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These protists ingest food, or have an animal-like mode of nutrition, and are heterotrophic. They ingest bacteria, other protists and detritus (dead organic matter). There are also symbiotic protozoa which are parasites that cause disease. Different types of protozoa include:
Rhizopods: unicellular amoebas with pseudopodia for mobility and feeding that reproduce by mechanisms of cell division asexually. Most are free-living, but some are parastitic (eg entamoeba histolytica which causes dysentery in humans.)
Actinopoda: Usually spherically symmetrical, feed with axopedia and have radiating pseudopodia supported by internal microtubules. They are components of plankton and there are two different varieties: heliozoans (which live in fresh water) and radiozoans (which are marine.)
Foraminifera (forams): marine protists that have multi-chambered shells hardened by calcium carbonate. Strands of cytoplasm extend through the pores, allowing them to swim and feed.
Apicomplexa: parasitic protists with complex life cycles in animal hosts, disseminating as tiny infectious cells called sporocytes and often requiring asexual and sexual stages during their life cycle.
Zoomastigophora (Zooflagellates): this heterotrophic protist uses flagella for propulsion and absorbs molecules or consumes them by phagocytosis. They are mostly solitary, but some live in colonies, and can be free-living, symbiotic or parasitic.
Ciliophora (ciliates): these protists use cilia for mobility and feeding. They mostly are solitary and live in fresh water. They have several unique characteristics, such as cytoplasmic organization and not genes directly providing hereditary information, and the presence of two types of nuclei, a large macronucleus and several tiny micronuclei. They generally reproduce by binary fission.