Introduction to the Protists:
Protozoa
Introduction to the Protists:
Protozoa
1. Introduction
2. Euglenozoans
3. Alveolates
4. Amoebozoans
Protists: Very Diverse and
Successful
Introduction: The Protists
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In the past, all protists were grouped together
in the Kingdom “Protista”
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“Protist” is now used to refer to organisms that
are neither plant, animal, nor fungi
•
“Paraphyletic”: protists represent a diverse
group of organisms from many evolutionary
lineages
–
•
More structural and functional diversity than
any other group of organisms
•
Most unicellular; some colonial or multicellular
•
Single cells, but very complex
–
–
Diverse cellular functions
Very specialized organelles
Compare to “monophyletic” lineages
Introduction to Protists (cont.)
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Nutrition: autotrophs, heterotrophs,
mixotrophs
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Habitats: Most aquatic, some terrestrial;
important as plankton
•
Reproduction: some asexual, most
sexual
Cilia and Flagella
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Cilia
– Usually occurs in large numbers on cell
surface; short
– “back and forth” motion
•
Flagella
– One or a few per cell; long
– Undulatory motion
1
Cilia and Flagella: Motion
Fig 6.23
Flagella and Cilia: “9 + 2” Structure
Fig 6.24
Euglenozoans
Introduction to Protists: Protozoa
1. Introduction
•
Diverse group that contains predatory
heterotrophs, photosynthetic autotrophs,
and pathogenic parasites
•
Characterized by unique rod-like
structures in flagella
•
Some examples: Euglena, Trypanosoma
2. Euglenozoans
3. Alveolates
4. Amoebozoans
Euglena: Mixotrophic
Fig 28.8
Trypanosoma: Sleeping Sickness
Not In
Text
2
Trypanosoma: Sleeping Sickness
Introduction to Protists: Protozoa
1. Introduction
2. Euglenozoans
3. Alveolates
Fig 28.7
4. Amoebozoans
Alveolates
•
•
Characterized by membrane-bound sacs
(alveoli) just under the plasma membrane
Function of alveoli unknown
–
–
•
Alveoli: Unique Structures in Cell
Membranes of the Alveolates
May stabilize cell surface
May be involved in osmoregulation
Some examples: Paramecium, Plasmodium
Paramecium: A Ciliate
Fig 28.12
Plasmodium: Malaria
Fig 28.11
3
Amoebozoans
Introduction to Protists: Protozoa
•
Many species of amoeba have lobe-shaped
pseudopodia
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Entamoebas: Parasites that cause amebic
dysentery in humans
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Gymnamoebas: common in soil, freshwater,
and marine habitats
1. Introduction
2. Euglenozoans
3. Alveolates
–
4. Amoebozoans
Most are heterotrophs that feed on bacteria and
other protists
An Amoeba Feeding
Fig 28.24
4