Introduction to Improvement of food resources

Food is the basic need of all living organisms for their existence. Early man started hunting animals and used fruits and roots of plants to meet his food requirements. Food is required to perform several functions. It is required for growth, development and body repair. It also protects the body from diseases. Food supplies proteins, carbohydrates, fats, vitamins, minerals and water to our body.

It is the combination of various organic and substances which is capable of providing

• energy for the various metabolic activities.
• materials for repair / replacement of worn-out tissues in the body.
• materials for growth & reproduction.
• regulatory substances, body secretions and metabolic activities etc.

Sources of Food: Plants provide us foods like cereals, pulses, oil seeds, fruits and vegetables, on this basis plants are classified as follows :

• Agriculture: (Ager means field ; cultural means cultivation). it is applied biological science which deals with the production of plants raising of animals useful to man, involving soil cultivation, breeding and management of crops and livestock.
• Horticulture: (Hortus-garden ; cultura-cultivation). it is the branch of agriculture and the science of growing vegetables, fruits and ornamental plants.
• Silviculture: (Sylvan-wood and trees) Cultivation of wood and trees e.g. –pine, teakwood, sesamum etc..

Depending upon the mode of obtaining food, organisms are divided into two broad categories, autotrophs and heterotrophs.

Autotrophs are those organisms which make their own food with the help of solar energy from inorganic raw materials like CO ₂ and water. All green plants are autotrophs.

Heterotrophs are those organisms that cannot manufacture their own organic food but obtain the same from outside sources. All animals, human beings and non-green plants are heterotrophs. Heterotrophs obtain their food from biomass of either autotrophs or other heterotrophs which are ultimately dependent upon autotrophs. NCERT solutions for class 9 Science prepared by pw will help you to solve your NCERT text book exercise.