Nutrition is the process of intake of nutrients from which organisms can derive energy for various life processes.
∙ Heterotrophic nutrition is the mode of nutrition in which organisms cannot synthesize their own food and derive nutrition by digesting organic matter from plants and animals.
∙ Heterotrophic nutrition is further divided into three types depending on how the organisms derive their food.
1. Saprophytic nutrition:
∙ Organisms derive their nutrition from dead and decaying organic matter.
∙ They absorb nutrients through their body wall.
∙ The organisms depend entirely on non-living substances as a source of food.
∙ Bacteria and fungi are examples of organisms that follow saprophytic nutrition.
2. Parasitic nutrition
∙ Organisms depend on other living organisms for their nutrition.
∙ The organism on which the parasite feeds and derives its nutrition from is known as the host organism. The host organism is not benefited but is harmed in the association.
∙ Examples of parasitic organisms are several bacteria, fungi, plants (e.g. Cuscuta) and animals (e.g. tapeworm, Ascaris).
3. Holozoic nutrition:
∙ Parts of plants or animals or whole organisms are taken in as food, which is then digested to simple substances and absorbed by cells of the body.
∙ Amoeba is an organism which shows the holozoic mode of nutrition.