Class 10 Science

Life Processes: Nutrition in Animals

These notes are based on the chapter life processes from class 10 science NCERT book and CBSE syllabus.

  • Steps of holozoic nutrition
  • Nutrition in amoeba
  • Nutrition in Humans

In the previous section, you have read that when an organism takes food from another organism, it is called heterotrophic nutrition. Different heterotrophic organisms follow different methods to take and utilize food. Based on this, heterotrophic nutrition can be divided into two types, viz. saprophytic nutrition and holozoic nutrition.

In case of saprotrophic nutriton, digestion takes place outside the body, i.e. before food is ingested. In case of holozoic nutrition, digestion takes place after ingestion, i.e. inside the body. Amoeba shows a good example of holozoic nutrition and so do human beings.

In this section, you will read about various steps of holozoic nutrition. You will also read about nutrition in amoeba and human.

Steps of Holozoic Nutrition

  1. Ingestion: The process of taking in the food is called ingestion. Different animals use different strategies and methods for ingestion of food. For example; birds have beaks to catch food but birds cannot chew food. Humans have teeth for chewing their food. Crocodiles cannot chew food rather they just break their prey into somewhat smaller pieces. Snakes swallow their food as a whole.
  2. Digestion: The process of breaking complex food substances into simple molecules is called digestion. Simple molecules, thus obtained, can be absorbed by the body. Simple animals do not have specialised organs for digestion but complex animals have an elaborate digestive system for the purpose.
  3. Absorption: The process of absorption of digested food is called absorption. In complex animals, there is elaborate mechanism for absorption of digested food.
  4. Assimilation: The process of utilization of digested food; for energy and for growth and repair is called assimilation. For example; utilisation of food to make protein or to store fat is assimilation.
  5. Egestion: The process of removing undigested food from the body is called egestion.

Nutrition in Amoeba:

nutrition in amoeba

Fig: Nutrition in Amoeba

Amoeba is a unicellular animal which follows holozoic mode of nutrition. Amoeba's body is irregular in shape and the shape keeps on changing. The cell membrane of amoeba keeps on protruding to make pseudopodia. The term pseudopdia means false feet.

Amoeba surrounds a food particle with pseudopodia and makes a food vacuole. The food vacuole contains the food particle and water. Digestive enzymes are secreted in the food vacuole and digestion takes place. After that, digested food is absorbed from the food vacuole. Finally, the food vacuole moves near the cell membrane and undigested food is expelled out.

Nutrition in Humans

Human beings are complex animals, which have a complex digestive system. The human digestive system is composed of an alimentary canal and some accessory glands. The alimentary canal is divided into several parts, viz. oesophagus, stomach, small intestine, large intestine, rectum and anus. Salivary gland, liver and pancreas are the accessory glands which lie outside the alimentary canal.

Each organ of the digestive system has distinct role to play in digestion of food. Accessory glands secrete various enzymes and other substances which play important role in digestion of food. In the next part of this lesson, you will read about structure and function of human digestive system.

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