Chapter 28 Protists Protists former name for diverse mostly multicellular organisms o Polyphyletic kingdom Divided up into many now o Originally classified based on how they looked basically anything that wasn t a plant animal or fungus Most Diverse Structurally and Functionally Most are single celled but can be multicellular or colonial Simplest eukaryotes but very complex at the cellular level Use base organelles plus others contractile vacuoles Nutritionally diverse o Photoautotrophs with chloroplasts o Heterotrophs that absorb and ingest stuff o Mixotrophs both photosynthesis and heterotrophic Reproduction varied All 3 types represented Endosymbiosis in Eukaryotic evolution o Endosymbiosis the process by which unicellular organism engulf other cells which become endosymbionts and ultimately host organelles Mitochondria first Photosynthetic cyanobacteria 2nd eventually evolved into plastids Gave rise to 2 lineages of algae photosynthetic protist Red and green algae DNA similar to that of cyanobacteria Plastids surrounded by 2 membranes with homologous proteins in the inner and outer membranes of cyanobacteria o Secondary endosymbiosis red and green algae taken in by heterotrophs and became symbionts Ex chlorarachniophytes from heterotroph engulfing green algae Nucleomorph vestigial nucleus found in cell and DNA still transcribed green algae DNA Plastids have 4 membranes inner outer membrane of cyanobacterium algal plasma membrane and then membrane of eukaryotic food vacuole Some protists have plastids with 3 membranes indicating that 1 was lose due to evolution 5 Supergroups of Eukaryotes Excavata Chromalveolates Rhizarians Archaeplastida Opisthokonts In the early 1990s it was thought that the amitochondriate protists no mitochondria and fewer membrane bound organelles were the oldest living eukaryotes o Now we know they have reduced mitochondria o Classification is an ongoing process 1 Excavata o Based on morphology of exoskeleton o Some have an excavated groove on one side o Each group is monophyletic the supergroup might not be o Diplomonads lack plastids Mitosomes Reduced mitochondria that don t have an electron transport chain Must respire anaerobically 2 nuclei Multiple flagella Many parasitic giardia causes diarrhea o Parabasalids lack plastids hydrogen as waste Parabasal fibers Trichomonas vaginalis STD Hydrogenosomes Reduced mitochondria that respire anaerobically and release o Euglenozoans have a rod with spiral or crystalline structure inside flagella Predatory heterotrophs photosynthetic and parasitic Kinetoplastid 1 large mitochondrion that has a mass of DNA Ex Tryposoma African sleeping sickness Fools immune cells by switching membrane surface proteins often Euglenid have a pocket at one end with 1 or 2 flagella Mixotrophs and heterotrophs Ex euglena 2 Chromalveolates o Large and diverse clade o Might have originated when a common ancestor engulfed photosynthetic alga Some have plastids with singular algal structure and genes Some have red algal genes in nuclear DNA Some lack or have reduced plastids like the red alga o Alveolates have alveoli membrane bounded sacs under their membrane unknown function might stabilize cell surface or regulate water and ion content Subgroup Dinoflagellates cells reinforced by cellulose plates 2 flagella in grooves of armor spin to move Mixotrophic and heterotrophic Phytoplankton Blooms can cause red tide because of toxins Subgroup Apicomplexans parasites of animals Spread by sporozoites End of sporozoite cell has a complex of organelles for penetrating host cells and tissues apex complex apicomplexan Plasmodium Vivax causes malaria o Hides in cells and changes cell surface markers often Subgroup Ciliates use cilia to move and feed Cilia might coat the entire organism or be clustered in one area 2 types of nuclei micronucleus and macronucleus o Macronucleic gene control everyday function of the cell Reproduces by binary fission Genetic variation obtained using conjugation o Macronucleus disintegrates and the micronucleus takes over Conjugation when 2 individuals exchange haploid nuclei but don t divide o Stramenopiles hairy flagellum paired with smooth flagellum Photosynthetic and heterotrophic Diatoms Glass like wall of hydrated silica that overlap like a petri dish Can withstand high pressure Very diverse Have a huge effect on CO2 levels Diatomaceous earth sediments of fossilized diatom walls Golden algae Yellow and brown because of carotenoids Biflagellated at 1 end of cell All photosynthetic some mixotrophic Most unicellular some colonial Can form protective long lasting cysts Brown algae Largest and most complex Brown olive color carotenoids Many sea weeds Some even have specialized tissues and organs that are analogous to plant tissues Thallus plantlike algal body o No true roots stems leaves o Holdfast anchors o Stem like stipe o Leaf like blades Adapted to rough water and low tides Oomycetes water molds white rusts and downy mildew Previously fungi but have differences o Wall of cellulose not chitin o Molecular systematics says they aren t fungi No plastids photosynthesis Decomposers and parasites Potato blight Alternation of generations alternation between multicellular haploid and diploid forms Sporophyte diploid individual that makes flagellated zoospores that make male female haploid gametophytes Gametophyte haploid individual that makes gametes that fertilize and make another sporophyte Heteromorphic sporophyte and gametophytes are structurally different 3 Rhizarians diverse group with DNA similarities amoebas o Radiolarians symmetrical tests of silica Radiating pseudopodia and reinforced by microtubules covered in a thin layer of cytoplasm for trapping and eating o Forams foramiferans have porous tests made of calcium carbonate Pseudopodia used for swimming test formation and feeding Sometimes have symbiotic algae in test Fresh and saltwater Can get large Widely fossilized o Cercozoans include amoeboid and flagellated protists with threadlike pseudopodia Marine freshwater and soil Most heterotrophs some parasites and predators 4 Archaeaplastida red algae green algae and land plants o Descended from a common ancestor that engulfed a cyanobacteria o Red algae rhodophytes Use reddish photosynthetic accessory pigment phycoerythrin Some might lack pigment and be parasites to other red algae Warm coastal waters of tropical oceans Many multicellular Alternation of generations rely on currents rather than flagella to
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