bacteriology ch25

bacteriology ch25 - Chapter 25 Protists- a polyphyletic...

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Chapter 25 Protists - a polyphyletic collection of organisms; most are unicellular; lack the level of tissue organization present in higher eucaryote; can be photoautotrophic, chemoorganotrophic, or mixotrophic; usually reproduce asexually by binary fission; grow in a wide variety of moist habitats; most are free living; chemoorganotrophic forms play role in recycling nitrogen and phosphorus; terrestrial and planktonic forms; parasitic forms cause disease in humans and domesticated animals; photosynthetic protists are aerobic and most are photoautotrophic; chemoheterotrophic protists can be holozoic or saprozoic holozoic - solid nutrients such as bacteria are acquired by phagocytosis saprozoic – soluble nutrients cross plasma membrane by endocytosis, diffusion or carrier mediated transport osmotrophy – mechanisms by which soluble nutrients are assimilated mixotrophy – the use of both organic and inorganic forms of carbon plasmalemma - protist cell membrane; indentical to that of multicellular organism Encystation - some protozoa secrete resistant covering and go into dormant form called a cyst Excystment - release from cyst form; triggered by favorable environmental conditions Super-Group Excavata - includes Fornicata, the Parabasilia and the Euglenozoa; includes some of most primitive, or deeply branching eukaryotes; most have a cytostome;
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bacteriology ch25 - Chapter 25 Protists- a polyphyletic...

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