HUMAN BIOLOGY AND HEALTH: NUTRITION

The sum total processes of taking in, digestion, absorption, and assimilation of food are known as nutrition. It is important because-
(i) it provides energy to the body to perform various activities,
(ii) it provides essential materials for growth,
(iii) it maintains the body temperature.

Types of Nutrition
There are two main types of nutrition:
(a)Autotrophic or holophytic nutrition: It is the process by which organisms can synthesize their food by process of photosynthesis. It is found in green plants. The green plants possess chlorophyll pigment. It helps plants to trap solar energy and manufacture the food (in form of simple sugar) by utilizing simple inorganic materials of nature . Such organisms are known as autotrophs.

(b)Heterotrophic nutrition: It is the process by which organisms cannot synthesis their food by themselves. They are dependent on autotrophs directly or indirectly. They are found in all animals and non-green plants like fungi and bacteria.Such organisms are known as heterotrophs . Depending upon the mode of feeding, there are three types of heterotrophic nutrition:
(i) Holozoic nutrition- organisms like man depend on solid food materials.
(ii) Saprozoic nutrition- organisms like fungi, some bacteria, etc.
(iii) Parasitic nutrition- organisms like Ascaris, tapeworm, etc. depend either or completely on their hosts. They are called parasites.

Nutritional Requirements
Before discussing the digestive system, it is necessary to have an understanding of the body regarding nutrition i.e. the dietary constituents and their functions within the body.

Food and Nutrients- Food can be defined as any essential substance that when absorbed into the body tissues, yields material for the production of energy, growth and repair of tissues and regulation of life processes.

Functions of food