Protozoa is a group of microscopic, and unicellular animalcules without tissue and organs, having one or more nuclei. Amoeba is free-living protozoan and-contains all the equipment required by the organism to perform all the vital functions of life. The contractile vacuole is for osmo-regulation. Cell wall is absent in animals. Amoeba is carnivorous and its mode of nutrition is holozoic i.e., it feeds by phagocytosis.