Nutrition In Animals

Animals cannot make food on their own. They depend on plants for their food either directly or indirectly. All organisms including humans require nutrients for the growth, repair, and functioning of the body. They get these nutrients from the digestion of food.

Process of Nutrition In Animals:

There are five steps in the process of Nutrition in animals. These are- Ingestion, Digestion, Absorption, Assimilation, and Egestion.

Nutrition In Animals

a) Ingestion:

The process of taking food, drink, or other substances into the body is called ingestion. Different organisms have different organs for this process. Some of them are mentioned below:

1. Frog: long sticky tongue for catching its prey.                               

2. Paramecium: stiff hair-like projections called cilia for ingestion.

3. Mosquito: proboscis sucks blood.

4. House Fly: feeding tube for sucking up food in solution form.

5. Butterfly: proboscis to suck nectar from flowers.

6. Human: buccal cavity for intaking, chewing, cutting, and swallowing food.


The process of changing insoluble complex food into simple soluble form with the help of different enzymes and other digestive juices in the body is called digestion. There are different organs are found for digestion in different animals. For example, the human digestion process performed in the elementary canal while in unicellular organisms it’s performed in vacuoles. In humans, The food passes through a continuous elementary canal which begins at the buccal cavity and ends at the anus. The canal can be divided into various compartments: (1) the buccal cavity, (2) the esophagus, (3) the stomach, (4) the small intestine, (5) the large intestine ending in the rectum, and (6) the anus. Types of digestive systems in some animals are mentioned in this image-

Types of Digestive systems in different animals

c) Absorption:

The process of absorbing nutrients into the body from digested food through the digestive system is called absorption. By this process, the body gets the required nutrients. There are different types of organs are found in different animals for this process. For example in humans, this process performed in the small intestine, and nutrients absorb into lacteal and blood vessels which are situated in the villi of the small intestine. Once the food particle reaches the bloodstream, they are transported throughout the different parts of the body, wherever necessary.


d) Assimilation:

The blood transports absorbed food materials to different body cells where food materials become an integral component of the living protoplasm and are used for energy, growth, and repair. This is called the assimilation of food. In other words “The process of absorbed nutrients from digested food mixing into the protoplasm of body cells is called assimilation.” Transportation means of these nutrients from the digestive system to body cells are different in various organisms. In humans, this means is blood and lymph circulatory system.

Assimilation of food in human

e) Egestion:

In the last process of nutrition in animals, egestion is the act of excreting unusable or undigested material from a cell as in the case of single-celled organisms or from the digestive tract of multicellular animals. After the process of digestion and absorption, a large amount of material remains undigested. After absorption of nutrients from digested food rest waste parts, this food excreting from the body is called egestion. Different organisms have different organs for this process. In human anus and urinal tract are the main excretory organs.

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