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They evolved from a green alga by secondary

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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 Pellicle= thin layer of elastic proteins just under the PM protects the cell and allows it to retain a particular shape Anaerobic Flagellates o Diplomonads and parabasalids have multiple flagella & among the few protists adapted to oxygen poor waters Have HYDROGENOSOMES= organelles that produce ATP by an aerobic pathway and release H2 gas as a by product. 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
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