In your junior classes, you have read about various bases on which we differentiate between living and non-living things. You may recall that living beings show movement, respiration, nutrition, growth, etc. These processes are not present in non-living things.
But we are unable to see movement or nutrition or growth or breathing in many living beings. How do we say that such organisms are living beings.
Various movements, which may not be apparent from outside take place inside a living being. These movements can be on the scale of molecules or on the scale of cells.
Living beings need certain processes to replace worn out parts. They need some raw materials for doing that. These raw materials come through food.
Food is further converted into energy so that various movement can take place. So, it can be said that there are certain processes in a living being which are necessary to maintain life. These processes are called life processes
In this section, you will read about different types of nutrition. Depending on the complexity of molecules in food, different living beings follow different modes of nutrition.
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
|Autotrophic Nutrition||Organism makes its own food.|
|Heterotrophic Nutrition||Organism depends on other organisms for food.|
|Saprotrophic Nutrition||Organism feeds on dead remains, and digestion happens before ingestion of food.|
|Holozoic Nutrition||Digestion happens after ingestion of food, i.e. inside the body of the predator.|
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. Since the body of all organisms are made of carbon-based molecules, hence all organisms need food which contain carbon-based molecules. The food is always taken from outside. However, some organisms make food by utilising raw materials which are taken from outside.
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. Carbohydrate is required for generating energy and hence is often consumed in largest proportion. Protein is building block of cells, so protein is necessary for all living beings. Lipid is also an important building block of cell. Minerals and vitamins are required for facilitating various biochemical functions.
Types of Nutrition:
- Autotrophic Nutrition: The mode of nutrition through which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition. These organisms are called photosynthetic because they process raw materials in presence of sunlight to make food. Some organisms process certain raw materials through chemical reactions, without utilising the sunlight. Such organisms are chemosynthetic.
- Heterotrophic Nutrition: The mode of nutrition through which an organism takes food from another organism is called heterotrophic nutrition. Organisms, other than autotrophs, follow heterotrophic mode of nutrition. These organisms directly or indirectly depend on autotrophs for food. For example, almost all the animals directly or indirectly take food from plants. Animals which eat plants are called herbivores, while flesh-eating animals are called carnivores. 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. Digestion involves converting complex molecules into simple molecules so that they can be utilised by the organism. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Saprotrophs feed on dead remains of different organisms. By doing so, they help in decomposition of organic waste. This is an important process during various biogeochemical cycles. Many bacteria and all the fungi follow saprotrophic mode of nutrition.
- Holozoic Nutrition: In holozoic nutrition, the digestion happens inside the body of the organism, i.e. after the food is ingested. Animals and protozoa follow this mode of nutrition. In the next section, you will read how an amoeba (a protozoan) follows holozoic mode of nutrition.