LECTURE PRESENTATIONS For CAMPBELL BIOLOGY, NINTH EDITION Jane
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 Protist is the informal name of the group of mostly unicellular eukaryotes 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caused the classification of protists to change significantly Protists constitute a polyphyletic group, and Protista is no longer valid as a kingdom 2011 Pearson Education, Inc. Figure 28.1 1 m Concept 28.1: Most eukaryotes are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 by the sexual processes of meiosis and fertilization 2011 Pearson Education, Inc. Endosymbiosis in Eukaryotic Evolution There is now considerable evidence that much protist diversity has its origins in endosymbiosis Endosymbiosis is the process in which a unicellular organism engulfs another cell, which becomes an endosymbiont and then organelle in the host cell Mitochondria evolved by endosymbiosis of an aerobic prokaryote Plastids evolved by endosymbiosis of a
photosynthetic cyanobacterium 2011 Pearson Education, Inc. Figure 28.2 Plastid Dinoflagellates Membranes are represented as dark lines in the cell. Secondary endosymbiosis
The plastid-bearing lineage of protists evolved into red and green algae The DNA of plastid genes in red algae and green algae closely resemble the DNA of cyanobacteria On several occasions during eukaryotic evolution, red and green algae underwent secondary endosymbiosis, in which they were ingested by a heterotrophic eukaryote 2011 Pearson Education, Inc. Five Supergroups of Eukaryotes It is no longer thought that amitochondriates (lacking mitochondria) are the oldest lineage of
eukaryotes Many have been shown to have mitochondria and have been reclassified Our understanding of the relationships among protist groups continues to change rapidly One hypothesis divides all eukaryotes (including protists) into five supergroups 2011 Pearson Education, Inc. Figure 28.3a Parabasalids Euglenozoans
Excavata Diplomonads Apicomplexans Ciliates Diatoms Stramenopiles Golden algae Brown algae Chromalveolata
Alveolates Dinoflagellates Oomycetes Forams Radiolarians Green algae Chlorophytes Charophytes Land plants
Archaeplastida Red algae Rhizaria Cercozoans Gymnamoebas Entamoebas Opisthokonts Nucleariids
5 m Giardia intestinalis, a diplomonad parasite Figure 28.3c 50 m Diatom diversity Figure 28.3d 100 m
Globigerina, a foram in the supergroup Rhizaria Figure 28.3e 20 m 50 m Volvox, a colonial freshwater green alga Figure 28.3f 100 m A unikont amoeba
Concept 28.2: Excavates include protists with modified mitochondria and protists with unique flagella The clade Excavata is characterized by its cytoskeleton Some members have a feeding groove This controversial group includes the diplomonads, parabasalids, and euglenozoans 2011 Pearson Education, Inc. Figure 28.UN01 Parabasalids
Kinetoplastids Euglenozoans Euglenids Excavata Diplomonads Chromalveolata Rhizaria Archaeplastida Unikonta Diplomonads and Parabasalids These two groups lack plastids, have modified
mitochondria, and most live in anaerobic environments Diplomonads Have modified mitochondria called mitosomes Derive energy from anaerobic biochemical pathways Have two equal-sized nuclei and multiple flagella Are often parasites, for example, Giardia intestinalis (also known as Giardia lamblia) 2011 Pearson Education, Inc. Parabasalids Have reduced mitochondria called hydrogenosomes that generate some energy
anaerobically Include Trichomonas vaginalis, the pathogen that causes yeast infections in human females 2011 Pearson Education, Inc. Figure 28.4 5 m Flagella Undulating membrane
Euglenozoans Euglenozoa is a diverse clade that includes predatory heterotrophs, photosynthetic autotrophs, and parasites The main feature distinguishing them as a clade is a spiral or crystalline rod of unknown function inside their flagella This clade includes the kinetoplastids and euglenids 2011 Pearson Education, Inc. Figure 28.5 Flagella
0.2 m 8 m Crystalline rod (cross section) Ring of microtubules (cross section) Kinetoplastids Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast They include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems
This group includes Trypanosoma, which causes sleeping sickness in humans Another pathogenic trypanosome causes Chagas disease 2011 Pearson Education, Inc. Figure 28.6 9 m Trypanosomes evade immune responses by switching surface proteins A cell produces millions of copies of a single protein
The new generation produces millions of copies of a different protein These frequent changes prevent the host from developing immunity 2011 Pearson Education, Inc. Euglenids Euglenids have one or two flagella that emerge from a pocket at one end of the cell Some species can be both autotrophic and heterotrophic 2011 Pearson Education, Inc.
