In which of the following organisms is ammonia excreted as a waste product?

Ammonia is a highly toxic substance that needs to be eliminated from the body as soon as possible. In some organisms, ammonia is excreted directly as a waste product, while in others, it is converted into less toxic substances before excretion. Among the given options, Amoeba is an organism that excretes ammonia as a waste product. Amoeba is a unicellular organism that lives in water and has a simple structure. It does not have specialized excretory organs like kidneys, so it excretes metabolic waste directly through its cell membrane by diffusion. Since ammonia is highly soluble in water, it can diffuse out of the cell easily, making ammonia the primary excretory product of Amoeba. In contrast, humans, birds, and Spirogyra excrete urea or uric acid, which are less toxic and more water-conserving than ammonia.