Excretion in Protozoans

Excretion of metabolic wastes is dope almost exclusively by diffusion. All protozoans are ammonotelic i.e., the end product of their nitrogen metabolism is ammonia, which is readily diffused in the surrounding medium.

Figure: a) Parumecium with cytopharynx, food and contractile vacuoles and nuclei b) Enlarged section of a contractile vacuole in Paramecium which collects water and expels it outside, performing osmoregulatory functions