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Nutrition in Animals

Nutrition in Animals

We know that plants prepare their own food, but animals eat plants and other animals for food.

What are the components of the food consumed by animals?

Carbohydrates, fats, proteins, minerals, and vitamins are the components of the food consumed by animals. However, some components of food are complex and cannot be utilized by the body of an animal in that form. Then, how do animals utilize these components?

Complex components of food like carbohydrates are broken down into simpler substances and are then utilized by the body. This process of breaking down of complex substances into simpler substances is known as digestion.



Consumers: These organisms mainly obtain food either directly from autotrophs or indirectly from other heterotrophs. They include animals that generally ingest and then digest their food.

Consumers are divided into herbivores, carnivores, and omnivores.




The animals that feed only on plants are called herbivores. They are also known as primary consumers.

The animals that eat other animals are called carnivores. They are also known as secondary consumers.

Those carnivores, which feed on herbivores, are called primary carnivores.

There are some animals that feed on both plants and animals.
Examples include deer, rabbit, goat, horse, sheep etc. Examples include lion, cat, tiger, leopard etc. Examples include bear, turtle, squirrel, humans etc.

Decomposers: This group includes micro-organisms such as bacteria and fungi, which obtain nutrients by breaking down the remains of dead plants and animals.

Do you know consumers can be further classified as

Sanguivores: These organisms feed themselves by sucking the blood of other organisms. Example- mosquitoes, bats etc.
Frugivores: These organisms feed totally or primarily on fruits. Example- parrots etc.
Granivores: These organisms feed mainly or only on grains. Example- pigeons etc.
Insectivores: These organisms feed on insects. Example- frogs, lizards etc.
Carrion eaters or Scavengers: These organims feed on decaying flesh of dead animals. Example- vultures, hyenas etc.

Different animals have different modes of feeding.

  • Cats eat small animals such as rats, birds, insects etc.

  • Cows eat grass, while birds feed on insects.

  • Some animals such as snakes swallow their prey entirely.

  • Bees and humming birds feed by sucking nectar from flowers.

Some Interesting Facts:

  • Did you know that a starfish pops out its stomach through its mouth to catch its prey? The stomach then goes back inside the body and the food is slowly digested.

  • Did you know that only female mosquitoes bite humans to suck blood? Male mosquitoes feed on nectar from flowers.

Each organ is placed at a different position in the alimentary canal. Hence, each organ performs a different function.

Let us recall the functions of digestive organs and relate them to the process of digestion.


The process of digestion occurs in five distinct steps. These are as follows.


1.Ingestion: The process of taking in food through the buccal cavity is known as ingestion.

2.Digestion: It is the process of breaking down food into simpler substances.

3.Absorption: The process of absorption takes place in the small intestine. Here, the digested food is absorbed in the blood through the villi, which are finger-like projections.


4.Assimilation: The food absorbed by blood is transported to various parts of the body by blood vessels. This process is known as assimilation.

5.Egestion: The process of removing the undigested food material from the body through the anus is known as egestion.

Process of Digestion of Food

The process of digestion includes both mechanical and chemical digestion. The mechanical process starts in the mouth when the teeth cut and grind the food into smaller pieces. The chemical digestion too starts in the mouth when the saliva mixes with the food.

Digestion of carbohydrates occurs mainly in the mouth and small intestine. Digestion of fats occurs mainly in the small intestine while proteins are basically digested in stomach and small intestine.

Absorption of the digested nutrients is mainly carried out by large intestine.

Absorption of Food

In the small intestine, the digestion of proteins, fats, and carbohydrates is completed.

Thereafter, the digested nutrients are absorbed by the finger-like projections present in the small intestine called villi. Villi have a higher surface area for absorption and they constantly move back and forth in a wave-like motion. Villi contain numerous small blood capillaries where the nutrients are absorbed in the blood.

Assimilation and Egestion

Mucus secreted by large intestine adhere the undigested particles into faeces. The excess of water from the food is absorbed by the large intestine.

Faeces enter rectum and are stored here. The faeces are eliminated through the anus at regular intervals. This …

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