Final answer:
An amoeba requires energy to expel waste through exocytosis using contractile vacuoles.
Step-by-step explanation:
An amoeba requires energy when it expels waste. Amoebas obtain energy by ingesting food through endocytosis. The food vesicle then fuses with a lysosome, which digests the food. Waste is excreted by exocytosis, where the contractile vacuoles merge with the cell membrane and expel waste into the environment.