Theory:

Food is useful for the survival of the living beings because it serves as a rich source of carbohydrates, proteins, fats, vitamins and minerals required for the supply of energy to carry out necessary life processes, proper growth and development of human body. 
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It is also required for the repair of the damaged body parts and to fight diseases.
The components of food that are necessary for our body are called nutrients.
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Mode of Nutrients: Nutrition is the mode of consumption of food by a living being and its utilization by the body.
There are two different modes of nutrition:
  • Autotrophic mode of nutrition
  • Heterotrophic mode of nutrition
Autotrophic mode of nutrition: Autotrophic mode of nutrition is the living being produces their own food in the presence of simple substances. The organisms undergoing this mode of nutrition are termed as autotrophs (auto meaning self; trophos meaning nourishment).
For example: Plants (Tree bearing fruits)
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Heterotrophic mode of nutrition: Heterotrophic mode of nutrition is the mode of nutrition the living being consumes plants or other animals. The organisms undergoing this mode of nutrition are termed as heterotrophs (heteros meaning another; trophos meaning nourishment).
For example: human beings, and animals (cow eating grass).
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