Protozoa are unicellular eukaryotes that have relatively complex internal structures for complex metabolic activities.
Amoeba, Paramoecium, Plasmodium are examples of protozoa.
Contractile vacuole :
Excretory organ of protozoa is the Contractile vacuole which isa multipart organelle that collects water from the cytoplasm and removes it from the cell.
Contractile vacuoles excrete waste by diffusion method.