ch 28 - BIO EXAM II ch 28 I Protists eukaryotes that are...

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BIO EXAM II   ch 28 I) Protists: e ukaryotes that are neither plants, animals, nor fungi A) Most unicellular, most nutritionally diverse of euk. , habitats diverse, mostly aquatic B) evidence that much of protist diversity has its origins in endosymbiosis, a process in which certain unicellular organisms  engulfed other cells, which became endosymbionts and ultimately organelles in the host cell i) later in eukaryotic history, one lineage of heterotrophic eukaryotes acquired an additional endosymbiont—a  photosynthetic cyanobacterium—that then evolved into plastids ii) On several occasions during eukaryotic evolution, red algae and green algae underwent  secondary endosymbiosis : They  were ingested in the food vacuole of a heterotrophic eukaryote and became endosymbionts themselves. iii) Consistent with the hypothesis that chlorarachniophytes evolved from a eukaryote that engulfed another eukaryote, their  plastids are surrounded by  four  membranes. The two inner membranes originated as the inner and outer membranes of  the ancient cyanobacterium. The third mem brane is derived from the engulfed alga’s plasma membrane, and the  outermost membrane is derived from the heterotrophic eukaryote’s food vacuole . C) 3 categories: i) photosynthetic (plant-like) protists, or algae (singular,  alga );  ii) ingestive (animal-like) protists, or protozoans; and  iii) absorptive (fungus-like) protests D) protists nutritionally diverse i) some protists are photoautotrophs, containing chloroplasts. ii)  Some are heterotrophs, absorbing organic molecules or ingesting larger food particles. Still  iii) others, called  mixotrophs , combine photosynthesis  and  heterotrophic nutrition. II) A) Diplomonadida (the diplomonads) and Parabasala (the parabasalids). Protists in these two clades lack plastids, and their  mitochondria do not have DNA, electron transport chains, or enzymes that are normally needed for the citric acid cycle. i) Diplomonads      have two equal-sized nuclei and multiple flagella. ii)
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This note was uploaded on 04/18/2008 for the course BIOL 1308 taught by Professor Hauser during the Spring '08 term at St. Edwards.

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ch 28 - BIO EXAM II ch 28 I Protists eukaryotes that are...

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