Evolve from mitochondria and adapt organisms to

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Evolve from mitochondria and adapt organisms to anaerobic aquatic habitats Thrive deep in seas and lakes & others live in animals Diplomonad Giardia lamblia o Can infect human gut= giardiasis Attaches to intestinal lining and takes up nutrients Excreted in feces if infected Protistan cyst is a dormant cell with a thick protective wall Parabasalid Trichomonas vaginalis o Infects human reproductive tracts and causes trichomoniasis o Doesn’t make cysts o Anti-protozoal drug provides cure Trypanosomes and other Kinetoplastids o Kinetoplastids Flagellated protozoans that have a single large mitochondrion Inside mito., near base of flagellum have clump of DNA Some prey of bacteria in fresh water and seas, but…
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o Trypanosomes= the largest subgroup, are parasitic Live in plants and animals Long, tapered cells with an undulating membrane Wavelike motion—single flagellum Biting insects act as vectors for many of these that parasitize humans Euglenoids= flagellated protists closely related to kinetoplastids o Most live in fresh water and none are human pathogens o Tiny predators, few are parasites of larger organisms, and about a third have chloroplasts o Structure of euglenoid chloroplasts and the pigments inside them indicate that they evolved from a green alga by secondary endosymbiosis o Photosynthetic euglenoids: detect light with an eyespot near base of long flagellum revert to heterotrophic nutrition if light levels decline or conditions for photosynthesis become otherwise unfavorable o hypertonic relative to fresh water o Contractile vacuoles= counter the tendency of water to diffuse into the cell Excess water collects in contractile vacuoles, which contract and expel it to the outside 21.4 Foraminifera and Radiolarians Related lineages of primarily heterotrophic single celled protists that secrete a sieve-like shell o Feed by capturing bits of organic debris and tiny organisms on threadlike or branching cytoplasmic extensions that stick out through the shell’s openings o Few are members of marine plankton o Plankton= collection of mostly microscopic organisms that drift or swim in open waters Chalky- Shelled Foraminifera
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o Foraminifera= secrete a Calcium Carbonate (CaCO3) shell o As large as a grain of sand o Most live on seafloor where they probe the water and sediments for prey o Over time geologic processes transform the accumulation CaCO3 rich shells of foraminifera and other marine organisms into deposits of limestone and chalk Glassy-Shelled Radiolarians o Radiolarians= secrete a glassy silica shell with two cytoplasmic layers
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