Download BLUE-GREEN ALGAE · CYANOBACTERIA

CYANOBACTERIA, DINOPHYTA,
BACILLARIOPHYCEAE, &
COSCINODISCOPHYCEAE
Objective
Today we will examine members of the Cyanobacteria, Dinophyta, Bacillariophyceae,
Coscionodiscophyceae and Magnoliophyta. We will become familiar with aspects of their diversity,
variation in morphology, and special thallus features.
Notebook Requirements: 12 drawings
Phytoplankton (treasure hunt):
Drawings:
 Draw 3 Diatoms
 Draw 3 Dinoflagellates
 Note: For taxonomy, you only need to include Division, Class (diatoms) and Genus (make best
guess from drawings on lab handout provided)
Questions:
Define each term and suggest its function:
 Raphe
 Undulopodium
 Frustule
 Auxospore
 Girdle
 Planozygote
 Epicone
 Hypnozygote
 Hypocone
 Trichocysts
1. Label the ploidy of diatoms & dinoflagellates. What type of life history do each have?
2. Describe asexual reproduction in diatoms. What triggers sexual reproduction in diatoms?
3. What triggers asexual and sexual reproduction in dinoflagellates?
4. What types of strategies do diatoms and dinoflagellates use to stay in the photic zone?
Cyanophyta:
Drawings:
 Draw Spirulina (live)
 Draw Oscillatoria (live)
 Draw Anabaena and Nostoc (live)
o Label: heterocysts, akinetes
 Draw Tolypothrix (prepared slide)
o Label and define: false branching
 Draw Stigonema (prepared slide)
o Label and define: true branching
 Bonus: Look for and label hormogonia (notify TA if you find any)
Questions:
Define each term and suggest its function:
 Filament
 Trichome
 Sheath
 Heterocyst
 Hormogonia
 Akinete
 Gas vacuoles
 Carboxysome
1. Under what conditions are heterocysts and akinetes formed?
2. Describe the process of nitrogen fixation. Why does it need to occur in a specia lized
environment? Name the enzyme involved.
3. Besides heterocyst formation, what other ways can some Cyanophyta spatially separate the
enzyme used to fix atmospheric nitrogen from oxygen?
4. Describe the fate of an akinete once it is formed within the trichome. Are akinetes positively
or negatively buoyant?
Introduction - Cyanobacteria
Although the exact number of species is debatable, “Algaebase.org” estimates there to be about
~4000 species. Being Bacteria, the Cyanobacteria lack membrane bound organelles. However,
given that they have chlorophyll a and release oxygen through photosystems I & II, we will
consider them to be “algae.” The Cyanobacteria (also called bluegreen algae) are the oldest
organisms to give off oxygen via Photosystems I and II and are estimated to have existed for
between 2.2 and 3.5 billion years; fossil stromatolites (layered rocks formed by accretion of
minerals around cells) date back to the Precambrian period.
The Cyanobacteria are ubiquitous, occurring in both seawater and freshwater, on unconsolidated
substrata—endolithically in deserts and in Antarctic ice, and epilithically on tropical intertidal
limestone. They are important fixers of nitrogen, contibute to toxic red tides, and were some of
the first organisms to give off oxygen, thus playing a pivotal role in creating Earth’s oxidizing
atmosphere. Many species possess specialized thick-walled cells called heterocysts that aid in
nitrogen fixation by separating the site of nitrogen fixation from sources of oxygen.
Systematics - CYANOPHYTA
Orde r
Thallus
Characteristics
Examples
Chroococcales Unbranched filaments
fragmentation, hormogonia production,
no specialized cells
Spirulina
Oscillatoriales
Unbranched filaments
fragmentation, hormogonia production,
no specialized cells
Oscillatoria,
Nostocales
Unbranched filaments
Branched filaments
May have heterocysts, hormogonia and
akinetes
Nostoc,
Anabaena,
Tolypothrix
Stigonema
LIVE SPECIMENS - CYANOPHYTA
Spirulina
Anabaena
Filamentous, common in lakes with high soda, high pH, spiraled trichomes.
Planktonic, anatoxin (neurotoxin) hepatoxin, heterocysts visable, negative phototaxis—
can steer the tip of the filament towards light.
Nostoc
Often associated with fungi in lichens, filamentous, can form colonies, akinetes
midway between heterocysts.
PREPARED SPECIMENS - CYANOPHYTA
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Tolypothrix
Stigonema
Planktonic, often in freshwater lakes, false branching at heterocysts
Inhabits moist rocks and soil, often associated with fungi in lichens,
filaments can be multiple cells in width (multiseriate), exhibits true
branching
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