Protists

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Slide 1

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 kingdom of mostly unicellular eukaryotes, but there are some colonial and multicellular species.

Protists constitute a paraphyletic group, and Protista is no longer valid as a kingdom.

Protists exhibit more structural and functional diversity than any other group of eukaryotes.

Slide 2

Protists can reproduce asexually or sexually, or by the sexual processes of meiosis and syngamy.

Protists, the most nutritionally diverse of all eukaryotes, include:

Photoautotrophs - contain chloroplasts.

Heterotrophs - absorb organic molecules or ingest larger food particles.

Mixotrophs - combine photosynthesis and heterotrophic nutrition.

Slide 3

Endosymbiosis in Eukaryotic Evolution

There is considerable evidence that much protist diversity has its origins in endosymbiosis.

Mitochondria evolved by endosymbiosis of an aerobic prokaryote.

Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium.

Slide 4

Endosymbiosis --> Eukaryotic Evolution

Cyanobacterium

Heterotrophic

eukaryote

Over the course

of evolution,

this membrane

was lost.

Red alga

Green alga

Primary

endosymbiosis

Secondary

endosymbiosis

Secondary

endosymbiosis

Secondary

endosymbiosis

Plastid

Dinoflagellates

Apicomplexans

Stramenopiles

Plastid

Euglenids

Chlorarachniophytes

Slide 5

Protist Diversity

Green

algae

Amoebozoans

Opisthokonts

Alveolates

Stramenopiles

Diplomonads

Parabasalids

Euglenozoans

Dinoflagellates

Apicomplexans

Ciliates

Diatoms

Golden algae

Brown algae

Oomycetes

Excavata

Chromalveolata

Rhizaria

Chlorarachniophytes

Forams

Radiolarians

Archaeplastida

Red algae

Chlorophytes

Charophyceans

Land plants

Unikonta

Slime molds

Gymnamoebas

Entamoebas

Nucleariids

Fungi

Choanoflagellates

Animals

Slide 6

Protist Diversity - Diplomonads intestinal parasites

5 µm

Slide 7

Diatoms - unicellular algae / cell walls are glass-like and made of silica

50 µm

Slide 8