Protoctista
252
Protoctista one of the five kingdoms of organisms, which include all unicellular
eukaryotic living beings (except the unicellular Fungi like yeast) together with
the multicellular eukaryotic algae. All protoctists are composites, evolved
from more than a single type of microbial symbiont. At the moment more
than 100000 species have been described. The size range is enormous, the
smallest species being 1 ilm, the largest (giant kelps) to over 50 m length. For
the unicellular species within this kingdom still often the term Protista is
used. The term Protozoa is also still in use to denote the animal-like (motile
heterotrophic) unicellular species.
protoplast ~spheroplast.
Proto-Tethys ~Rheic Ocean.
Protozoa (protozoans) general term for a wide variety of microscopic unicellular
organisms (ca. 50000 species), most of which are motile and heterotrophic.
Protozoa live in the sea, in freshwater, or as parasites inside other organisms.
They usually multiply by fission (division of the cell into two or more new cells),
though sexual reproduction exists as well. The Protozoa were considered to
form one large group within the animal kingdom, though some are autotrophic
and contain chlorophyll and other pigments, which made it very difficult to decide
whether they are animals or plants (algae). At present, the different groups of
Protozoa are treated as separate phyla, which belong together with the algal
phyla to the kingdom Protoctista. Formerly Protozoa are split up into four different phyla, distinguished according to the types of locomotory organelles (specialized parts of the cell functioning as an organ in multicellular organisms):(l)
Sarcomastigophora, with locomotion by flagella or pseudopodia, divided into the
subphylum Mastigophora or Flagellata with the groups Euglenida, Volvocida, the
Dinophyceae or Dinoflagellata, and some other groups, and the subphylum
Sarcodina (locomotion by pseudopodia), divided into Amoebida, Foraminifera, Heliozoa,
Rhizomastigina and Radiolaria; (2) and (3) Apicomplexa and Microspora, resp.,
together known as the Sporozoa, parasitic protozoans living within or between
the cells of the animal host; (4) Ciliophora, ciliates, the largest phylum of the
Protozoa (more than 7000 species), which move and take their food with cilia.
proximal situated near point of attachment; opposite of distal.
Prymnesiophyta (syn. Haptophyta), coccolithophorids and relatives. A phylum within
the kingdom Protoctista. These nanoplanktonic algae have a special filament,
the haptonema, besides their flagella. They contain chlorophyll-c and 19'hexanoylfucoxanthin and some carbohydrate as fluid chrysolaminarin, or as
paramylon. The haptonema may be long and coilable, but more often it is
much reduced. Coccoliths are organic scales covered by small calcite crystals.
Cricosphaera is a coastal coccolitophorid. Most coccolithophorids are
252
Protoctista one of the five kingdoms of organisms, which include all unicellular
eukaryotic living beings (except the unicellular Fungi like yeast) together with
the multicellular eukaryotic algae. All protoctists are composites, evolved
from more than a single type of microbial symbiont. At the moment more
than 100000 species have been described. The size range is enormous, the
smallest species being 1 ilm, the largest (giant kelps) to over 50 m length. For
the unicellular species within this kingdom still often the term Protista is
used. The term Protozoa is also still in use to denote the animal-like (motile
heterotrophic) unicellular species.
protoplast ~spheroplast.
Proto-Tethys ~Rheic Ocean.
Protozoa (protozoans) general term for a wide variety of microscopic unicellular
organisms (ca. 50000 species), most of which are motile and heterotrophic.
Protozoa live in the sea, in freshwater, or as parasites inside other organisms.
They usually multiply by fission (division of the cell into two or more new cells),
though sexual reproduction exists as well. The Protozoa were considered to
form one large group within the animal kingdom, though some are autotrophic
and contain chlorophyll and other pigments, which made it very difficult to decide
whether they are animals or plants (algae). At present, the different groups of
Protozoa are treated as separate phyla, which belong together with the algal
phyla to the kingdom Protoctista. Formerly Protozoa are split up into four different phyla, distinguished according to the types of locomotory organelles (specialized parts of the cell functioning as an organ in multicellular organisms):(l)
Sarcomastigophora, with locomotion by flagella or pseudopodia, divided into the
subphylum Mastigophora or Flagellata with the groups Euglenida, Volvocida, the
Dinophyceae or Dinoflagellata, and some other groups, and the subphylum
Sarcodina (locomotion by pseudopodia), divided into Amoebida, Foraminifera, Heliozoa,
Rhizomastigina and Radiolaria; (2) and (3) Apicomplexa and Microspora, resp.,
together known as the Sporozoa, parasitic protozoans living within or between
the cells of the animal host; (4) Ciliophora, ciliates, the largest phylum of the
Protozoa (more than 7000 species), which move and take their food with cilia.
proximal situated near point of attachment; opposite of distal.
Prymnesiophyta (syn. Haptophyta), coccolithophorids and relatives. A phylum within
the kingdom Protoctista. These nanoplanktonic algae have a special filament,
the haptonema, besides their flagella. They contain chlorophyll-c and 19'hexanoylfucoxanthin and some carbohydrate as fluid chrysolaminarin, or as
paramylon. The haptonema may be long and coilable, but more often it is
much reduced. Coccoliths are organic scales covered by small calcite crystals.
Cricosphaera is a coastal coccolitophorid. Most coccolithophorids are