Final answer:
In unicellular organisms like amoebas, waste is excreted through exocytosis, where vesicles fuse with the cell membrane to expel waste into the environment.
Step-by-step explanation:
Some unicellular organisms, such as the amoeba, ingest food by a process called endocytosis. After a food vesicle fuses with a lysosome to digest the food, the waste has to be excreted from the cell. This excretion of waste is achieved by a process known as exocytosis. During exocytosis, vesicles containing waste material merge with the cell membrane, and then release their contents to the external environment. Exocytosis is the reverse of endocytosis, and it plays a crucial role in waste removal and in maintaining cellular homeostasis for unicellular eukaryotic organisms.