Life Processes

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The process by which an organism takes food and utilizes it is called nutrition.

Need of nutrition: Organisms need the energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.

Autotrophic organisms are able to produce organic matter from simple inorganic materials. They consequently create their own food—but require a source of energy to do this.

Autotrophic nutrition is fulfilled by the process by which autotrophs take in CO₂ and H₂O and convert these into carbohydrates in the presence of chlorophyll, sunlight is called Photosynthesis.

6CO₂ + 12H₂O ---> C₆H₁₂O₆ + 6O₂ + 6H₂O

The following process occurs during photosynthesis.

1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
3. Reduction of carbon dioxide to carbohydrates

Heterotrophic nutrition is typical of animals. These organisms eat organic matter in other organisms—either alive (as hunters) or dead (as scavengers).

Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.

Saprophytic Nutrition: In saprophytic nutrition; the organism secretes the digestive juices on the food. The food is digested while it is still to be ingested. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Some insects; like houseflies; also follow this mode of nutrition.

Holozoic Nutrition: In holozoic nutrition; the digestion happens inside the body of the organism, i.e. after the food is ingested. Most of the animals follow this mode of nutrition.

Unicellular/Single-celled organisms: Food is taken up through entire surface.

Example :

1. Amoeba
2. Paramaecium

Paramoecium is also a unicellular organism, the cell has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia which cover the entire surface of the cell.

Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.

A human being is complex animals and has a complex digestive system. The human digestive system is composed of an alimentary canal and some accessory glands.

The alimentary canal is divided into several parts, viz oesophagus, stomach, small intestine, large intestine, rectum and anus.

Salivary gland and pancreas are the accessory glands which lie outside the alimentary canal.

Human body digestive system: