Chapter 5: Life Processes

1. Introduction

All living organisms — whether plants, animals, or microorganisms — need energy and raw materials to survive, grow, and reproduce. The processes that together maintain life in living organisms are called Life Processes.

Every organism performs certain basic functions such as nutrition, respiration, transportation, and excretion. These processes ensure that organisms get energy, distribute it, and remove waste products.

Let’s study each life process one by one.

2. Nutrition

 Definition:

Nutrition is the process by which living organisms take in food and use it for various life activities such as growth, energy, and repair.

 Types of Nutrition:
  1. Autotrophic Nutrition
  2. Heterotrophic Nutrition

2.1. Autotrophic Nutrition

  • In this mode, organisms prepare their own food using simple inorganic substances.
  • Green plants, algae, and some bacteria are autotrophs.
  • They make food by the process of Photosynthesis.

Photosynthesis

Definition:

Photosynthesis is the process by which green plants prepare their own food (glucose) using carbon dioxide and water in the presence of sunlight and chlorophyll.

 Equation:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

In words:
 Carbon dioxide + Water → Glucose + Oxygen

 Raw Materials Required:
    1. Carbon dioxide (CO₂) – taken from air through stomata.
    2. Water (H₂O) – absorbed from soil by roots.
    3. Chlorophyll – green pigment in leaves captures light energy.
    4. Sunlight – main source of energy for the process.
 
Steps of Photosynthesis:
    1. Absorption of light energy by chlorophyll.
    2. Conversion of light energy into chemical energy.
    3. Splitting of water molecules into hydrogen and oxygen.
    4. Reduction of CO₂ into carbohydrates using hydrogen.
 
 Factors Affecting Photosynthesis:
    • Light intensity
    • Carbon dioxide concentration
    • Water availability
    • Temperature
 
Importance:
    • It provides food and oxygen to all living beings.
    • It maintains the balance of O₂ and CO₂ in the atmosphere.

2.2. Heterotrophic Nutrition

  • Heterotrophs cannot prepare their own food.
  • They depend on other organisms for nutrition.
Types:
  1. Holozoic Nutrition – Taking solid food (e.g., humans, animals).
  2. Saprophytic Nutrition – Feeding on dead and decaying matter (e.g., fungi).
  3. Parasitic Nutrition – Living on or inside another organism (host) and deriving nutrition (e.g., lice, tapeworm).

1. Nutrition in Humans (Holozoic Nutrition)

The process of taking in food, digesting it, absorbing nutrients, and eliminating waste is called nutrition.

Steps in Human Nutrition:

  1. Ingestion – Taking food into the mouth.
  2. Digestion – Breaking down food into simpler forms.
  3. Absorption – Nutrients absorbed into the bloodstream.
  4. Assimilation – Utilization of absorbed nutrients.
  5. Egestion – Removal of undigested food.

The Human Digestive System

The human digestive system consists of the alimentary canal and digestive glands.

Alimentary Canal Parts:

1. Mouth

    • Food is chewed by teeth.
    • Saliva (from salivary glands) contains amylase enzymes which break starch into sugar.

2. Oesophagus (Food pipe)

    • Carries food to the stomach through peristaltic movement (wave-like muscle contraction).

3. Stomach

    • A muscular bag-like organ.
    • Gastric glands secrete:
      • Hydrochloric acid (HCl) – kills bacteria, provides an acidic medium.
      • Pepsin – digests proteins into peptones.
      • Mucus – protects stomach lining.

4. Small Intestine

    • Long coiled tube (~6 meters).
    • Bile (from liver) – breaks fats into small droplets (emulsification).
    • Pancreatic juice – contains trypsin (for proteins), amylase (for starch), and lipase (for fats).
    • Intestinal juice – completes digestion.
    • Digested food absorbed by villi (tiny finger-like projections) that increase surface area.

5. Large Intestine

    • Absorbs water and minerals.
    • Remaining waste is passed to rectum.

6. Anus

    • Undigested food expelled from body (egestion).

2. Nutrition in Amoeba (Simple Organism)

  • Amoeba is unicellular.
  • It takes food through pseudopodia (false feet).
  • The food is enclosed in a food vacuole.
  • Inside food vacuole, enzymes digest food; then nutrients are absorbed.
  • Waste is removed outside by diffusion.

2. Respiration

Definition:  Respiration is the process by which food is broken down to release energy.
 It involves intake of oxygen and release of carbon dioxide.

Types of Respiration:

1. Aerobic Respiration

    •  Occurs in the presence of oxygen.
    • Glucose → CO₂ + H₂O + Energy
    • Example: Humans, animals, plants.

2. Anaerobic Respiration

    • Occurs in absence of oxygen.
    • Glucose → Alcohol + CO₂ + Energy (in yeast)
    • Glucose → Lactic acid + Energy (in muscles during fatigue)

Cellular Respiration:

It is the process of oxidation of food inside cells to release energy.
 Energy released is stored in ATP (Adenosine Triphosphate) – known as the energy currency of the cell.

Human Respiratory System:

  1. Nostrils – Air enters through nostrils, filtered by hair and mucus.
  2. Pharynx → Larynx → Trachea (windpipe) – Air passes through.
  3. Bronchi – Two branches of trachea leading to each lung.
  4. Bronchioles – Smaller tubes inside lungs.
  5. Alveoli – Tiny air sacs for gas exchange.

