It is the method of obtaining nutrients from the environment. It can be defined as the process by which the organism ingests, digests, absorbs, transports and utilises nutrients and disposes off their end products.


    The different component of food that have distinct functions like providing energy. materials for body building, maintenance & regulation of metabolism are called nutrient.
    For exmple-Proteins, Minerals, Vitamin, Carbohydrates, fats.

Modes of Nutrition

    (a) Autotrophic Nutrition
    In this type of nutrition, organisms synthesise the organic materials they require from inorganic sources. All green plants are autotrophic and use light as a source of energy for the synthesis.

    The organisms which make their own food from carbon dioxide and water in the presence of sunlight and chlorophyll are called autotrophs. These organisms are also called producers and include green plants and some bacteria.

    It is the process by which green parts of the plant synthesise organic food in the form of carbohydrates from CO2 and water in the presence of sunlight.
    In plants and most algae it occurs in the chloroplasts and there are two principal reactions: 
    (i)    Light reaction (light-dependent) requires the presence of light energy from sunlight which is obtained by photosynthetic pigments, i.e., chlorophyll and used to bring about the photolysis of water.

    (ii)    Dark reaction (light-independent) i.e., this reaction is not dependent on light and during this reaction carbon dioxide is reduced to carbohydrate in a metabolic pathway known as the Calvin cycle.
Difference between light and dark reactions

Various Components of Photosynthesis

    Various components necessary for the process of photosynthesis are :
    2. Carbon dioxide    
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