BSC 310 Lecture Notes - Lecture 30: Phototroph, Zygote, Gametocyte
Divisions of Unicellular Algae
Five divisions of unicellular algae are considered in microbiology because of their
microscopic form and their unicellular characteristic. These organisms are classified in
the kingdom Protista.
Division Chlorophyta.Algae of the division Chlorophytapossess green chlorophyll
pigments and carotenoid pigments. A representative member is Chlamydomonas, which
is often used in research and as a laboratory
specimen. Chlamydomonas produces zoospores, which are flagellated. Organisms
such as Chlamydomonas are believed to be evolutionary ancestors of other species.
Other organisms in the division are Volvoxand Spirogyra.
Division Charophyta. Members of the
division Charophyta are stoneworts. Stoneworts cover the bottoms of ponds and may
be a source of limestone.
Division Euglenophyta. Members of the division Euglenophyta include the common
organism Euglena. These organisms have chlorophyll and carotenoid pigments for
photosynthesis and flagella for movement. They share many characteristics with both
plants and animals and are believed to be a basic stock of evolution.
A typical Euglena cell has a large nucleus and nucleolus. Contractile vacuoles help
empty water from the organism, and two flagella arise at one end of the cell.
Reproduction occurs by binary fission in the longitudinal plane.
Division Chrysophyta. Members of the division Chrysophyta are brown and yellow‐
green algae. These organisms contain chlorophyll pigments as well as special
carotenoid pigments called fucoxanthins. Fucoxanthins give the golden brown color to ‐
members of the division. Members of the division include the diatoms, oceanic
photosynthetic algae found at the bases of many food chains. Diatoms contribute
immense amounts of oxygen to the atmosphere and occupy key places in the spectrum
of living things because they convert the sun's energy into the energy in carbohydrates.
Division Pyrrophyta. Members of the division Pyrrophyta are pigmented marine forms
that include the dinoflagellates, amoeboid cells with flagella as well as protective
cellulose plates that surround the cells. They have chlorophyll, carotenoid, and
xanthophyll pigments. Dinoflagellates often have a brown or yellow color, and they
reproduce by longitudinal division through mitosis. Dinoflagellates make up a large
portion of marine plankton and are essential to many of the ocean food chains. Certain
species are luminescent. Others have red or orange pigments; when these organisms
multiply at abnormally high rates, they cause the “red tides.”
General Characteristics of Algae
Algae are eukaryotic organisms that have no roots, stems, or leaves but do have chlorophyll
and other pigments for carrying out photosynthesis. Algae can be multicellular or unicellular.
Unicellular algaeoccur most frequently in water, especially in plankton. Phytoplankton is the
population of free‐floating microorganisms composed primarily of unicellular algae. In
addition, algae may occur in moist soil or on the surface of moist rocks and wood. Algae live
with fungi in lichens.
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Document Summary
Five divisions of unicellular algae are considered in microbiology because of their microscopic form and their unicellular characteristic. These organisms are classified in the kingdom protista. Division chlorophyta. algae of the division chlorophytapossess green chlorophyll pigments and carotenoid pigments. A representative member is chlamydomonas, which is often used in research and as a laboratory specimen. Organisms such as chlamydomonas are believed to be evolutionary ancestors of other species. Other organisms in the division are volvoxand spirogyra. Stoneworts cover the bottoms of ponds and may be a source of limestone. Members of the division euglenophyta include the common organism euglena. These organisms have chlorophyll and carotenoid pigments for photosynthesis and flagella for movement. They share many characteristics with both plants and animals and are believed to be a basic stock of evolution. A typical euglena cell has a large nucleus and nucleolus. Contractile vacuoles help empty water from the organism, and two flagella arise at one end of the cell.
