LECTURE 3: LIFE PROCESSES: NUTRITION IN ANIMALS

CLASS X   |    SCIENCE    |    LIFE PROCESSES

      Notes prepared by Subhankar Karmakar

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SCIENCE: CLASS X: CBSE (CLASS NOTES)

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• CLASSIFICATION OF ANIMALS ON THE BASIS OF FOOD HABITS

All the animals can be divided into three groups on the basis of their food habits or eating habits. These are:

• 1. Herbivores
• 2. Carnivores
• 3. Omnivores

• HERBIVORES
• Animals which eat only plants are called herbivores. 
• They are also called Herbivorous animals. 
• Some of the examples are goat cow buffalo horse etc. 

• CARNIVORES
• Those animals which eat only other animals as food are called Carnivores. 
• They eat only the flesh or meat of other animals.
• They are meat eaters.
• They are also called Carnivorous animals. 

• OMNIVORES
• Those animals which eat both, plants and animals, are called omnivores.
• They are also called omnivorous animals.
• Omnivores are plant eaters as well as meet eaters. 
• Human beings,  dog, are omnivorous animals.

Ultimately it is the energy of the Sun which provides food for plants and animals (herbivores, carnivores and omnivores).

• DIFFERENT STEPS IN THE PROCESS OF NUTRITION IN ANIMALS

There are five main processes concerned with the use of food by animals. They are as follows. 

• 1. Ingestion
• 2. Digestion
• 3. Absorption
• 4. Assimilation
• 5. Egestion
• INGESTION

The process of taking food into the body is called ingestion. When we put food into our mouth with hands we are ingesting. 

• DIGESTION

The process in which the food containing large, insoluble molecules is broken down into small, water soluble molecules, which can be absorbed by the body is called digestion. Most animals use both physical like chewing, grinding in mouth and chemical methods like breaking the large molecules using digestive juices like enzymes for digesting. 

• ABSORPTION

The process in which the digested food passes through the intestinal wall into blood stream is called absorption. 

• ASSIMILATION

The process in which the absorbed food is taken in by body cells and used for energy, growth and repair, is called assimilation. 

• EGESTION

A part of the food animals consume remain undigested as they are insoluble in water. The process in which the undigested food is removed from the body is called egestion. 

• NUTRITION IN UNICELLULAR ORGANISMS
• Amoeba is a unicellular organism. It eats microscopic animals and plants as food. The mode of nutrition in Amoeba is holozoic. 
• The process of obtaining food by Amoeba is called Phagocytosis. 
• It also follows the five steps processes for nutrition. 

• INGESTION IN AMOEBA

As Amoeba has no mouth or a fixed place for intake of food, Amoeba injests food by using its Pseudopodia, which is a temporary finger-like projections on the surface of the body. 

When a food particle comes near Amoeba, the food is engulfed with a little surrounding water to form a food vacuole inside the Amoeba. This food vacuole can be considered to be a "temporary stomach" of Amoeba. 

• DIGESTION IN AMOEBA

In Amoeba, food is digested in the food vacuole by digestive enzymes. The enzymes from surrounding cytoplasm enter into the food vacuole and breakdown the food into small and soluble molecules by chemical reactions. Therefore digestion in Amoeba takes place inside the food vacuole due to which the food become soluble.

• ABSORPTION IN AMOEBA

The digested food present in the food vacuole of amoeba is absorb directly into the cytoplasm of amoeba cell by diffusion. Since Amoeba consists of only one small cell it does not required blood system to carry the digested food. The digested food just spreads out from the food vacuole into the whole Amoeba cell. After absorption of food the food vacuole disappears.

• ASSIMILATION IN AMOEBA

A part of the food absorbed in Amoeba cell is used to obtain energy through respiration. The remaining part of absorbed food is used to make the parts of amoeba cell which lead to the growth of amoeba. Thus on assimilating food Amoeba grows in size and then Amoeba can reproduce by dividing into two daughter cells. 

• EGESTION IN AMOEBA

Amoeba has no fixed place for removing the undigested part of food. When a considerable amount of undigested food collected inside amoeba, then it cell membrane suddenly ruptures at any place and the undigested food is thrown out of the body of amoeba. 

• PARAMECIUM

Paramecium is also a tiny unicellular animal which lives in water. Paramecium uses its hair like structures called Cilia to sweep the food particles from water and put them into its mouth. 

Unlike amoeba paramecium has a mouth and it has cilia all over its body. When the cilia present around the mouth region of paramecium move back and forth, they sweep the food particles present in water into the mouse a paramecium. This is egestion for paramecium.