Food is needed by all living organisms mainly for growth and repair.
Several organisms need food to maintain body temperature as well.

A variety of substances are taken as food by every organisms from single celluar organisms like amoeba to the complex multicellular organisms like the human body. Even within the human body the cells require a wide variety of substances as food to carryout their functions. The mode of acquiring food varies from organism to organism.

You have studied in the previous classes about how different organisms

get their food. Let us recall them. What are autotrophs? How do autotrophs get their food? What are heterotrophs? How do heterotrophs get their food? Let us study about autotrophic and heterotrophic modes of nutrition and find out why most plants are called as autotrophs.

Autotrophic Nutrition

We know that autotrophs are the organisms capable of using light energy to synthesize chemical compounds.
They acquire nutrients like mineral salts and water from the soil as well as some gases from the air.

They are capable of producing complex compounds like carbohydrates, proteins and lipids from these very simple substances. These compounds produced by autotrophic plants are utilized for providing energy to most of the living organisms and all animals including human beings. Most of the food that we eat are obtained from plants. Even if we depend on animal products, we would find that those animals depend on plants.