Life process

Biology Doubts

About life process

All the plants and animals [Including human beings] are alive or living. The characteristics of living things are as follows: 

(1) Living things can move by themselves.

(2) Living things can grow.

(3) Living things need food, air and water.

(4) Living things can respond to changes around them. They are sensitive 

(5) Living things respire, excrete and reproduce. 

The basic functions performed by living organisms to maintain their life on this earth are called life processes. The basic life processes common to all the living organisms are: Nutrition, Respiration, Transport, Excretion, Control and Coordination, Growth, Movement and Reproduction. 

Types of Life process

Nutrition Process

Nutrition Process of obtaining food from the surroundings and using it for various metabolic activities by an organism.

(a)Steps of photosynthesis: During the process of photosynthesis, the following events occur :

Absorption of light energy by chlorophyll.

Conversion of light energy to chemical energy and splitting of water molecules into Hydrogen and oxygen.

The above processes are considered as light reaction.

Reduction of carbon-dioxide to carbohydrates. This is also known as dark reaction.

(b)Conditions necessary for photosynthesis:





These conditions are needed for autotrophic mode of nutrition.

(c)Site of photosynthesis: Chloroplast (chlorophyll) containing organelles (i.e. plastid) which are found in large numbers in plant and algal cells undergoing photosynthesis are called chloroplast.

 Digestion in Human Beings

Summary of Digestive enzymes of various glands with their secretion and end products of 

Digestion in Man



1. Animal performs respiration as a single unit. All parts of plant (like root, stem, leaves) perform respiration individually.

2. Respiratory gases are usually transported to long distances. There is little transport of respiratory gases from one part of the plant to other.

3. Respiration occurs at faster rate. It occurs at slower rate.

Respiration involves: 


Gaseous exchange: Breathing   

Breakdown of simple food: Cellular respiration 

 Mechanism of Breathing

Mechanism of breathing involves two phases. 

Inspiration (Inhalation): It is the process by which fresh atmospheric air enter into the lungs (alveoli) via respiratory tract. The diaphragm contracts and becomes flat expanding the chest cavity. The intercostal muscles contract, ribs coming outwards. This further enlarges the chest cavity, lowering the pressure inside lungs. Therefore air rushes in.

Expiration (exhalation): It is the process by which foul air is expelled out of the lungs. The diaphragm relaxes and coming in its normal arched position, compressing the lungs. Intercostal muscles relax and move inwards. This reduces the volume of chest cavity which is already full of air. This forces the air out.

Aerobic and Anaerobic Respiration

1. Takes place in presence of oxygen. Takes place in absence of oxygen.

2. Complete breakdown of food takes place. Partial breakdown of food takes place.

3. Food gets converted into CO2 and water. Food can be converted into either ethanol and CO2 (as in yeast) or in lactic acid (as in animal muscles).

4. 38 molecules of ATP are produced. 2 molecules of ATP are produced.




Circulatory system (Blood and Lymphatic System)

(i) Organ – Heart

(ii) Vessels – Artery, Vein and Capillaries

(iii) Connective tissues (fluid) – Blood and Lymph

Heart (Four chambered)  Blood

Right and Left Atrium

Right and Left Ventricles (i) WBC – fight against diseases

(ii) RBC – carry respiratory gases

(iii) Platelets – clotting of blood

(iv) Plasma – medium (fluid)

 Mechanism of Double Circulation

As the blood passes twice through the heart in one complete cycle in man, it is called double circulation.


It is the biological process of elimination of harmful metabolic waste products from the body of an organism.

Organism Excretory organ

Sponges Osculum

Earthworm Nephridia

Insects Malpighian tubule

Humans Kidneys, lungs and skin

Excretion in humans

Human excretory system consists of:

Kidneys (a pair)

Ureters (a pair)

Urinary bladder


Life process

Life process

Life process

Life process

Life process

Life process

Life process

Life process

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