CGPSC ACF – BIOLOGY- Nutrition in Animals

Nutrition in Animals

• It is the mode of taking food by an organism and its utilization by the body.

Types of Nutrition

1. Autotrophic nutrition

The term ‘autotroph’ is made up of two words ‘auto’and ‘troph’. Here ‘Auto’ means ‘self’ and ‘troph’ means ‘nutrition’.So , in autotrophic mode of nutrition is where the food is manufactured by the organism itself in the presence of sunlight by taking in raw materials such as carbon dioxide or water from the surrounding. All green plants, blue green algae & autotrophic bacteria have this mode of nutrition.

       The organisms which can make their own food in the presence of sunlight by taking carbon dioxide(CO₂) and water(H₂O) from their surroundings are called autotrophs. These organisms contains a green coloured pigment called chlorophyll which is capable of trapping solar energy. This solar energy is then used by plants for synthesizing food in the form of starch by combining carbon dioxide(CO₂) and water(H₂O) taken from the surrounding by the process called photosynthesis.

• Heterotrophs-The term ‘heterotroph’ consists of two words ‘hetero’and ‘troph’.

‘Hetero’ means ‘others’and ‘troph’means ‘nutrition’.So, in heterotrophic nutrition the organisms cannot make their own food from carbon dioxide, water and sunlight as they do not have chlorophyll. Such organisms depend on plants directly or indirectly for their food. All the animals, fungi, some protists and bacteria have heterotrophic mode of nutrition.

Types of Heterotrophic Nutrition

A heterotrophic organism can obtain its food from other organisms in following three ways:

1. Holozoic nutrition
2. Saprotrophic nutrition
3. Parasitic nutrition

1. Holozoic Nutrition

Holozoic nutrition takes place in those organisms which take solid or liquid food through the mouth inside their body Examples of organisms having holozoic mode of nutrition are human beings, dog, cat, lion, deer, crow, frog and fish etc. This process takes place in following steps:

1. Ingestion– The process of taking food inside the body is called ingestion.
2. Digestion-In digestion the ingested food is converted into simple form with the help of digestive enzymes.
3. Absorption-In this stage the food digested in second step is absorbed into the cells of body.
4. Assimilation-Assimilation is the process of utilizing the food absorbed in third step by various cells of the body.
5. Egestion– Egestion is the final step of holozoic nutrition in which the undigested food is removed from the body.

• Saprotrophic Nutrition or Saprophytes – Example Fungi

• In saprophytic nutrition the organisms obtain their food from dead and decaying organic matter of dead plants, dead animals and other decomposing organic matter. And the organisms which obtain their food from dead and decaying organic matter of dead plants, dead animals and other organic matter are called saprophytes. Fungi, bread mould, some protists and many bacteria are saprophytic in nutrition.
• Plants which use saprotrophic mode of nutrition are called saprotrophs. Mushrooms are best example.

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