestine: Absorbs water, forms feces.
Absorption & Assimilation:
- Small intestine villi absorb nutrients into blood.
- Blood transports nutrients to cells.
- Liver stores glucose as glycogen.
Egestion:
- Removal of undigested food via anus.
NCERT Diagram: Fig 6.5 – Human Digestive System.
7. Respiration
Definition:
- Biochemical process where food (glucose) is broken down to release energy (ATP).
Types:
1. Aerobic Respiration:
- In presence of oxygen.
- Complete breakdown of glucose into CO₂ and H₂O.
- Produces 38 ATP.
Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
2. Anaerobic Respiration:
- In absence of oxygen.
- Partial breakdown of glucose.
- Produces ethanol + CO₂ (yeast) or lactic acid (muscles).
Equation: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + Energy
In humans:
- Breathing → Exchange of gases (O₂ intake, CO₂ out).
- Respiration → Cellular oxidation of food to release energy.
NCERT Diagram: Fig 6.6 – Human Respiratory System.
8. Transportation in Animals
Definition:
- The system by which materials (O₂, CO₂, nutrients, hormones, waste) are transported throughout the body.
Human Transport System:
- Circulatory system = Heart + Blood + Blood vessels.
Functions:
- Transport O₂ from lungs to body cells.
- Transport CO₂ from cells to lungs.
- Transport nutrients, hormones, waste products.
Blood:
- Plasma: Transports nutrients, hormones, waste.
- RBC: Carry oxygen using haemoglobin.
- WBC: Fight infections.
- Platelets: Help in clotting.
NCERT Diagram: Fig 6.7 – Human Circulatory System.
9. Heart
Structure:
- Muscular organ with 4 chambers: Right atrium, Right ventricle, Left atrium, Left ventricle.
- Right side → pumps deoxygenated blood to lungs.
- Left side → pumps oxygenated blood to body.
Working:
- Double circulation (blood passes through heart twice in one cycle):
1. Pulmonary circulation → Heart → Lungs → Heart.
2. Systemic circulation → Heart → Body → Heart.
Importance:
- Maintains constant supply of O₂ and nutrients.
- Removes CO₂ and waste.
NCERT Diagram: Fig 6.8 – Structure of Human Heart.
10. Blood Vessels
Types of Blood Vessels:
1. Arteries:
- Carry oxygenated blood away from heart (except pulmonary artery).
- Thick, elastic walls to bear pressure.
2. Veins:
- Carry deoxygenated blood to heart (except pulmonary vein).
- Thin walls, valves present to prevent backflow.
3. Capillaries:
- Thin-walled, one cell thick.
- Allow exchange
of gases, nutrients, and waste between blood and tissues.
Importance:
- Ensure smooth and regulated flow of blood in the body.
NCERT Diagram: Fig 6.9 – Artery and Vein structure.