Figure 28.7 Long flagellum Eyespot Short flagellum Contractile vacuole Light detector Nucleus Chloroplast Plasma membrane Euglena (LM)
5 m Pellicle Figure 28.7a Long flagellum Eyespot Contractile vacuole Nucleus Chloroplast Plasma membrane Euglena (LM)
5 m Concept 28.3: Chromalveolates may have originated by secondary endosymbiosis Some data suggest that the clade Chromalveolata is monophyletic and originated by a secondary endosymbiosis event The proposed endosymbiont is a red alga This clade is controversial and includes the alveolates and the stramenopiles 2011 Pearson Education, Inc. Figure 28.UN02
Excavata Dinoflagellates Diatoms Golden algae Brown algae Oomycetes Stramenopiles Chromalveolata Apicomplexans Alveolates Ciliates
Rhizaria Archaeplastida Unikonta Alveolates Members of the clade Alveolata have membrane-bounded sacs (alveoli) just under the plasma membrane The function of the alveoli is unknown The alveolates include Dinoflagellates Apicomplexans Ciliates
2011 Pearson Education, Inc. Figure 28.8 Alveoli Alveolate 0.2 m Flagellum Figure 28.8a Alveoli
0.2 m Flagellum Dinoflagellates Dinoflagellates have two flagella and each cell is reinforced by cellulose plates They are abundant components of both marine and freshwater phytoplankton They are a diverse group of aquatic phototrophs, mixotrophs, and heterotrophs Toxic red tides are caused by dinoflagellate blooms 2011 Pearson Education, Inc.
Figure 28.9 3 m Flagella Apicomplexans Apicomplexans are parasites of animals, and some cause serious human diseases They spread through their host as infectious cells called sporozoites One end, the apex, contains a complex of organelles specialized for penetrating host cells and tissues
Most have sexual and asexual stages that require two or more different host species for completion 2011 Pearson Education, Inc. The apicomplexan Plasmodium is the parasite that causes malaria Plasmodium requires both mosquitoes and humans to complete its life cycle Approximately 900,000 people die each year from malaria Efforts are ongoing to develop vaccines that target this pathogen 2011 Pearson Education, Inc.
