Nutrition: Energy is required for physiological function. Food is the source ofthis energy. Nutrition is a process, By this process Amoeba performs its food ingestion, digestion, absorption, assimilation and excretion of faecal materials Body reorganization and growth also occur through this process.
Food: Amoeba takes small algae, bacteria, diatom and various microorganisms as its food.
Process of intake of food: Amoeba has no digestive system. For the intake offood there is no mouth or any other fixed organ. At the time of food intake Amoeba becomes attached to a surface and with the help of pseudopodia ingest food by various methods. It can select organic and inorganic foods. It takes about 2 to 3 minutes to ingest the food. Amoeba intakes food mainly by the following five processes:
1. Circumvallation: In this process Amoeba takes mobile and solid foodsubstances. With the help of pseudopodia it surrounds the food material. Without touching the food material, the edges of the pseudopodia come close together and with the ectoplasmic membrane form the food vacuole along with water. When the pseudopodia surround the food material it looks like a cup. It is called "Food cup". The ectoplasm transforms into endoplasm and protects
2. Circumfluence: In this process Amoeba takes immobile food materials.Immediately after coming in contact with the food material, amoeba forms a "food cup" and by stretching the pseudopodia it brings the enclosed food in direct contact with the body. In this way, Amoeba takes the food material inside the body.
3. Import: If any food material comes on its body, by being motionless andwithout stretching any pseudopodia, Amoeba makes the food inactive. Then the inactive food material is taken inside the body. This is called import process.
4. Invagination: When the body of amoeba comes in contact with any foodparticle it secretes
sticky substance and fixes it with the body surface. Besides Amoeba secretes a kind of toxic juice from the body which kills the living food material. The ectoplasm along with the food enters the endoplasm in the form of a tube. Then the plasma membrane disappears and forms a food vacuole. In this process no pseudopodium is required to receive the food material.
5. Pinocytosis: In this process Amoeba takes liquid food materials. At manytimes in different parts of the body surface of Amoeba the plasmalema gets folded and enters into the endoplasm,"as a result of which a tube like structure is formed. This tube is called pinocytic tube. With liquid food materials the tube forms pinosome or small cavities, which later on is taken within the endoplasm.