What is nutrition? Explain heterotrophic nutrition with their types.

Nutrition is the process of intake of nutrients from which organisms can derive energy for various life processes.
$\bullet$ 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.
$\bullet$ Heterotrophic nutrition is further divided into three types depending on how the organisms derive their food.
$1$. Saprophytic nutrition:
$\bullet$ Organisms derive their nutrition from dead and decaying organic matter.
$\bullet$ They absorb nutrients through their body wall.
$\bullet$ The organisms depend entirely on non-living substances as a source of food.
$\bullet$ Bacteria and fungi are examples of organisms that follow saprophytic nutrition.
$2$. Parasitic nutrition
$\bullet$ Organisms depend on other living organisms for their nutrition.
$\bullet$ 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.
$\bullet$ Examples of parasitic organisms are several bacteria, fungi, plants (e.g. Cuscuta) and animals (e.g. tapeworm, Ascaris).
$3$. Holozoic nutrition:
$\bullet$ 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.
$\bullet$ Amoeba is an organism which shows the holozoic mode of nutrition.