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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
• 300 years ago, the Dutch microscopist Antoni van
Leeuwenhook stated:
• “No more pleasant sight has met my eye than so
many thousands of living things in a drop of water”
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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
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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
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• 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
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• Some protists reproduce asexually, while
others reproduce sexually, or alternate
between sexual and asexual cycles
• Eukaryotes evolved by endosymbiosis
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The Evolutionary Origins of Mitochondria
and Chloroplasts (Chapter 6)
• Mitochondria and chloroplasts have similarities
with bacteria
– Enveloped by a double membrane
– Contain free ribosomes and circular DNA
molecules
– Grow and reproduce somewhat independently
in cells
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• The Endosymbiont theory
– An early ancestor of eukaryotic cells engulfed
a nonphotosynthetic prokaryotic cell, which
formed an endosymbiont relationship with its
host
– The host cell and endosymbiont merged into
a single organism, a eukaryotic cell with a
mitochondrion
– At least one of these cells may have taken up
a photosynthetic prokaryote, becoming the
ancestor of cells that contain chloroplasts
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Figure 6.16
Endoplasmic
reticulum
Engulfing of oxygenusing nonphotosynthetic
prokaryote, which
becomes a mitochondrion
Nucleus
Nuclear
envelope
Ancestor of
eukaryotic cells
(host cell)
Mitochondrion
Nonphotosynthetic
eukaryote
At least
one cell
Engulfing of
photosynthetic
prokaryote
Chloroplast
Mitochondrion
Photosynthetic eukaryote
• 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
• Formerly 5 Kingdoms:
• Monera, Protista, Plantae, Fungi, Animalia
• Now:
• 3 Domains: Bacteria, Archae, Eukarya
© 2011 Pearson Education, Inc.
Figure 26.21
Eukarya
Land plants
Green algae
Dinoflagellates
Forams
Ciliates
Diatoms
Red algae
Cellular slime molds
Amoebas
Euglena
Trypanosomes
Leishmania
Animals
Fungi
Green
nonsulfur bacteria
Sulfolobus
Thermophiles
(Mitochondrion)
Spirochetes
Halophiles
COMMON
ANCESTOR
OF ALL
LIFE
Chlamydia
Green
sulfur bacteria
Bacteria
Methanobacterium
Archaea
Cyanobacteria
(Plastids, including
chloroplasts)
5 Supergroups of Eukaryotes
Parabasalids
Euglenozoans
Excavata
Diplomonads
Apicomplexans
Ciliates
Diatoms
Stramenopiles
Golden algae
Chromalveolata
Alveolates
Dinoflagellates
Brown algae
Oomycetes
Forams
Radiolarians
Green
algae
Chlorophytes
Charophytes
Land plants
Archaeplastida
Red algae
Rhizaria
Cercozoans
Gymnamoebas
Entamoebas
Opisthokonts
Nucleariids
Fungi
Choanoflagellates
Animals
Unikonta
Amoebozoans
Slime molds
Figure 28.7
Euglena_Excavata
Long flagellum
Eyespot
Short flagellum
Light
detector
Contractile vacuole
Nucleus
Chloroplast
Plasma membrane
Euglena (LM)
5 m
Pellicle
Mixotroph = autotroph and heterotroph
Trichonympha_Excavata
Inhabits the guts of many termite species
enabling them to digest wood (e.g. cellulose)
Trypanosome_Excavata
Parasites which causes sleeping disease in humans
Paramecium_Chromalveolata
Belongs to group of ciliates
Sexual reproduction by conjugation,
Asexual reproduction by binary fission
Stentor_Chromalveolata
Belongs to group of ciliates
Vorticella_Chromalveolata
Belongs to group of ciliates
Balantidium coli_Chromalveolata
Belongs to group of ciliates
Parasites in humans (e.g. colon) to induce ulcers
Amoeba_Unikonta (Sarcodina)
Movement through pseudopodia
(by reversible assembly of cytoskeleton)
Radiolaria_Rhizaria (Sarcodina)
Marine amoebas; cytoskeleton made of silica
Foramnifera_Rhizaria (Sarcodina)
Marine amoebas; porous shells consisting of organic
material hardened with calcium carbonate
Protists play key roles for ecology
Protists have important roles as symbionts:
• Photosynthetic dinoflagellates provide food for
coral polyps that build coral reefs
• Cellulose digesting protists in termites or
ruminants
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Protists play key roles for ecology
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.