Various functions carried out by living beings; which are necessary to maintain and continue life are called life process. Following are the life processes in living beings:
- Transportation of substances
The process by which an organism takes food and utilizes it is called nutrition.
Need of nutrition: Organisms need 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.
Nutrients: 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.
Types of Nutrition:
- Autotrophic Nutrition: The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.
- Heterotrophic Nutrition: The mode of nutrition in which an organism takes food from another organism is called heterotrophic nutrition. Organisms; other than green plants and blue-green algae follow heterotrophic mode of nutrition. Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.
- Saprophytic Nutrition: In saprophytic nutrition; the organism secretes digestive juices on 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.
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