Protists are grouped according to whether they are animal-like, plant-like, or fungus-like.
Animal-like protists are called protozoans. They are unicellular and parasitic. Digestion in protozoans is intracellular. Circulation, respiration, and excretion are accomplished through diffusion. Most reproduce through binary fission (asexual) although some utilize conjugation (sexual).
Plant-like protists contain chlorophyll. They are both unicellular and multicellular (although multicellular forms have no organs or tissues).
Fungus-like protists are divided into three groups: mxyomycota ("plasmodial slime molds"), acrasiomycota ("cellular slime molds"), and oomycetes ("mildews and water molds"). Circulation, respiration, and excretion are all accomplished through diffusion. Reproduction can be asexual through fragmentation and the production of spores or sexual through conjugation and alternation of generations.
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