chap 25 notes

chap 25 notes - Protists Eukaryotes most are unicellular...

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Protists Eukaryotes, most are unicellular, some form colonies, some are coenocytic=lots of cytoplasms Nucleus surrounded by nuclear envelope, contain plastids and mitochondria, 9+2 flagella Some are multicellular, relatively simple body forms. Movement by pseudopodia, flexing over cells, gliding, waving cilia, flashing flagella Nutrients: autotrophic/heterotrophic (photosynthesis, absorption, ingestion) Mutualism, Commensalism: one benefits, Parasitism: one depends on the other. Most protists are aquatic, make up most of plankton Protists don’t develop multicellular reproductive organs. Evolution Protists (i.e. zooflagellates): first eukaryotic cells to evolve from ancestral prokaryotes. Serial Endosymbiosis Eukaryotic organelles arose from symbiotic rel’s between larger cells/smaller prokaryotes Mitochondria arose from aerobic bacteria (rRNA from mitochondria matches purple bacteria) Cyanobacterium + host cell (primary endosymbiosis) = chloroplasts Chloroplasts provided nonphotosynthetic eukaryotes chloroplasts during secondary endosym. 3 mems envelop chloros of euglenoids & dinoflagellates, 4 with diatoms & green/brown algae Apicomplexans (protists that cause malaria) (Plasmodium) have nonfunctional chloroplasts Chloroplasts surrounded by 4 membranes Drugs that inhibit chloroplasts also kill plasmodium Eukaryote Classification Molecular & ultrastructure research phylogenetic relationships amongst protists Molecular data obtained for the gene that code for SSU rRNA in different eukaryotes Ultrastructure = fine details of cell structure revealed by electron microscopy Similar structural patterns suggest certain taxa are monophyletic Water molds, diatoms, golden algae, brown algae = all monophyletic Protist Kingdom = Paraphyletic (some descendants of a common eukaryotic ancestor) Representative Protists Eight Major Clades: excavates, discicristates, alveolates, heterokonts, plants, cercozoa,
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chap 25 notes - Protists Eukaryotes most are unicellular...

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