Figure 28.10-1 Inside human Merozoite Liver Liver cell Apex Red blood cell Merozoite (n)
0.5 m Red blood cells Gametocytes (n) Key Haploid (n) Diploid (2n) Figure 28.10-2
Inside mosquito Inside human Merozoite Liver Liver cell Apex Red blood cell Merozoite (n) Zygote
(2n) 0.5 m Red blood cells FERTILIZATION Gametes Gametocytes (n) Key
0.5 m Red blood cells FERTILIZATION Gametes Gametocytes (n) Key Haploid (n) Diploid (2n)
Figure 28.10a Merozoite Apex Red blood cell 0.5 m Ciliates Ciliates, a large varied group of protists, are named for their use of cilia to move and feed They have large macronuclei and small
micronuclei Genetic variation results from conjugation, in which two individuals exchange haploid micronuclei Conjugation is a sexual process, and is separate from reproduction, which generally occurs by binary fission 2011 Pearson Education, Inc. Figure 28.11 Contractile vacuole 50 m Oral groove
Cell mouth Cilia Micronucleus Food vacuoles Macronucleus (a) Feeding, waste removal, and water balance Key Conjugation Asexual reproduction
MEIOSIS Compatible mates Diploid micronucleus Haploid micronucleus Diploid The original macronucleus micronucleus
disintegrates. MICRONUCLEAR FUSION (b) Conjugation and reproduction Figure 28.11a Oral groove Contractile vacuole 50 m Cell mouth Cilia
Micronucleus Macronucleus Food vacuoles (a) Feeding, waste removal, and water balance Figure 28.11b-1 Compatible mates MEIOSIS Diploid micronucleus
MEIOSIS Diploid micronucleus Haploid micronucleus Diploid The original macronucleus micronucleus disintegrates. MICRONUCLEAR FUSION
Key (b) Conjugation and reproduction Conjugation Asexual reproduction Figure 28.11c 50 m Stramenopiles The clade Stramenopila includes important phototrophs as well as several clades of
heterotrophs Most have a hairy flagellum paired with a smooth flagellum Stramenopiles include diatoms, golden algae, brown algae, and oomycetes 2011 Pearson Education, Inc. Figure 28.12 Hairy flagellum Smooth flagellum
5 m Diatoms Diatoms are unicellular algae with a unique twopart, glass-like wall of hydrated silica Diatoms usually reproduce asexually, and occasionally sexually 2011 Pearson Education, Inc. 40 m Figure 28.13 Diatoms are a major component of phytoplankton and are highly diverse
Fossilized diatom walls compose much of the sediments known as diatomaceous earth After a diatom population has bloomed, many dead individuals fall to the ocean floor undecomposed 2011 Pearson Education, Inc. This removes carbon dioxide from the atmosphere and pumps it to the ocean floor 2011 Pearson Education, Inc. Golden Algae Golden algae are named for their color, which results from their yellow and brown carotenoids
The cells of golden algae are typically biflagellated, with both flagella near one end All golden algae are photosynthetic, and some are mixotrophs Most are unicellular, but some are colonial 2011 Pearson Education, Inc. Figure 28.14 Flagellum Outer container Living cell 25 m
Brown Algae Brown algae are the largest and most complex algae All are multicellular, and most are marine Brown algae include many species commonly called seaweeds Brown algae have the most complex multicellular anatomy of all algae 2011 Pearson Education, Inc. Giant seaweeds called kelps live in deep parts of the ocean The algal body is plantlike but lacks true roots,
stems, and leaves and is called a thallus The rootlike holdfast anchors the stemlike stipe, which in turn supports the leaflike blades 2011 Pearson Education, Inc. Figure 28.15 Blade Stipe Holdfast Alternation of Generations
A variety of life cycles have evolved among the multicellular algae The most complex life cycles include an alternation of generations, the alternation of multicellular haploid and diploid forms Heteromorphic generations are structurally different, while isomorphic generations look similar 2011 Pearson Education, Inc. The diploid sporophyte produces haploid flagellated spores called zoospores The zoospores develop into haploid male and female gametophytes, which produce gametes
