Nutrition is the way our body takes in and uses food for health and growth. Nutrients are foods that provide nutrition. Nutrients give us energy, bring growth, help repair body tissues, and regulate body functions. The mode of nutrition varies from one species to another. Broadly, there are two types of nutrition amongst living organisms, namely: Autotrophic mode Heterotrophic mode

The living organism from which a parasite derives its food is called a host. Apart from providing food, host organisms also provide shelter to the parasites. Example-parasitic plant dodder feeds on other plants by attaching themselves to their hosts via a special organ, the haustorium.

Rhizobium is a genus of Gram-negative bacteria, living in symbiotic association in the root nodules of leguminous plants such as peas, beans, etc. It has the ability to fix nitrogen into nitrates. These bacteria obtain carbohydrates from the plant cells and, in return, release nitrate into the plant tissues and the soil.