Class 10 Science

Life Processes: Nutrition

The process by which an organism takes food and utilizes it is called nutrition.

These notes are based on the chapter life processes from class 10 science NCERT book and CBSE syllabus.

  • Need of Nutrition
  • Types of Nutrition
    • Autotrophic Nutrition
    • Heterotrophic Nutrition

Need of nutrition

Organisms need energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.

Since the body of all organisms are made of carbon-based molecules, hence all organisms need food which contain carbon-based molecules. The food is always taken from outside. However, some organisms make food by utilising raw materials which are taken from outside.


Materials which provide nutrition to organisms are called nutrients.

Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.

Carbohydrate is required for generating energy and hence is often consumed in largest proportion. Protein is building block of cells, so protein is necessary for all living beings. Lipid is also an important building block of cell. Minerals and vitamins are required for facilitating various biochemical functions.

Types of Nutrition

There are two types of nutrition: autotrophic and heterotrophic nutrition.

Autotrophic Nutrition

The mode of nutrition through which an organism prepares its own food is called autotrophic nutrition.

Green plants and blue-green algae follow the autotrophic mode of nutrition. These organisms are called photosynthetic because they process raw materials in presence of sunlight to make food.

Some organisms process certain raw materials through chemical reactions, without utilising the sunlight. Such organisms are called chemosynthetic.

Heterotrophic Nutrition

The mode of nutrition through which an organism takes food from another organism is called heterotrophic nutrition. Organisms, other than autotrophs, follow heterotrophic mode of nutrition.

These organisms directly or indirectly depend on autotrophs for food. For example, almost all the animals directly or indirectly take food from plants. Animals which eat plants are called herbivores, while flesh-eating animals are called carnivores. Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.

Saprophytic Nutrition

In saprophytic nutrition, the organism secretes digestive juices on food. The food is digested while it is still to be ingested. Digestion involves converting complex molecules into simple molecules so that they can be utilised by the organism. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Saprotrophs feed on dead remains of different organisms. By doing so, they help in decomposition of organic waste. This is an important process during various biogeochemical cycles. Many bacteria and all the fungi follow saprotrophic mode of nutrition.

Holozoic Nutrition

In holozoic nutrition, the digestion happens inside the body of the organism, i.e. after the food is ingested. Animals and protozoa follow this mode of nutrition. In the next section, you will read how an amoeba (a protozoan) follows holozoic mode of nutrition.

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