Fertilization of gamates results in a diploid zygote, which grows into a new sporophyte 2011 Pearson Education, Inc. Figure 28.16-1 Key Haploid (n) Diploid (2n) Sporangia 10 cm Sporophyte
Sperm Figure 28.16a 10 cm Oomycetes (Water Molds and Their Relatives) Oomycetes include water molds, white rusts, and downy mildews They were once considered fungi based on morphological studies Most oomycetes are decomposers or parasites They have filaments (hyphae) that facilitate nutrient uptake
Their ecological impact can be great, as in potato blight caused by Phytophthora infestans 2011 Pearson Education, Inc. Figure 28.17-1 Germ tube Cyst Hyphae ASEXUAL REPRODUCTION Zoospore
Figure 28.17a Concept 28.4: Rhizarians are a diverse group of protists defined by DNA similarities DNA evidence supports Rhizaria as a monophyletic clade Amoebas move and feed by pseudopodia; some but not all belong to the clade Rhizaria Rhizarians include radiolarians, forams, and cercozoans 2011 Pearson Education, Inc. Figure 28.UN03
Excavata Chromalveolata Rhizaria Radiolarians Foraminiferans Cercozoans Archaeplastida Unikonta Radiolarians Marine protists called radiolarians have tests
fused into one delicate piece, usually made of silica Radiolarians use their pseudopodia to engulf microorganisms through phagocytosis The pseudopodia of radiolarians radiate from the central body 2011 Pearson Education, Inc. Figure 28.18 Pseudopodia 200 m Forams
Foraminiferans, or forams, are named for porous, generally multichambered shells, called tests Pseudopodia extend through the pores in the test Foram tests in marine sediments form an extensive fossil record Many forams have endosymbiotic algae 2011 Pearson Education, Inc. Cercozoans Cercozoans include most amoeboid and flagellated protists with threadlike pseudopodia They are common in marine, freshwater, and soil ecosystems
Most are heteroptrophs, including parasites and predators 2011 Pearson Education, Inc. Paulinella chromatophora is an autotroph with a unique photosynthetic structure This structure evolved from a different cyanobacterium than the plastids of other photosynthetic eukaryotes 2011 Pearson Education, Inc. Figure 28.19
Chromatophore 5 m Concept 28.5: Red algae and green algae are the closest relatives of land plants Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont The photosynthetic descendants of this ancient protist evolved into red algae and green algae Land plants are descended from the green algae Archaeplastida is the supergroup that includes red algae, green algae, and land plants 2011 Pearson Education, Inc.
Figure 28.UN04 Excavata Chromalveolata Rhizaria Chlorophytes Charophytes Green algae Land plants Archaeplastida
Red algae Unikonta Red Algae Red algae are reddish in color due to an accessory pigment called phycoerythrin, which masks the green of chlorophyll The color varies from greenish-red in shallow water to dark red or almost black in deep water Red algae are usually multicellular; the largest are seaweeds Red algae are the most abundant large algae in coastal waters of the tropics
2011 Pearson Education, Inc. Figure 28.20 Bonnemaisonia hamifera 20 cm 8 mm Dulse (Palmaria palmata) Nori Green Algae
Green algae are named for their grass-green chloroplasts Plants are descended from the green algae Green algae are a paraphyletic group The two main groups are chlorophytes and charophyceans Charophytes are most closely related to land plants 2011 Pearson Education, Inc. Most chlorophytes live in fresh water, although many are marine Other chlorophytes live in damp soil, as symbionts in lichens, or in snow
2011 Pearson Education, Inc. Larger size and greater complexity evolved in chlorophytes by 1. The formation of colonies from individual cells 2. The formation of true multicellular bodies by cell division and differentiation (e.g., Ulva) 3. The repeated division of nuclei with no cytoplasmic division (e.g., Caulerpa) 2011 Pearson Education, Inc.
Figure 28.21 2 cm (b) Caulerpa, an intertidal chlorophyte (a) Ulva, or sea lettuce Most chlorophytes have complex life cycles with both sexual and asexual reproductive stages 2011 Pearson Education, Inc.
