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Introduction to Protists Origin of Eukaryotes • First eukaryotic organism thought to have evolved about 1.5 billion years ago • Protozoans possible evolved from the 1st eukaryotes by Endosymbiosis • Endosymbiosis – process where one prokaryote lives inside another becoming dependent upon each other Origin of Eukaryotes Eukaryotic cell more complex than prokaryotic cell: • Membrane-bound nucleus and organelles • Chromosomes consist of DNA and histone proteins and occur in pairs. • Protists, fungi, plants & animals are composed of eukaryotic cells. Prokaryotic Cells Eukaryotic Animal Cell Typical Animal Cell Eukaryotic Plant Cell Typical Plant Cell Animal Vacuole Functions • Storage • Support • Water Regulation vacuole Plant mitochondria chloroplasts Both cell types have membrane-bounded organelles Origin of Eukaryotes Endomembrane infolding Infolding of membrane system forming nucleus and ER Origin of Eukaryotes Evolution of eukaryotic cellEndosymbiosis • Theory proposed by Mereschkovsky and refines by Margulis- serial endosymbiosis • Mitochondria and plastids were prokaryotes that invaded larger cells • Endosymbiont, ancestral mitochondria: Aerobic, heterotrophic & prokaryotic Origin of Eukaryotes • Ancestral chloroplasts were photosynthetic, prokaryotes that became endosymbionts • Relationship began as parasitic or undigested prey • Assumed here that endomembrane infolding evolved first, i.e., cell already evolved nucleus, ER, … Endosymbiosis Hypothesis A A prokaryote ingested some aerobic bacteria. The aerobes were protected and produced energy for the prokaryote A Aerobic bacteria C B Mitochondria D Cyanobacteria Chloroplasts N N N Plant cell Prokaryote N Animal Cell Endosymbiosis Hypothesis Over a long period of time the aerobes became mitochondria, no longer able to live on their own B A Aerobic bacteria C B Mitochondria D Cyanobacteria Chloroplasts N N N Plant cell Prokaryote N Animal Cell Endosymbiosis Hypothesis C Some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments A Aerobic bacteria C B Mitochondria D Cyanobacteria Chloroplasts N N N Plant cell Prokaryote N Animal Cell Endosymbiosis Hypothesis Cyanobacteria became chloroplasts, unable to live on their own D A Aerobic bacteria C B Mitochondria D Cyanobacteria Chloroplasts N N N Plant cell Prokaryote N Animal Cell Secondary Endosymbiosis and Origin of Algal Diversity Algae AB N N Secondary endosymbiosis N Heterotroph C Algae ABC Many membrane layers Fig. 28-02-2 Secondary Endosymbiosis Plastid Dinoflagellates Secondary endosymbiosis Cyanobacterium Apicomplexans Red alga Primary endosymbiosis Stramenopiles Heterotrophic eukaryote Over the course of evolution, this membrane was lost. Secondary endosymbiosis Plastid Euglenids Secondary endosymbiosis Green alga Chlorarachniophytes LUCA model places the archaea as more closely related to eukaryotes than they are to prokaryotes. Common ancestral community of primitive cells model • All three domains seem to have genomes that are chimeric mixes of DNA that was transferred across the boundaries of the domains. Fig. 28.8 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Five Supergroups Excavata Chromalveolata Rhizaria Archaeplastida Unikonta Euglenoids Dinoflagellates, diatoms, golden and brown algae Forams and radiolarians Red and green algae Slime molds Kingdom Protista Plantae Fungi Animalia eukaryotic Protista prokaryotic Monera Kingdom Protista • Eukaryotic • Mostly unicellular • A very heterogeneous group include both heterotrophic and photoautotrophic forms • 11 phyla • Lots of disagreements • Whittaker = “leftovers” Reproduction: • binary fission splits into two asexually • multiple fission producing more than two individuals • sexually by conjugation (opposite mating strains join & exchange genetic material) Kingdom Protista 3 informal groups Animal-like protists Fungus-like protists Plant-like (algal) protists Misleading: some change ~ 45,000 species Kingdom Plantae Kingdom Animalia Kingdom Fungi Chlorophyta Phaeophyta Rhodophyta Chrysophyta Euglenophyta Myxomycota Ciliophora Mastigophora Sarcomastigophora Apicomplexa Pyrrophyta Kingdom Protista Animal-like Protists Amoeba Cilliates Flagellates 13,000 species Animal-like Protists • Classified by the way they move cilia flagella pseudopodia • Heterotrophs ingest small food particles & digest it inside food vacuoles containing digestive enzymes Animal-like protists • Sarcomastigophora (amoebas, forams, radiolarian) • Ciliophora (paramecium) • Zoomastigophora (trypansoma) • Apicocomplexa (Sporozoa) Animal-like Protists Phylum Sarcomastigophora “Amoeba” Shell-like glass or calcium carbonate structures Radiating projections 13,000 species Note: glass projections Foraminifera Tropics = beaches Most have symbiotic algae Foramenifera: Globigerina ooze Covers about 36% of the ocean floor Animal-like Protists Phylum Ciliophora (“ciliates”) Largest, most homogeneous Share few characteristics with others Movement coordinated Sex: 8 mating types 8,000 species Paramecium Diatoms Plant-like Protists • • • • • • • Dinoflagellates Diatoms Euglena Cocolithophore Green algae Brown Algae Red algae Dinoflagellates Cocolithophore Radiolarian Plant-like Protists Phylum Pyrrophyta (“dinoflagellates”) Marine and Freshwater Some live in corals Cause “red tide” 1,100 species Zooxanthellae in Coral Polyp Bioluminescence Pyrocystis fusiformis Plant-like Protists Phylum Chrysophyta (“diatoms & golden algae”) Link to green algae 13,000 species Plant-like Protists Phylum Euglenophyta (“euglenoids”) 800 species Division Chlorophyta “Green algae” Most freshwater or terrestrial Some marine 7,000 species Chlorophyta: Green Algae Halimeda opuntia Codium edule Caulerpa sertularioides Caulerpa racemosa Dictyosphaeria cavernosa Division Phaeophyta “Brown algae” Marine habitats Example: giant kelp forests 1,500 species Example of complex morphology: Macrocystis a. holdfast - attaches to substrate Blade b. stipe c. blade - main organ of photosynthesis d. bladder - keeps blades near the surface Bladder Stipe Holdfast Laminaria Life Cycle Phaeophyta: Brown Algae Padina japonica Hydroclathrus clathratus Turbinaria ornata Sargassum polyphyllum Sargassum echinocarpum Division Rhodophyta “Red algae” Most in marine habitats 4,000 species Rhodophyta: Red Algae Acanthophora spicifera Galaxaura fastigiata Ahnfeltia concinna Hypnea chordacea Asparagopsi s taxiformis Acanthophora Gracilaria Hypnea Avrainvillae Halimeda opuntia Kappaphycus Eucheuma Super Sucker Inquiry 1. Identify 2 organisms that have a mutualistic symbiotic relationship with an other organism. 2. Read pages 510 – 514 Chpt 20 3. Alternation of Generations ( two examples)