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Lecture 2-11&12 - Lecture 12 Eukaryotic Diversity...

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Lecture 12 Eukaryotic Diversity 3/11/2011 © Nicola Davies 2011 Diversity: Eukaryotes Lectures 12 & 13 March 11 & 21, 2011 2 Eukaryotic Microbes Larger than prokaryotic microbes Vary greatly in size and shape Exploit a wide variety of niches: water, soil, in and on plants and animals Diverged from prokaryotes, acquiring greater structural complexity Mitochondria and chloroplasts are prokaryotic remnants Appeared about 2 billion years ago Multicellular life arose less than 1 billion years ago Divided into two groups: fungi and protists Protists: protozoa + microscopic algae Protozoa are non-photosynthetic, motile, unicellular Algae are photosynthetic Not taxonomic divisions 3 Eukaryotic Exceptions Exceptions to the eukaryotic body plan: Giardia has no mitochondria Likely had and then lost mitochondrial precursor Hydrogenosomes in some protozoa Convert pyruvate to acetate, CO 2 and H 2 Contain no DNA (except in Nycotherus ovalis ) Have surrendered genes to the eukaryotic chromosome 4 Eukaryotic Diversity: Fungi Very important ecologically and economically Decomposers recycle nutrients through ecosystems Most vascular plants require symbiotic fungi (mycorrhizae) inhabiting their roots to supply essential nutrients Provide drugs including penicillin Eaten as mushrooms, truffles and morels Necessary for bread, champagne, beer Causative agent of numerous diseases in plants and animals Ringworm, athlete’s foot, more serious and systemic diseases Very difficult to treat because humans and fungi are both eukaryotic Plant diseases include rusts, smuts and rots Can devastate crops Important as model organisms for studying eukaryotic biology 5 Fungi The Commonalities Non-photosynthetic, organic carbon source Do not ingest nutrients by phagocytosis Unique cell walls of chitin and other polymers Can grow vegetatively by extending filaments Can grow without free water in humid conditions Frequently interact with other organisms in symbioses and as pathogens Most are filamentous Filament = a hypha (a group of hyphae = mycelium) Act as decomposers, breaking down complex organic compounds (indigestible by most organisms) Form symbioses with wood-eating insects 6 The Yeasts: Saccharomyces cerevisiae Phylum: Ascomycota Bakers/brewers yeast Replicates by budding Intensely studied as a model eukaryotic organism Regulation of gene expression Control of cell cycle and cell division Can grow with a single carbon source and mineral salts Doubles every 2 hours in rich media and produces visible colonies within 2 days Grows aerobically or anaerobically Aerobically: respires - oxidizes carbon source to CO 2 & H 2 O Anaerobically: ferments sugars to CO 2 and ethanol
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Lecture 12 Eukaryotic Diversity 3/11/2011 © Nicola Davies 2011 7 Division of Budding Yeast Division is asymmetrical
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