MEIOSIS Figure 28.22b Flagella 1 m Cell wall Nucleus Cross section of
cup-shaped chloroplast (TEM) Concept 28.6: Unikonts include protists that are closely related to fungi and animals The supergroup Unikonta includes animals, fungi, and some protists This group includes two clades: the amoebozoans and the opisthokonts (animals, fungi, and related protists) The root of the eukaryotic tree remains controversial It is unclear whether unikonts separated from
other eukaryotes relatively early or late 2011 Pearson Education, Inc. Figure 28.UN05 Excavata Chromalveolata Rhizaria Archaeplastida Amoebozoans Unikonta Nucleariids Fungi
Choanoflagellates Animals Figure 28.23 RESULTS Choanoflagellates Animals Fungl Common ancestor of all eukaryotes
Rhizarians Rhizaria Red algae Green algae Plants Archaeplastida Amoebozoans Amoebozoans are amoeba that have lobe- or tube-shaped, rather than threadlike, pseudopodia They include slime molds, gymnamoebas, and
entamoebas 2011 Pearson Education, Inc. Slime Molds Slime molds, or mycetozoans, were once thought to be fungi Molecular systematics places slime molds in the clade Amoebozoa 2011 Pearson Education, Inc. Plasmodial Slime Molds Many species of plasmodial slime molds are brightly pigmented, usually yellow or orange
2011 Pearson Education, Inc. Figure 28.24 4 cm FERTILIZATION Zygote (2n) Feeding plasmodium Mature plasmodium
(preparing to fruit) Flagellated cells (n) Young sporangium Amoeboid cells (n) Germinating spore Spores
(preparing to fruit) Flagellated cells (n) Young sporangium Amoeboid cells (n) Germinating spore Spores
(n) Mature sporangium MEIOSIS Key Haploid (n) Diploid (2n) Stalk At one point in the life cycle, plasmodial slime molds form a mass called a plasmodium (not to
be confused with malarial Plasmodium) The plasmodium is not multicellular It is undivided by plasma membranes and contains many diploid nuclei It extends pseudopodia through decomposing material, engulfing food by phagocytosis 2011 Pearson Education, Inc. Cellular Slime Molds Cellular slime molds form multicellular aggregates in which cells are separated by their membranes Cells feed individually, but can aggregate to form a fruiting body
Dictyostelium discoideum is an experimental model for studying the evolution of multicellularity 2011 Pearson Education, Inc. Figure 28.25-1 Spores (n) Emerging amoeba (n) Solitary amoebas (n)
600 m Fruiting bodies (n) ASEXUAL REPRODUCTION Aggregated amoebas Migrating aggregate 200 m Key
600 m Figure 28.25b 200 m Gymnamoebas Gymnamoebas are common unicellular amoebozoans in soil as well as freshwater and marine environments Most gymnamoebas are heterotrophic and actively seek and consume bacteria and other protists 2011 Pearson Education, Inc.
Entamoebas Entamoebas are parasites of vertebrates and some invertebrates Entamoeba histolytica causes amebic dysentery, the third-leading cause of human death due to eukaryotic parasites 2011 Pearson Education, Inc. Opisthokonts Opisthokonts include animals, fungi, and several groups of protists 2011 Pearson Education, Inc.
Concept 28.7: Protists play key roles in ecological communities Protists are found in diverse aquatic environments Protists often play the role of symbiont or producer 2011 Pearson Education, Inc. Symbiotic Protists Some protist symbionts benefit their hosts Dinoflagellates nourish coral polyps that build reefs Wood-digesting protists digest cellulose in the gut of termites
2011 Pearson Education, Inc. 10 m Figure 28.26 Some protists are parasitic Plasmodium causes malaria Pfiesteria shumwayae is a dinoflagellate that causes fish kills Phytophthora ramorum causes sudden oak death 2011 Pearson Education, Inc. Photosynthetic Protists
Many protists are important producers that obtain energy from the sun In aquatic environments, photosynthetic protists and prokaryotes are the main producers In aquatic environments, photosynthetic protists are limited by nutrients These populations can explode when limiting nutrients are added 2011 Pearson Education, Inc. Figure 28.27 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. Figure 28.28 Growth Growth Higher SST Lower SST In regions between the black lines, a layer of warm water
rests on top of colder waters. In the yellow regions, high SSTs increase the temperature differences between warm and cold waters, which reduces upwelling. Figure 28.UN06 Figure 28.UN06a Figure 28.UN06b
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