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Biology 2014-2015

Unicellular Algae

SWS Biology
SWS Life Science


Freshwater Diatoms


Saltwater Diatoms



    plantlike protists are commonly called "algae"

    contain the green pigment chlorophyll and carry out photosynthesis

    highly motile or are able to move about freely


Chlorophyll and Accessory Pigments

    classified by the type of photosynthetic pigments they contain

    a shortage of light is a major problem for deep water algae

    sea water absorbs large amounts of red and violet light

    chlorophyll a is the best at capturing red and violet light

    forms of chlorophyll include:

       chlorophyll a

       chlorophyll b

       chlorophyll c

    accessory pigments are compounds that absorb light at different wavelengths than chlorophyll

       give algae a wide range of colors



    phylum Chrysophyta includes the yellow-green algae and the golden-brown algae.

    contain bright yellow pigments

    means "golden plants"

    cell walls contain pectin rather than cellulose

    store food in the form of oil rather than starch

    reproduce both asexually and sexually; most are solitary



    phylum Bacillariophyta or diatoms are most abundant and beautiful organisms on Earth

    cell walls are rich in  silicon (main component of glass)

    form diatomaceous earth used in polishing metals or insulation/filtration

                        Two groups:  Centric - circular, common in oceans

                                               Pennate - rectangular, common in fresh                                                                       water ponds and lakes



    phylum Pyrrophyta are dinoflagellates

    half are photosynthetic and half are heterotrophic

    2 flagella that wrap around the organism in cellulose grooves that protect the cell

    luminescent and when agitated by sudden movement give off light, hence the name "fire plants"


Ecology of Unicellular Algae

    common in both fresh and salt water

    make up a considerable part of the phytoplankton

    phytoplankton are small, photosynthetic organisms found near the surface of the ocean.

    half of the photosynthesis is carried out by phytoplankton

    nourishment for shrimp and whales


Algal Blooms

    many protists grow rapidly in regions where sewage is discharged

    when waste is excessive, algae may grow in enormous masses known as blooms

    blooms deplete the water of nutrients, and cells die in great numbers

    decomposition of dead algae robs water of oxygen, choking resident fish and invertebrates

       great blooms of the dinoflagellates Gonyaulax and Karenia have recently occurred on the east coast of the US.

       known as "red tide"

       produce a potentially dangerous toxin







       filter-feeding shellfish such as clams eat the algae and become filled with the toxin humans and fish can become seriously ill, paralyzed or even die from eating shellfish infected with red tide