Protists

Front 1

Protist Lifestyles

Back 1

-decomposers
-ingestive
-parasitism/absorptive
-photosynthetic symbionts
-photosynthetic & free living

Front 2

Slime mold

Back 2

There are several unrelated monophyletic groups of slime molds
– Body form features amoeboid pseudopods (false feet)
– Often bright colored
– Live in cool, shady, moist areas
• Non-reproductive phase
– plasmodium (plural = plasmodia) formation
– plasmodia are large multinucleate masses of streaming protoplasm which moves in amoeboid fashion
– moves and engulfs bacteria, yeast, fungal spores, and small particles of decaying animals & plants
• Reproductive
– when food is in short supply, plasmodia creep to exposed location and develop stalks with sporangium from which spores are borne

Front 3

Water Molds and Downy Mildews in the Stramenopiles group

Back 3

• Saprolegnia (fly fungus) is a water mold in the Stramenopiles group
• Aquatic saprobe that is not photosynthetic
• Forms many fine threadlike hyphae which appear as a white fuzzy growth on the bodies of the dead insects and fish
• Other species in the Stramenopiles group can cause downy mildew that damages terrestrial crops

Front 4

Haploid (1n)

Back 4

-Haploid cells (1n) contain one copy of each chromosome
-Haploid phase is a gametophyte
-Gametophytes produce gametes (reproductive cells) that must fuse into other gametes before growing into new diploid individuals

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Diploid (2n)

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-Contain two copies of each chromosome
-Diploid phase is a sporophyte
-Cells in the reproductive structure of the diploid sporophyte undergo meiosis & produce haploid spores
-Spore is a reproductive cell that grows into a new individual directly through mitotic division

Front 6

Alternation of Generations

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• Haploid Spores are produced by meiosis from diploid sporophyte
• Spores germinate and divide mitotically to produce a multicellular haploid gametophyte which produces gametes by mitosis
• Gametes are mature sexual reproductive cells produced by mitosis from haploid gametophyte
• Syngamy is when two gametes fuse
• Haploid organism, diploid organism, or both may also reproduce asexually

Front 7

Heteromorphic Alternation of
Generations with Dominant Haploid Gametophyte

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• Bryophytes (liverworts, hornworts, & mosses)
–Small sporophyte is dependent on a larger dominant gametophyte

Front 8

Heteromorphic Alternation of Generations with Dominant Diploid Sporophyte

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Haploid gametophyte not dependent on dominant sporophyte:
– Brown algae kelp (Laminaria)
– Pteridophytes (seedless tracheophytes)

Front 9

Heteromorphic Alternation of Generations with Dominant Diploid Sporophyte

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Very reduced, tiny, short-lived haploid gametophyte dependent on sporophyte:
–Gymnosperms (seed tracheophytes)
– Angiosperms (seed/flower tracheophytes)

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What color Algae has what chlorophyll/phycobilins?

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All have Chlorophyll A
- Green Algae has Chlorophyll B
- Brown Algae has Chlorophyll C
- Red Algae has Phycobilins

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Brown Algae

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• mostly marine kelp & seaweeds
• the body (thallus) comes in variety of forms and may be branched
• thallus includes a holdfast, stipe, blade, and bladder (enlarged hollow structure at tip of blade)
• the holdfast is cemented to a rock with the alginates that are contained in the thallus cell walls
• alginates are used as food stabilizers/emulsifiers, in dental impression materials, and as a gel in some pharmaceutical preparations
• alginates are commercially derived from the giant brown algae kelp, Macrocystis, which grows 100 meters in length off the California coast
• Macrocystis kelp and Laminaria life cycles demonstrate heteromorphic alternation of generations with a dominant diploid sporophyte phase

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Red Algae (Rhodophytes)

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• also contain phycoerythrin and phycocyanin
• predominantly marine algae, but some fresh water
species as well
• most are multicellular and macroscopic
• agar and carrageenan are mucilaginous polysaccharides
found in cell walls
• agar is extracted from a variety of species of red algae and is used as a food stabilizer/emulsifier and as solidifying agent in culture media to grow a spectrum of different microorganisms
• carrageenan is extracted from the red algae, Irish “moss” (Chondrus crispus) and is used as a food stabilizer/emulsifier
• nori is from the red algae, Porphyra, which has been
cultivated in Japan & China for centuries as a food

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Green Algae

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• Probable precursor to vascular land plants
• Contains chlorophylls A & B which are identical to those found in vascular land plants
• Size is microscopic to several hundred feet in length
• Most are aquatic
• Some are terrestrial
• Some are symbiotic with lichens, protozoa, & invertebrates
• Some grow on the surfaces of tree trunks or branches

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Examples of Green Algae (Chlorophytes)

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Volvox (Fig 28.30a)
• Microscopic colonial green algae
• Each colony is motile
• Within some of the mature colonies you may find daughter colonies which separate to form new mature colonies

Chlamydomonas
• Unicellular green algae
• Chlamydomonas nivalis can form dense algal blooms on high altitude snowfields and glaciers where its reddish carotenoid pigments produce a visual effect known as “watermelon snow”

Ulva lactuca (sea lettuce)
• large green marine algae found along pacific coast
• sheet-like growth habit & is often found on rocks exposed at low tide
• a holdfast anchors it to the substrate
• Ulva life cycle demonstrates isomorphic alternation of generations with a haploid gametophyte and diploid sporophyte phase that
look similar

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Isomorphic Alternation of Generations

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the two (haploid & diploid) multicellular generations look similar morphologically
• example is Ulva (green algae)