How Do Organisms Obtain their Nutrition
There are many methods of obtaining nutrition in holozoic organisms. They depend upon the complexity of the Ptyalin partially dig organisms and the mode of their feeding. In all cases, holozoic nutrition involves five steps – ingestion, digestion absorption, assimilation, and egestion.
In unicellular organisms like Amoeba food can be taken in by the entire surface. As soon as a food part oesophagus. They come in contact with the cell surface, it sends out pseudopodia all around it. As the tips of pseudopodia fuse, the food particle comes to lie in a vacuole called food vacuole. With the help of digestive enzymes brought b lysosomes, the food particle is digested. Its soluble products pass into the surrounding cytoplasm. The insoluble ingredients contained in the vacuole rise to the surface and are thrown out.
In some unicellular organisms like Paramecium, the cell has a definite shape, and food is taken in through a temporary mouth or cytosome by cilia. After digestion, the digestible particles are thrown out through another temporal opening called cytology.
In multicellular organisms, different parts of the body become specialized to perform different functions-ingestion by mouth, digestion in the alimentary canal, circulation of digested food, its absorption and assimilation by individual cells. The undigested part of food is thrown out of the alimentary canal in the process called egestion.