Heterotrophic mode of nutrition is of three types.
They entirely or partially depend upon autotrophic plants for their food supply they grow on the stem of the host plant.
Example:
An organism obtains its food from dead and dying organic matter.
Example:
An organism has to obtain organic molecules from their environment because they cannot make their food from simple inorganic compounds. This type of nutrition is known as holozic nutrition.
Example:
Nutrition in unicellular organisms like Amoeba is known as holozoic nutrition. It involves ingestion by the cell surface, digestion and egestion. Amoeba takes in complex organic matter as food.
Ingestion by the cell surface:
Amoeba first identifies its food then throws out a number of small pseudopodia (projections of cytoplasm, also called false feet). These pseudopodia enclose the food particle and prevent it from escaping. The food enclosed in the cell membrane forms a food vacuole.
Digestion:
The complex food is broken down into simpler molecules with the help of digestive enzymes produced by an organelle called lysosome. The digested food is distributed in the cytoplasm.
Egestion:
The undigested food is egested through the cell membrane.
OR
In Paramecium, a unicellular organism with a specific shape, food is ingested through a special opening, the cytostome (cell mouth). Food is brought to this opening by the lashing movement of cilia that cover the entire surface of the cell.
