Nutrition in Animals

that can be absorbed by the body and provide nutrition. Nutrition is detined as the process of obtaining food and its utilisation by the body. In the previous chapter, we have learnt that green plants produce food by the process or photosynthesis. This mode of nutrition is known as autotrophic nutrition and green plants are Known as other organisns depend directly or indirectly on green plants for their Nutrition in Animals Unlike green plants, animals cannot make their own food. They depend either on plants or on Other animals for their food. This mode of nutrition is known as heterotrophic nutrition and these animals are known as heterotrophs. Types of Heterotrophic Nutrition There are four main types of holozoic Holozoicnutrition heterotrophic nutrition: parasitic saprotrophic symbiotic In holozoic nutrition, animals consume the solid or liquid food which is later broken down in the body. They are divided based on their food habits herbivores, carnivores, and omnivores. Herbivores eat only green plants. Cows, deer, camels are examples of herbivores. Carnivores feed onlyon the flesh of other animals. Lions, tigers, cheetahs are carnivores. Omnivores feed on both plants and other animals. Bears and pigs are omnivores. Humans are also omnivores, as we can consume foods from both plant and animal sources. Food obtained from plant sources include vegetables, fruits, cereals, pulses etc. Food obtained from animal sources include eggs, fish, meat and milk. Herbivore (Deer) Carnivore (Tiger) Omnivore (Bear) Fig. 2.1 Classification of animals based on their food habits Parasitic nutrition Animals that live inside or outside the body of other animals and obtain nutrition from them are called parasites. The animal in/ on which the parasite lives is harmed in this process because the parasite obtains nutrition directly from the body of the host. For example, a leech is a parasite that feeds on human and animal blood. A tapeworm is a parasite that lives in the intestines of other animals. .,.... It Saprotrophic nutrition decaying The bacteria Some mould) in other in Symbiotic nutrition is turn t h e nutrition Holozoic nutrition Parasitic differences a without organisms type digestion help living and from organic bacteria of to Fig nutrition harmingthem. in f i x heterotrophic 2. 2 between enter atmospheric the of matter. (a) are root food Both Tapeworm nutrition. 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Examples: Bacteria, fungi such as bread moulds. An association between two organsims in which both are benefitted. Examples: Bacteria found in the human intestine, the nitrogen-fixing bacteria rhizobium in the root nodules of leguminous plants. Fig. 2.3 Types of heterotrophic nutrition Steps in Holozoic Nutrition Holozoic nutrition involves 5 steps. Ingestion Ingestion The process of consuming food is known as ingestion. The food is first taken inside the body through the mouth. Some ways in which animals ingest food are: Humans andother animals ingest food through the mouth. Frogs and chameleons have long sticky tongues to catch Digestion their prey. Absorption Paramecium has hair-like cilia that pushes food into the cell. Assimilation Butterflies suck nectar from flowers with a long tube called proboscis. Digestion The food eaten by an animal is not utilised in the same form as it is ingested. It is broken down further into smaller and Egestion Fig. 2.4 Steps in holozoic nutrition simpler compounds so that it can be absorbed by the body. This process of breaking down food bythe enzymes into simple soluble forms to be absorbed by the body is known as digestion. Absorption The digested food contains nutrients and must be transported to all parts of the body. The process of extracting nutrients from the digested food and carrying them to all parts of the body is known as absorption. Assimilation the The nutrients absorbed from the food are utilised for growth, repair and maintenance of body. This process is known as assimilation. Egestion the undigested food along with After absorbing nutrients and useful substances from the food, is known as egestion. waste material is excreted from the body. This procesS