Randa, Bio 103
Chapter 28 / selected Protists
I. Introduction
A. Eukaryotes
1. 1st eukaryotic organisms
2. most are unicellular
3. considered simple
B. Protist diversity
1. comprised of:
a. protozoans--heterotrophs
free-living or symbiotic
b. slime molds
} saprotrophs
c. water molds
d. algae—autotrophs
2. polyphyletic kingdom
C. Protist life-styles
1. all require moist/wet environments
2. many are aquatic—plankton
3. many are motile
4. reproduce asexually (most also sexually)
II. Algae: The Plant-like Protists
A. Characteristics
1. can have chlorophyll a and b, c, or d
2. possess accessory pigments
e.g., carotenoids, phycobillins
3. size range: microscopic to macroscopic
B. Dissimilarities to plants
1. lack cuticle, true roots, stems, and leaves
2. lack true gametangia--reproductive organ surrounded by extra layer of nonreproductive cells
III. Algal Taxonomy and Diversity
A. Clade Alveolata—Dinoflagellates
1. unicellular or colonial
2. 2 flagella
3. cellulose shells
4. many autotrophic: may be endosymbionts with coral and mollusks
5. some cause red tides--release paralytic toxins
B. Clade Stramenopila—Bacillariophytes / Diatoms
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1. unicellular or colonial
2. 2 part silica shell
3. most autotrophic
4. yield diatomaceous earth
5. plankton--important in Arctic/Antarctic food chain
C. Clade Euglenozoa—Clade Euglenophyta
1. unicellular; freshwater
2. 1 exposed flagellum, other in reservoir
3. some heterotrophs, some autotrophs
4. Euglena: chloroplasts, eye spot (stigma), paramylon granules
5. has flexible pellicle
6. increase with eutrophication
D. Clade Chlorophyta--the green algae
1. very diverse: include unicellular, colonial, multicellular forms
2. some characteristics similar to plants
e.g., photosynthetic pigments: chlorophyll a and b and carotenoids
cellulose in cell walls
similar mitotic division (some)
3. flagellated cells at some point in life
4. aquatic or terrestrial
5. sexual reproduction:
isogamous, anisogamous, oogamous
E. Clade Strameopila—Clade Phaeophyta--the brown algae
1. marine; mainly cooler waters
2. chlorophyll a and c and carotenoids
3. large multicellular (kelp) have specialized body parts: blade, stipe, holdfast, float
F. Clade Stramenopila, Clade Chrysophyta--golden algae
1. colonial (some unicellular), 2 flagella per cell
2. important component of freshwater plankton
3. chlorophyll a and c and carotenoids and xanthophylls
G. Clade Rhodophyta--red algae
1. most marine (warmer waters)
2. multicellular, no motile cells
3. contain phycoerythrin and phycocyanin; chlorophyll a and d
4. used to make agar, carrageenan
IV. Slime and Water Molds: The Fungal-like Protists
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--similar to fungi in lifestyle (saprophytic) and appearance
--dissimilar to fungi by possession of:
flagellated cells
centrioles
cellulose in cell wall
A. Clade Amoebozoa--Clade Myxogastrida
plasmodium: can creep like amoeba
Reproduction: sporangia→haploid spores→
swarm cell or myxamoeba→zygote→
plasmodium
B. Clade Amoebozoa-Clade Dictylostelida
feeding stage: single, haploid amoeboid cell
can aggregate→pseudoplasmodium (slug) →
spores
C. Clade Stramenopila—Clade Oomycota--water molds
produce flagellated cells at 1 point in life cycle
like fungi, form mycelium; cell walls may contain chitin
Reproduction: asexual (favorable conditions)
sexual--oospores (less favorable conditions)
Some are important pathogens.