Unit 5 Target III: Protist Diversity
(Ch. 25, 28.1&28.7)
Chapter 28: Protists
28.1 Most eukaryotes are single-celled organisms
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Protists are classified as eukaryotes in domain Eukarya
EUKARYOTIC AND PROKARYOTIC CELLS REVIEW:
EUKARYOTIC CELLS
Has a membrane-bound
nucleus- DNA in nucleus
BOTH
Have cytoplasm
Has cell organelles
ribosomes
nucleoid
Plasma membrane
PROKARYOTIC CELLS
Does not have a membranebound nucleus- DNA in
nucleoid
Does not have cell organelles
Structural and Functional Diversity in Protists
Protists are:
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Mostly unicellular, but some may be colonial or multicellular
Known to rely on certain organelles more than others: nucleus, endoplasmic reticulum,
Golgi apparatus, lysosomes
Photoautotrophs- contain chloroplasts to perform photosynthesis and convert light
energy into glucose for food (self-feeding)
Heterotrophs- obtain food from other organisms or absorbing organic molecules (feeds
on others)
Mixotrophs- perform both photoautotrophic and heterotrophic nutrition feeding
(Euglena)
either strictly asexual, sexual, or both!
Endosymbiosis in Eukaryotic Evolution
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There is evidence that much of protest diversity has its origins in endosymbiosis- the
process in which certain unicellular organisms engulf other cells which become
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endosymbionts, then organelles in the host cell (ex: how first eukaryotes acquired
mitochondria and plastids)
During eukaryotic evolution, red and green algae both underwent secondary
endosymbiosis; the algae became endosymbionts when they were ingested in the food
vacuole of other heterotrophic eukaryotes, seen in green algae since green algae still
carries out photosynthesis with its plastids and contains a small nucleus of its own.
28.7 Protists play key roles in ecological relationships
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Most protists are aquatic and live in aquatic environments
Many protists are producers- organisms that use energy from light or inorganic
chemicals to convert CO2 to organic compounds, and all other organisms are dependent
on them for food
Extra
Protist Supergroups!
Excavata
Diplomonads:
-Mostly anaerobic. Have mitosomes rather than mitochondria. Flagellated. Heterotrophic. Parasite.
-Ex: Giardia intestinalis
Euglenozoans:
-contains autotrophs, heterotrophs, & parasites
-spiral or crystalline rod in their flagellum
-Ex: Euglena
-Mixotrophs, engulf prey by phagocytosis, reproduce by mitosis
-Eyespot: dark organelle near flagellum. Light Detector: swelling near the base of the flagellum.
-Ex: Trypanosoma --> African Sleeping Disease
Chromalveolata
-Evolved through secondary endosymbiosis
a. Alveolates:
-Ex: dinoflagellates
-covered by cellulose plates
-Phototrophic, heterotrophic, & mixotrophic
-Red tide: bloom of algae that causes water to appear red
-Ex: Paramecium
-Ciliate, contractile vacuole expels water that enters from hypotonic environment through osmosis
-Ex: Plasmodium vivax--> malaria
b. Stramenopiles:
-Hairy flagellum & non-hairy flagellum
-autotrophs & heterotrophs
-Ex: diatoms
-appear glass-like b/c of silica
-Photosynthetic
Rhizaria
-Move by pseudopodia. Heterotrophic.
Archeplastidia
-evolved from an ancient protist that engulfed a cyanobacterium
-Ex: red algae
-Ex: green algae
-unicellular, colonial, & multicellular
-Ex: volvox
Unikonta
a. Amoebozoans
-oval tube shaped pseududopodia
-Ex: Amoeba
b. Opisthokonts
-animal-like and fungi-like protists