NCERT Notes of Biology Class 10 Life Processes

NCERT Notes of Biology Class 10 Life Processes

Life processes

The process of basic functions performed by living organisms for their survival and body maintenance. This process is known as life processes. Life processes includes Nutrition, Respiration, Transportation, Excretion, etc.


Nutrition is the process by which an organism obtains nutrients from food and utilises them to obtain energy, building and repairing of their tissues.

Modes of Nutrition

There are two modes of nutrition: autotrophic and heterotrophic.


Nutrients are defined as the substances required for proper growth and maintenance of a living body, i.e. these are materials, which provide energy to an organism.


Those organisms which can prepare their own food with the process of photosynthesis by using raw materials like carbon dioxide from air, sunlight and water is known as autotrophs. e.g. green plants, some bacteria.

Autotrophic mode of nutrition

The mode of nutrition by which an autotrophs makes their own food is known as autotropic mode of nutrition.


Photosynthesis is the process by which green plants make their own food with the help of carbon dioxide and water in the presence of chlorophyll and sunlight. Raw materials for photosynthesis are carbon dioxide and water.


Chloroplast contain a green colour pigment. This pigment is known as chlorophyll.

Main Events of Photosynthesis :

*Absorption of light energy by chlorophyll.

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

*Reduction of carbon dioxide to form carbohydrates.


Stomata are tiny pores present on the surface of the leaves. Exchange of gases and transpiration takes place through stomata.

Guard Cells

The opening and closing of stomata is a function of the guard cells.


Those organisms which cannot prepare their own organic food and fully dependent on autotrops is known as heterotrophs. e.g. animals, human beings, etc.

Heterotrophic mode of nutrition

In heterotrophic mode of nutrition, organisms cannot prepare food on their own. Heterotrophs obtain energy from organic molecules already produced by the autotrophs.

Types of heterotrophic nutrition

Heterotrophic Nutrition is of three types : –

*Holozoic ( e.g. Amoeba, animals ),

*Saprophytic ( e.g. fungi ) and

*Parasitic ( e.g. Cuscuta, ticks and mites ).

Human Digestive System

Human digestive system consists of alimentary canal, i.e. a tube-like structure consisting of mouth, pharynx, oesophagus, stomach, small intestine and large intestine.


Digestion is the process by which complex and large components of food are broken down into simpler forms. These simpler forms are further taken up by different parts of the body and that are finally absorbed.

Alimentary Canal

The human digestive system constitutes a long tubular structure. That long tubular structure is known as the alimentary canal.


Mouth is the first part of digestive system.


Oesophagus or the food pipe helps in the transfer of food down to the stomach.


Stomach is J-shaped organ which stores and partially digest the food entering through the food pipe.


Intestine is the main organ of digestion and absorption. Small intestine is longer in length compared to large intestine.


Anus is the end point of the alimentary canal from where the waste is removed out from the body.

Digestive Glands

Digeative glands are the salivary, gastric intestinal glands along with pancreas and liver.

Salivary Glands

Salivary glands secrete saliva containing salivary amylase which helps in the digestion of starch.

Gastric Glands

Gastric glands is present in the stomach which secrete digestive juice containing pepsin, HCL and mucus.

Intestinal Glands

Intestinal glands present in the walls of small intestine which secrete intestinal juice containing amylolytic, proteolytic and lipolytic enzymes.


Liver is the largest gland of our body and it secretes bile juice for emulsification of fats.


Pancreas secretes pancreatic juice containing trypsin, amylase and lipase enzyme.

Process of Digestion

The process of digestion in all involves ingestion, i.e. intake of food by mouth, digestion, absorption, i.e. passage of digested food from alimentary canal to blood, assimilation, i.e. distribution of digested food to cells of the body and egestion, i.e. the elimination of undigested food ( waste ) from the body.


Respiration is the process by which food taken through nutrition gets oxidised and release energy for performing various activities.

Modes of Respiration

There are two modes of respiration. These are :-

*Aerobic Respiration

*Anaerobic Respiration

*Aerobic Respiration

Aerobic respiration is the complete breakdown of food in the presence of oxygen. It releases large amount of energy in the form of ATP molecules.


ATP stands for Adenosine Triphosphat, which is also known as the energy currency of every cell.

Anaerobic Respiration

Anaerobic respiration is incomplete breakdown of food occurring in the absence of oxygen. It releases small amount of energy. lt can be alcoholic fermentation, i.e. sugar breaks into ethanol and carbon dioxide, and lactic acid fermentation, i,e. sugar breaks into lactic acid.

*Exchange of gases in plants

The energy produced in plants by respiration is utilised in growth and life functions.

**In Leaves

In leaves occurs through diffusion of oxygen through stomata into the cells of the leaf.

**In Rooots

In roots occcurs by diffusion from air present in soil particles to the roots.

**In Stems

In stems occurs through small pores present in the stems called lenticells.

*Exchange of Gases in Animals

Exchange of gases in animals may occur through their skin or through specific respiratory organs. These organs have structures that increase the surface area and are in contact with oxygen rich atmosphere.

** In Aquatic Organisms

The rate of breathing is higher as these organisms utilise oxygen dissolved in water which is present in lesser amount compared to others. Respiration occurs through gills and body surface.

** In Terrestrial Organisms

These organisms use atmospheric oxygen for respiration.

*Human Respiratory System

Respiratory system in human beings serves to provide fresh oxygen to all body cells and removes harmful carbon dioxide from the body.

*Parts and Functions of The Human Respiratory System :-

**Nostrils and Nasal Passage

Nostrils and nasal passage initiate the process of respiration by breathing in the air.


Nasal chamber opens into pharynx. It passes air to the larynx.


Larynx is located n neck, which helps in sound production. Larynx is also known as sound box.


A non-collapsible air conducting tube, exhibit to presence of incomplete rings of cartilages; which also helps keep it open. Trachea is also known as windpipe.

**Bronchi and Bronchioles

Bronchi and bronchioles are the branches into which trachea further divides. Bronchioles are formed by repeated branching of bronchi.


Alveoli are the functional units of kidney. These provide surrface area for gaseous exchange in humans.


Lungs are the primary oprgans for respiration, present in the thoracic cavity.


Ribs are 12 pairs of bones, which helps in respiration by movement of intercoastal muscles attached to them.


Diaphragm is a muscular partition between thorax and abdomen. It forms the base of chest cavity and helps in breathing.

Gaseous exchange in Humans

Oxygen is absorbed via inhalation. Exchange of oxygen and carbon dioxide occurs between blood and alveoli. Carbon dioxide is exhaled through lungs, i.e. exhalation and oxygen is assimilated in the body.


Transportation is the life process of movement of biologically important substances or self from one part of the body to other. Human Circulatory System –

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