Chapter 28—Protists

DomainBacteria

DomainArchaea

DomainEukarya

Common ancestor

Kingdom: Protists

Domain Eukarya

I. Introduction to the Protists

• Classification criteria

– eukaryotes

– not animal, plant or fungi

Great Diversity

din

oflag

ella

tes

& c

ilia

tes

eugle

noid

s

bro

wn a

lgae

& d

iato

ms

red a

lgae

gre

en a

lgae

mis

cella

neous?

Problems with Protist

Classification

Euglenozo

a

Anim

als

Strep

tophyt

a

(incl

udes la

nd pla

nts)

Choan

oflagel

lida

Fungi

Chlo

rophyt

a

Rhodophyt

a

Stram

enopila

Alv

eola

ta

Arc

haea

Bac

teria

• Too Diverse!– doesn’t reflect any evolutionary relationship among all

kingdom members

– paraphyletic

II.Origin/Diversification of Eukaryotes

Ancestral eukaryotic cell Eukaryotic cell withmitochondrion

internal membrane system

aerobic bacterium

mitochondrion

chloroplast

Eukaryotic cell with chloroplasts

photosyntheticbacterium

Paramecium & symbiont Chlorella

Endosymbiotic Theory

III. Protist Diversity• The full spectrum of modes of life

– from unicellular to multicellular

– Autotrophic to heterotrophic• Can be mixotrophic

– asexual to sexual reproduction

– pathogenic to beneficial

– sessile to mobile

Mobility

• How Protists move

– flagella

– cilia

– pseudopodia

• Animal-like Protists– heterotrophs, predators

• Amoeba

• Paramecium

• Stentor

Paramecium with food vacuoles stained red

Amoeba ingesting a Paramecium

• Plant-like Protists

– autotrophs, photosynthesis

• Euglena

• algae

• diatoms

• Parasitic & pathogenic Protists– Plasmodium (malaria)

– Giardia

– Trypanosoma

Plasmodium

Giardia

Trypanosoma

• Beneficial & necessary Protists

– phytoplankton

• small algae + diatoms

• much of the world’s photosynthesis

• produces ~90% of atmospheric oxygen

– zooplankton

• heterotrophic protists + animals

• key ecological role at base of

marine food web

Mmmmmm!

Sounds like breakfast!