Notes Class 10 Science Chapter 5 Life Process

Notes For All Chapters Science Class 10 CBSE

1. Introduction

• Living organisms show movement, growth, and molecular activity.
• Maintenance of life requires continuous molecular movements.
• These include processes like nutrition, respiration, transportation, and excretion.

2. What Are Life Processes?

Life processes: Basic functions essential to maintain life.

Even when at rest, organisms perform life processes to repair and maintain their structure.

Major life processes:

• Nutrition: Intake and use of food.
• Respiration: Release of energy from food.
• Transportation: Movement of materials within the body.
• Excretion: Removal of waste products.

Multi-cellular organisms need specialised systems for these processes.

A transport system distributes food and oxygen.

Waste by-products are removed through excretion.

3. Nutrition

Nutrition: The process of taking in food and using it for growth, repair, and energy.

Two main types:

• Autotrophic Nutrition
• Heterotrophic Nutrition

3.1 Autotrophic Nutrition

Organisms prepare their own food using CO₂, water, sunlight, and chlorophyll.

Process: Photosynthesis

• Converts light energy into chemical energy.
• Carbohydrates formed are used for energy or stored as starch.

Steps of Photosynthesis:

• Absorption of light by chlorophyll.
• Conversion of light energy to chemical energy and splitting of water into hydrogen and oxygen.
• Reduction of CO₂ into carbohydrates.

Stomata allow gas exchange but close to prevent water loss.

Water is absorbed by roots; nutrients like N, P, Fe, Mg are also taken up.

3.2 Heterotrophic Nutrition

Organisms depend on others for food.

Types:

• Saprophytic: Food broken down outside and absorbed (e.g., fungi).
• Holozoic: Ingestion and internal digestion (e.g., animals).
• Parasitic: Derive food from living hosts (e.g., lice, cuscuta).

3.3 Nutrition in Unicellular Organisms

Amoeba: Uses pseudopodia to engulf food, digests in food vacuole.

Paramecium: Uses cilia to move food into a specific ingestion spot.

3.4 Nutrition in Human Beings

• Alimentary canal: Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Anus

Digestive process:

Mouth: Teeth crush food; saliva (amylase) converts starch to sugar.

Oesophagus: Peristalsis moves food to stomach.

Stomach: Gastric glands secrete:

• HCl (acidic medium, kills microbes)
• Pepsin (digests proteins)
• Mucus (protects stomach lining)

Small Intestine: Site of complete digestion.

• Liver secretes bile → emulsifies fats.
• Pancreas secretes enzymes → digest proteins, fats, carbohydrates.
• Intestinal juice → final digestion.
• Villi → absorb digested food into blood.

Large Intestine: Absorbs water, expels waste.

4. Respiration

• Food is oxidised to release energy.
• Types:
  1. Aerobic respiration: In presence of O₂ – complete breakdown → CO₂ + H₂O + energy.
  2. Anaerobic respiration: In absence of O₂ – partial breakdown → alcohol or lactic acid + energy.

Breakdown of glucose:

Glucose → Pyruvate (in cytoplasm)

Pyruvate pathways:

• Yeast: → Ethanol + CO₂
• Muscle cells (low O₂): → Lactic acid
• Mitochondria (O₂ present): → CO₂ + H₂O

ATP (Adenosine Triphosphate):

• Energy currency of the cell.
• Produced during respiration and used for cellular activities.

Respiration in Plants:

• Gaseous exchange by diffusion through stomata and intercellular spaces.

Respiration in Animals:

• Terrestrial: Use oxygen from air.
• Aquatic: Use dissolved oxygen – higher breathing rate.

Human Respiratory System:

• Nostrils → Pharynx → Trachea → Bronchi → Bronchioles → Alveoli
• Alveoli: Gas exchange surface with rich blood supply.
• Haemoglobin: Respiratory pigment carrying oxygen.
• CO₂: Transported dissolved in blood.

5. Transportation

5.1 In Human Beings

Blood: Plasma, RBCs, WBCs, Platelets.

Heart: Pumps blood in a double circulation system:

• Pulmonary circulation: Heart → Lungs → Heart
• Systemic circulation: Heart → Body → Heart

Double Circulation: Ensures oxygenated and deoxygenated blood do not mix.

Blood Vessels:

• Arteries: Carry blood away from heart (high pressure, thick walls).
• Veins: Carry blood to heart (valves prevent backflow).
• Capillaries: Exchange materials with tissues.

Platelets: Help clot blood at injury sites.

Lymph: Colourless fluid, transports fats and drains excess fluid.

5.2 In Plants

• Xylem: Transports water and minerals.
• Phloem: Transports food (translocation).
• Transpiration: Water loss through stomata creates suction for water movement.
• Root Pressure: Pushes water upward at night.
• Translocation: Active transport using ATP.

6. Excretion

6.1 In Human Beings

Excretory system: Kidneys, ureters, urinary bladder, urethra.

Nephron: Functional unit of kidney.

• Filtration occurs in glomerulus and Bowman’s capsule.
• Selective reabsorption of useful substances.
• Urine stored in bladder and excreted via urethra.

Artificial Kidney (Dialysis): Removes nitrogenous waste when kidneys fail.

6.2 In Plants

• Oxygen: Released during photosynthesis.
• Water: Lost by transpiration.
• Waste products: Stored in vacuoles, resins, gums, or excreted into soil.