Nutrition is a science dealing with the composition of food, food intake and its assimilation in the body. It includes food, ingestion, digestion, absorption and egestion.
Types of Nutrition
Nutrition is the process of obtaining nourishment. It includes food, ingestion, digestion, absorption and egestion. Protozoans exhibit 6 types of Nutrition. They are as follows:
Holophytic nutrition. Holozoic nutrition, Saprozoic nutrition,mixotrophic nutrition, parasitic nutrition and coprozoic nutrition.
Here the protozoans synthesize carbohydrate by photosynthesis. They are provided with chlorophyll. They synthesize carbohydrate with the help of CO_2, water and animals. Holophytic nutrition is exhibited by protozoans bearing chlorophyll. Eg. Euglena, Chlamydomonas, Volvox, etc.
This type of Nutrition is like that of animals. In this type, the solid or semi-solid food is swallowed. Eg. Amoeba.
The absorption of decayed organic materials as food is called Saprozoic Nutrition. The food consists of decayed plants and decayed animals. They are absorbed in solution through the general body surface. Eg. Euglena, Entamoeba, etc.
Certain protozoans feed by more than one method. Eg. Euglena. It exhibits holophytic nutrition, holozoic nutrition and Saprozoic Nutrition.
Parasites obtain their food from their hosts. They feed by holozoic method Saprozoic method. Parasites may feed on the digested food of the host or on the tissues of the host. Trypanosoma feeds on blood by Saprozoic method. Trichomonas feeds on the digested food.
In this method, the faecal materials are swallowed as food. It is exhibited by Copromonas living in the faeces of vertebrates.