Albia Dugger • Miami Dade College

Cecie StarrChristine EversLisa Starr

www.cengage.com/biology/starr

Chapter 20The Protists(Sections 20.1 - 20.4)

20.1 Harmful Algal Blooms

• Aquatic protists include single-celled and multicellular autotrophs and heterotrophs

• An algal bloom is a population explosion of an aquatic protist, or of another aquatic microorganism

• Toxins released during some algal blooms can harm wildlife and endanger human health

Key Terms

• protist • Eukaryote that is not a fungus, animal, or plant

• algal bloom • Population explosion of tiny aquatic producers

• toxin • Chemical that is made by one organism and harms

another

Karenia brevis

• This dinoflagellate produces brevetoxin, which interferes with nerve cells of people and animals who inhale or ingest it

20.2 A Collection of Lineages

• Protists are a collection of mostly single-celled eukaryotes

• Many have chloroplasts that evolved from cyanobacteria or another protist

• The dominant stage of the life cycle may be haploid or diploid

• Protists are not a natural group, but a collection of lineages, some only distantly related to one another

Protist Diversity

Fig. 20.2a, p. 312

Protist Diversity

Fig. 20.2b, p. 312

Protist Diversity

Fig. 20.2c, p. 312

Protist Diversity

Fig. 20.2d, p. 312

Protist Diversity

Fig. 20.2e, p. 312

Protist Diversity

Protist Groups

• Protists are not a single lineage

• One proposed eukaryotic family tree with protist groups indicated by tan boxes

Fig. 20.2f, p. 312

ancestral cells

Amoebozoans

Stramenopiles

Flagellated Protozoans

Alveolates

Green Algae

fungi

slime moldsamoebas

land plantscharophyte algaechlorophyte algae

red algae

brown algaediatomswater molds

apicomplexans

dinoflagellatesciliates

foraminiferansradiolarians

euglenoidstrypanosomesparabasalidsdiplomonads

animalschoanoflagellates

F

Protist Groups

Key Concepts

• A Collection of Lineages • Protists include many lineages of eukaryotic organisms,

some autotrophs and others heterotrophs• Protists are not a clade; some groups are more closely

related to plants, or to fungi and animals, than to other protists

20.3 Flagellated Protozoans

• Flagellated protozoans are single cells with no cell wall – a protein covering (pellicle) helps maintain the cell’s shape

• flagellated protozoan • Protist belonging to an entirely or mostly heterotrophic

lineage with no cell wall and one or more flagella

• pellicle • Layer of proteins that gives shape to many unwalled,

single-celled protists

Diplomonads and Parabasalids

• Diplomonads and parabasalids have multiple flagella and are adapted to oxygen-poor habitats

• Instead of mitochondria, they have organelles that produce ATP by an anaerobic pathway

• Both groups include species that infect humans

A Diplomonad

• Diplomonads have two more or less identical nuclei

• Giardia lamblia causes giardiasis, a waterborne intestinal disease

A Parabasalid

• Trichomonas vaginalis causes a sexually transmitted disease

Trypanosomes

• trypanosome • Parasitic flagellate with a

single mitochondrion and a membrane-encased flagellum

• Insects transmit trypanosomes, such as Trypanosoma brucei, which causes African sleeping sickness

Euglenoids

• euglenoid • Flagellated protozoan with multiple mitochondria• Some have chloroplasts that evolved by secondary

endosymbiosis from a green alga• Typically live in fresh water• Have a contractile vacuole

• contractile vacuole • In freshwater protists, an organelle that collects and expels

excess water

Body Plan of Euglena

Fig. 20.4, p. 313

nucleus

long flagellum

contractile vacuole

pellicle Golgi body mitochondrion

ER

eyespot

chloroplast

Body Plan of Euglena

ANIMATION: Body plan of Euglena

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20.4 Mineral-Shelled Protozoans

• Foraminiferans and radiolarians are single-celled marine protists with sieve-like shells

• They capture food with microtubule-reinforced cytoplasmic extensions that protrude through the shell’s openings

• Both are marine heterotrophs and may be part of plankton

• plankton • Community of tiny drifting or swimming organisms

Foraminiferans and Radiolarians

• foraminiferan • Heterotrophic single-celled protist with a chalky calcium

carbonate shell and long cytoplasmic extensions• Deposits of their remains are mined for chalk and

limestone

• radiolarian • Heterotrophic single-celled protist with a glassy silica shell

and long cytoplasmic extensions that stick out through the porous shell and capture prey

Foraminiferans and Radiolarians

Fig. 20.5a, p. 314

Foraminiferans and Radiolarians

Fig. 20.5b, p. 314

Foraminiferans and Radiolarians

Fig. 20.5c, p. 314

Foraminiferans and Radiolarians