Exchange of Gases:

  • O₂ diffuses from alveoli to blood.
  • CO₂ diffuses from blood to alveoli

Mechanism of Breathing

1. Inhalation:

  1. Diaphragm contracts and moves downward.
  2. Lungs expand, air rushes in.

2. Exhalation:

  1. Diaphragm relaxes and moves upward.
  2. Air is pushed out of lungs.

Difference between Breathing and Respiration

Breathing

Respiration

Physical process of air exchange

Chemical process of energy release

Involves lungs

Involves cells

No energy released

Energy released as ATP

3. Transportation

Definition: Transportation is the process by which materials (nutrients, gases, wastes, hormones) are moved to and from different parts of the body.

3.1. Transportation in Human Beings

The human circulatory system consists of:

      • Heart
      • Blood
      • Blood vessels

3.2. The Human Heart

  • Hollow, muscular organ about the size of a fist.
  • Located slightly to the left in the chest cavity.
  • Has four chambers:
      • Right Atrium
      • Right Ventricle
      • Left Atrium
      • Left Ventricle

3.3. Pathway of Blood Circulation:

  1. Deoxygenated blood from body → Right atrium → Right ventricle → Pulmonary artery → Lungs (for oxygenation)
  2. Oxygenated blood from lungs → Pulmonary veins → Left atrium → Left ventricle → Aorta → All body parts

3.4. Blood

  • Plasma – Fluid part carrying nutrients and hormones.
  • RBCs (Red Blood Cells) – Contain haemoglobin, transport oxygen.
  • WBCs (White Blood Cells) – Fight infections.
  • Platelets – Help in blood clotting.

3.5. Blood Vessels

Type

Function

Arteries

Carry oxygenated blood from heart to body

Veins

Carry deoxygenated blood to heart

Capillaries

Connect arteries and veins; exchange of materials

3.6. Lymph

  • Yellowish fluid similar to plasma.
  • Helps in transport of fats and immune functions.

3.7. Transportation in Plants

Plants do not have a circulatory system like animals. They have two main transport tissues:

1. Xylem

    • Transports water and minerals from roots to leaves.
    • Movement is upward.
    • Process called Ascent of Sap

2. Phloem

    • Transports food (sugar) from leaves to other parts.
    • Process called Translocation.

3.8. Transpiration

  • Loss of water vapor from the leaves through stomata.
  • Helps in pulling water upward from roots.

4. Excretion

Definition: Excretion is the process by which waste products of metabolism are removed from the body.

4.1. Excretion in Humans

The human excretory system consists of:

  • Kidneys
  • Ureters
  • Urinary Bladder
  • Urethra

4.2. Structure of Kidney

The human excretory system consists of:

  • Kidneys
  • Ureters
  • Urinary Bladder
  • Urethra

4.3. Nephron – The Functional Unit

Parts:
    1. Bowman’s Capsule – Cup-like structure containing glomerulus (a bunch of capillaries).
    2. Tubule – Reabsorbs useful substances (like glucose, water).
    3. Collecting Duct – Collects urine and sends it to the ureter.

4.4. Steps in Urine Formation:

  1. Filtration – Takes place in Bowman’s capsule.
  2. Reabsorption – Useful substances reabsorbed into blood.
  3. Secretion – Waste materials added to filtrate.
  4. Excretion – Urine passes through ureters → bladder → out through urethra.

4.5. Composition of Urine:

  • Water
  • Urea
  • Uric acid
  • Salts

4.6. Excretion in Plants

Plants also produce waste but in smaller amounts.
 They remove wastes by:

    • Storing them in leaves, fruits, or bark (which later fall off).
    • Releasing gases like CO₂ and O₂ through stomata.
    • Excreting resins, latex, gum

5. Summary of Life Processes

Process

Purpose

Main Organs/Structures

Nutrition

Obtain food and energy

Digestive system

Respiration

Release energy from food

Lungs, cells

Transportation

Circulate materials

Heart, blood, vessels

Excretion

Remove waste

Kidneys, nephron

6. Key Points at a Glance

  • Photosynthesis – Process by which green plants make food using sunlight.
  • Autotrophs make their own food; heterotrophs depend on others.
  • Amoeba takes food using pseudopodia.
  • Human digestion involves mouth, stomach, small intestine, and enzymes.
  • Respiration releases energy stored in food.
  • Heart pumps blood through double circulation.
  • Xylem and Phloem help in plant transport.
  • Nephron is the structural and functional unit of kidney.
  • Excretion removes harmful wastes from body.

7. Important Diagrams (You should practice)

  • Human Digestive System
  • Respiration Pathway in Humans
  • Human Heart and Double Circulation
  • Structure of Nephron
  • Transportation in Plants (Xylem and Phloem)

8. Life Processes – Formula Recap

Process

Equation

Photosynthesis

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Respiration

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

Alcoholic fermentation

Glucose → Alcohol + CO₂ + Energy

9. Summary in Simple Words

Life processes are the activities that keep organisms alive.

  • Plants make their food by photosynthesis.
  • Animals depend on plants or other animals for food.
  • Energy is released through respiration.
  • This energy is used for transport, growth, and reproduction.
  • Waste materials are removed through excretion.

These processes work together to maintain balance in living systems — this is called homeostasis

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