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Transcript
Chapter 28 The Origins of Eukaryotic Diversity General characteristics Classification criteria – eukaryotes – not animal, plant or fungi Protist Diversity The full spectrum of modes of life – – – – – from unicellular to multicellular autotrophic to heterotrophic asexual to sexual reproduction pathogenic to beneficial sessile to mobile Mobility How Protists move – flagellum – cilia – pseudopod Protists Ingestive (animal-like); ameoba, paramecium, stentor Absorptive (fungus-like) Photosynthetic (plant-like); alga, kelp The Endosymbionic Theory Mitochondria and chloroplasts were formerly from small prokaryotes living within larger cells (Margulis) Endosymbiosis Evolution of eukaryotes – origin of mitochondria – engulfed aerobic bacteria, but did not digest them – mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Ancestral eukaryotic cell Eukaryotic cell with mitochondrion Endosymbiosis Eukaryotic cell with mitochondrion Evolution of eukaryotes – origin of chloroplasts – engulfed photosynthetic bacteria, but did not digest them – mutually beneficial relationship • natural selection! photosynthetic bacterium chloroplast Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion mitochondrion Theory of Endosymbiosis Evidence – structural • mitochondria & chloroplasts resemble bacterial structure – genetic Lynn Margulis • mitochondria & chloroplasts have their own circular DNA, like bacteria – functional • mitochondria & chloroplasts move freely within the cell • mitochondria & chloroplasts reproduce independently from the cell Protist Systematics & Phylogeny, I 1- Groups lacking mitochondria; early eukaryotic link; Giardia (human intestinal parasite; severe diarrhea); Trichomonas (human vaginal infection) 2- Euglenoids; autotrophic & heterotrophic flagellates; Trypanosoma (African sleeping sickness; tsetse fly) Protist Systematics & Phylogeny, II Alveolata: membrane-bound cavities (alveoli) under cell surfaces; dinoflagellates (phytoplankton); Plasmodium (malaria); ciliates (Paramecium) Protist Systematics & Phylogeny, III Stamenophila: water molds/mildews and heterokont (2 types of flagella) algae; numerous hair-like projections on the flagella; most molds are decomposers and mildews are parasites; algae include diatoms, golden, and brown forms Protist Systematics & Phylogeny, IV Rhodophyta: red algae; no flagellated stages; phycobilin (red) pigment Chlorophyta: green algae; chloroplasts; gave rise to land plants; volvox, ulva Protist Systematics & Phylogeny, V Affinity uncertain: Rhizopods: unicellular with pseudopodia; amoebas Actinopods: ‘ray foot’ (slender pseudopodia; heliozoans, radiolarians Protist Systematics & Phylogeny, VI Mycetozoa: slime molds (not true fungi); use pseudopodia for locomotion and feeding; plasmodial and cellular slime molds Protist Diversity Beneficial & necessary Protists – phytoplankton • small algae + diatoms • much of the world’s photosynthesis • produces ~90% of atmospheric oxygen – zooplankton • heterotrophic protists + animals • key ecological role at base of marine food web