(a) Define a nutrient. Name four important nutrients present in our food.

(b) What are the various types of heterotrophic nutrition ?

(a)
A nutrient can be defined as a substance which an organism obtains from its surroundings and uses it as a source of energy or requiires for the biosynthesis of its body constituents.

Carbohydrates,fats,proteins,minerals,vitamins and water are nutrients.

(b)
There are three types of heterotrophic nutrition. They are

(i) Saprotrophic nutrition
A saprophyte or saprotroph is an organism which gets its energy from dead and decaying organic matter. This may be decaying pieces of plants or animals. We can say that saprophytes are heterotrophs. They are consumers in the food chain. This is the typical life-style of fungi.
(ii) Parasitic nutrition.
This involves living off an organism in the form of a parasite.

(iii) Holozoic nutrition
Holozoic nutrition (Greek: holo-whole ; zoikos-of animals) is a type of heterotrophic nutrition that is characterized by the internalization (ingestion) and internal processing of gaseous, liquids or solid food particles.

Ingestion: In animals, this is merely taking of food through the mouth.