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Biology Concepts and Applications | 9e

Starr | Evers | Starr

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Chapter 20

The Protists

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What Are Protists?

• Protists are not a natural

group, but a collection of

lineages, some only

distantly related to one

another; many have

chloroplasts

• Past classification was

Kingdom Protista

• Current classification is

still being sorted out

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Protists: A collection of mostly single-

celled eukaryotes.

Animal-like protists

(Heterotrophs)

Fungus-like protists

(Absorptive) Plant-like protists

(Autotrophs)

Clade – a group whose members share one or more

defining traits (e.g. flagella, shells, pigment type, etc.)

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Clade Excavata

Giardia intestinalis –

waterborne parasite

Trypanosoma –

parasite that causes

sleeping sickness

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Clade Rhizaria

Foraminiferans have tests (shells) made of

calcium carbonate and threadlike

pseudopodia

Living foraminiferan Fossilized foraminiferan

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Clade Alveolata

Apicomplexan in blood cells

Apicomplexans are parasitic, reproduce only in

host cells. Ex: Plasmodium is an

apicomplexan that causes malaria.

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Clade Alveolata

Dinoflagellates: paired flagella in

perpendicular grooves make them

spin.

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Clade Alveolata: Dinoflagellates

Most common source of bioluminescence

– light produced by a living organism

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Clade Alveolata: Dinoflagellates

Can also cause algal blooms, aka “red

tides”, some of which can be harmful

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Clade Stramenopila

• Brown algae are multicellular, mostly

marine, ex: giant kelp

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Clade Amoebozoa

• Ameobas move and feed using lobe-

shaped pseudopodia

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Clade Amoebozoa

• Plasmodial slime molds form a plasmodium

(one big cell with many nuclei); common on the

floor of temperate forests.

Plasmodial slime mold streaming across log.

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Clade Amoebozoa

• Cellular slime molds exist as individual

amoeba-like cells. When food runs low, can

stream together to form a multicelled unit

Cellular slime mold on forest floor.

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Clade Archaeplastida

• Red algae are photosynthetic, multicelled;

grow at greater depths than green algae.

Many commercial uses

including agar, carrageenan

and nori sushi wrap

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Clade Archaeplastida

• Green algae are most closely related to land

plants; uses chlorophyll for photosynthesis; may

be single celled, colonial, or multicelled.