A nutrient can be defined as a substance which an organism obtains from its surroundings and uses it as a source of energy or for the biosynthesis of its body constituents (like tissues and organs). The four important nutrients present in our food are: carbohydrates, fats, proteins and mineral salts.
Nutrition is of two types namely, autotrophic and heterotrophic mode of nutrition. Plants exhibit autotrophic mode of nutrition. They prepare their own food by the process of photosynthesis. Animals exhibit heterotrophic mode of nutrition. Heterotrophic mode of nutrition can be categorised into holozoic mode, parasitic mode and saprophytic modes of nutrition.
The various types of Heterotrophic nutrition are:
*Holozoic mode of nutrition is the process in which an organism takes in whole food. The food ingested undergoes digestion, absorption and assimilation.
e.g. small organisms like amoeba large organisms like human beings.
*Parasitic mode of nutrition is the process in which organism derives its nourishment from host organisms either in liquid form or nutrient form.
e.g. Taenia solium is the tape worm living in human intestine.
*Saprophytic mode of nutrition is the process in which organism derives its nourishment from dead and decaying matter.
e.g. Fungi are heterotrophs that acquire their nutrients from dead and decaying matter by absorption.
