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Notes on Nutrition in animals
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Animal nutrition focuses on the dietary needs of animals, primarily those in agriculture and food production, but also in zoos, aquariums, and wildlife management. There are seven major classes of nutrients: carbohydrates, fats, fibre, minerals, proteins, vitamins, and water.
The nutritional requirements of most animals are relatively extensive and complex compared with the simple requirements of plants. The nutrients used by animals include carbohydrates, lipids, nucleic acids, proteins, minerals, and vitamins.
Nutrition in Amoeba
Amoeba is a microscopic organism which consists of only a single cell.
Amoeba is mostly found in pond water.
Figure given below shows the structure of amoeba.
structure of amoeba
Amoeba eats tiny plants and animals as food which floats in water in which it lives.
The mode of nutrition in Amoeba is holozoic.
The process of obtaining food by Amoeba is called phagocytosis.
Steps involved in the nutrition of Amoeba:
Ingestion: Amoeba ingests food by forming temporary finger-like projections called pseudopodia around it. The food is engulfed with a little surrounding water to form a food vacuole (‘temporary stomach’) inside the Amoeba.
Digestion: In Amoeba, food is digested in the food vacuole by digestive enzymes which break down the food into small and soluble molecules by chemical reactions.
Absorption: The digested simple and soluble substances pass out of food vacuole into the surrounding environment.
Assimilation: The absorbed food materials are used to obtain energy through respiration and make the parts of Amoeba cell which leads to the growth of Amoeba.
Egestion: The remaining undigested material is moved to the surface of the cell and thrown out of the body of Amoeba.
Nutrition in Paramecium:
Paramecium is also a tiny unicellular animal which lives in water.
Ingestion: Paramecium uses its hair like structures called cilia to sweep the food particles from water and put them into mouth.
Ingestion is followed by other steps such as digestion, absorption, assimilation and egestion which are same as those we studied in Amoeba.
Nutrition in Hydra
Hydra is a simple multicellular animal.
It has a number of tentacles around its mouth, which are used for ingestion of food.
These tentacles entangle small aquatic animals and kill them with their stinging cells.
After this they push them into their mouth. Now inside their body cavity digestive juices are secreted by the surrounding cells.
These juices digest the food and the digested food is absorbed through the cavity walls and assimilated in the cells.
Nutrition in Spider
In spiders digestion of food actually takes place outside their body.
A spider weaves a sticky web in which small insects get stuck.
It then injects digestive juices into the body of the insect, which digests the body part of the insects.
The spider then sucks up the digested food.