Chapter 28 Protists

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 Figure 28.1 Which of these organisms are prokaryotes and which are eukaryotes? 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.

Eukaryotes evolved by endosymbiosis 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.

Endoplasmic reticulum Nucleus Figure 6.16 Endoplasmic reticulum Nucleus Engulfing of oxygen- using nonphotosynthetic prokaryote, which becomes a mitochondrion Nuclear envelope Ancestor of eukaryotic cells (host cell) Mitochondrion Engulfing of photosynthetic prokaryote At least one cell Figure 6.16 The endosymbiont theory of the origin of mitochondria and chloroplasts in eukaryotic cells. Chloroplast Nonphotosynthetic eukaryote Mitochondrion Photosynthetic eukaryote

Monera, Protista, Plantae, Fungi, Animalia Now: 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.

Eukarya Bacteria Archaea Figure 26.21 Land plants Dinoflagellates Green algae Forams Ciliates Diatoms Red algae Amoebas Cellular slime molds Euglena Trypanosomes Animals Leishmania Fungi Sulfolobus Green nonsulfur bacteria Thermophiles (Mitochondrion) Figure 26.21 The three domains of life. Spirochetes Halophiles Chlamydia COMMON ANCESTOR OF ALL LIFE Green sulfur bacteria Bacteria Methanobacterium Cyanobacteria Archaea (Plastids, including chloroplasts)

5 Supergroups of Eukaryotes Diplomonads Parabasalids Euglenozoans Excavata Dinoflagellates Apicomplexans Ciliates Diatoms Golden algae Brown algae Oomycetes Alveolates Chromalveolata Stramenopiles Cercozoans Forams Radiolarians Rhizaria Red algae Chlorophytes Charophytes Land plants Green algae Figure 28.3 Exploring: Protistan Diversity. Archaeplastida Slime molds Gymnamoebas Entamoebas Nucleariids Fungi Choanoflagellates Animals Amoebozoans Unikonta Opisthokonts

Mixotroph = autotroph and heterotroph Figure 28.7 Euglena_Excavata Long flagellum Eyespot Short flagellum Light detector Contractile vacuole Nucleus Figure 28.7 Euglena, a euglenid commonly found in pond water. Chloroplast Plasma membrane Pellicle Euglena (LM) 5 m Mixotroph = autotroph and heterotroph

Trichonympha_Excavata Figure 28.7 Euglena, a euglenid commonly found in pond water. Inhabits the guts of many termite species enabling them to digest wood (e.g. cellulose)

Trypanosome_Excavata Figure 28.7 Euglena, a euglenid commonly found in pond water. Parasites which causes sleeping disease in humans

Paramecium_Chromalveolata Figure 28.7 Euglena, a euglenid commonly found in pond water. Belongs to group of ciliates Sexual reproduction by conjugation, Asexual reproduction by binary fission

Stentor_Chromalveolata Figure 28.7 Euglena, a euglenid commonly found in pond water. Belongs to group of ciliates

Vorticella_Chromalveolata Figure 28.7 Euglena, a euglenid commonly found in pond water. Belongs to group of ciliates

Balantidium coli_Chromalveolata Figure 28.7 Euglena, a euglenid commonly found in pond water. Belongs to group of ciliates Parasites in humans (e.g. colon) to induce ulcers

Amoeba_Unikonta (Sarcodina) Figure 28.7 Euglena, a euglenid commonly found in pond water. Movement through pseudopodia (by reversible assembly of cytoskeleton)

Radiolaria_Rhizaria (Sarcodina) Figure 28.7 Euglena, a euglenid commonly found in pond water. Marine amoebas; cytoskeleton made of silica

Foramnifera_Rhizaria (Sarcodina) Figure 28.7 Euglena, a euglenid commonly found in pond water. 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.

Prokaryotic producers Protists play key roles for ecology Other consumers Herbivorous plankton Carnivorous plankton Figure 28.27 Protists: key producers in aquatic communities. Protistan producers Prokaryotic 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.