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LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson Chapter 28 Protists Lectures by Erin Barley Kathleen Fitzpatrick © 2011 Pearson Education, Inc. Overview: Living Small • Even a low-power microscope can reveal a great variety of organisms in a drop of pond water • 300 years ago, the Dutch microscopist Antoni van Leeuwenhook stated: • “No more pleasant sight has met my eye than so many thousands of living things in a drop of water” © 2011 Pearson Education, Inc. Figure 28.1 1 m Concept 28.1: Most eukaryotes are single-celled organisms • Protists are eukaryotes • Eukaryotic cells have organelles and are more complex than prokaryotic cells • Most protists are unicellular, but there are some colonial and multicellular species © 2011 Pearson Education, Inc. Structural and Functional Diversity in Protists • Protists exhibit more structural and functional diversity than any other group of eukaryotes • Single-celled protists can be very complex, as all biological functions are carried out by organelles in each individual cell © 2011 Pearson Education, Inc. • Protists, the most nutritionally diverse of all eukaryotes, include – Photoautotrophs, which contain chloroplasts – Heterotrophs, which absorb organic molecules or ingest larger food particles – Mixotrophs, which combine photosynthesis and heterotrophic nutrition © 2011 Pearson Education, Inc. • Some protists reproduce asexually, while others reproduce sexually, or alternate between sexual and asexual cycles • Eukaryotes evolved by endosymbiosis © 2011 Pearson Education, Inc. The Evolutionary Origins of Mitochondria and Chloroplasts (Chapter 6) • Mitochondria and chloroplasts have similarities with bacteria – Enveloped by a double membrane – Contain free ribosomes and circular DNA molecules – Grow and reproduce somewhat independently in cells © 2011 Pearson Education, Inc. • The Endosymbiont theory – An early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host – The host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion – At least one of these cells may have taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplasts © 2011 Pearson Education, Inc. Figure 6.16 Endoplasmic reticulum Engulfing of oxygenusing nonphotosynthetic prokaryote, which becomes a mitochondrion Nucleus Nuclear envelope Ancestor of eukaryotic cells (host cell) Mitochondrion Nonphotosynthetic eukaryote At least one cell Engulfing of photosynthetic prokaryote Chloroplast Mitochondrion Photosynthetic eukaryote • Advances in eukaryotic systematics have caused the classification of protists to change significantly • Protists constitute a polyphyletic group, and Protista is no longer valid as a kingdom • Formerly 5 Kingdoms: • Monera, Protista, Plantae, Fungi, Animalia • Now: • 3 Domains: Bacteria, Archae, Eukarya © 2011 Pearson Education, Inc. Figure 26.21 Eukarya Land plants Green algae Dinoflagellates Forams Ciliates Diatoms Red algae Cellular slime molds Amoebas Euglena Trypanosomes Leishmania Animals Fungi Green nonsulfur bacteria Sulfolobus Thermophiles (Mitochondrion) Spirochetes Halophiles COMMON ANCESTOR OF ALL LIFE Chlamydia Green sulfur bacteria Bacteria Methanobacterium Archaea Cyanobacteria (Plastids, including chloroplasts) 5 Supergroups of Eukaryotes Parabasalids Euglenozoans Excavata Diplomonads Apicomplexans Ciliates Diatoms Stramenopiles Golden algae Chromalveolata Alveolates Dinoflagellates Brown algae Oomycetes Forams Radiolarians Green algae Chlorophytes Charophytes Land plants Archaeplastida Red algae Rhizaria Cercozoans Gymnamoebas Entamoebas Opisthokonts Nucleariids Fungi Choanoflagellates Animals Unikonta Amoebozoans Slime molds Figure 28.7 Euglena_Excavata Long flagellum Eyespot Short flagellum Light detector Contractile vacuole Nucleus Chloroplast Plasma membrane Euglena (LM) 5 m Pellicle Mixotroph = autotroph and heterotroph Trichonympha_Excavata Inhabits the guts of many termite species enabling them to digest wood (e.g. cellulose) Trypanosome_Excavata Parasites which causes sleeping disease in humans Paramecium_Chromalveolata Belongs to group of ciliates Sexual reproduction by conjugation, Asexual reproduction by binary fission Stentor_Chromalveolata Belongs to group of ciliates Vorticella_Chromalveolata Belongs to group of ciliates Balantidium coli_Chromalveolata Belongs to group of ciliates Parasites in humans (e.g. colon) to induce ulcers Amoeba_Unikonta (Sarcodina) Movement through pseudopodia (by reversible assembly of cytoskeleton) Radiolaria_Rhizaria (Sarcodina) Marine amoebas; cytoskeleton made of silica Foramnifera_Rhizaria (Sarcodina) Marine amoebas; porous shells consisting of organic material hardened with calcium carbonate Protists play key roles for ecology Protists have important roles as symbionts: • Photosynthetic dinoflagellates provide food for coral polyps that build coral reefs • Cellulose digesting protists in termites or ruminants © 2011 Pearson Education, Inc. Protists play key roles for ecology Other consumers Herbivorous plankton Carnivorous plankton Prokaryotic producers Protistan producers • Biomass of photosynthetic protists has declined as sea surface temperature has increased • If sea surface temperature continues to warm due to global warming, this could have large effects on – Marine ecosystems – Fishery yields – The global carbon cycle © 2011 Pearson Education, Inc.