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Natural Perspective

The Protoctist Kingdom (Protoctistae)

(Last modified: 4 May 2015)
The Protoctista Kingdom is a catch-all for the multicellular organism which don't fit into the Animal, Plant, or Fungus Kingdom.

Depending on how you split things, this Kingdom contains from 20 to 50 distinct Phyla. Dr. Margulis counts 27 in the 1988 edition of Five Kingdoms: An Illustrated Guide to the Pyla of Life on Earth but alludes to the higher number in a paper she coauthored.

With the exception of the larger Algae -- seaweeds and kelp -- Protoctista are pretty much all microscopic organisms.

Green Algae (Gamophyta & Chlorophyta)

7000 species

Red Algae (Rhodophyta)

4000 species such as this Coralline Alga (Calliarthron tuberculosum)

Brown Algae (Phaeophyta)

1500 species such as this Feather Boa Kelp (Egregia menziesii) which can grow up to 25 feet (8 meters) long.

Other species include Diatoms (Bacillariophyta, 10,000 species) and various Plankton

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Credits:

Collaboration and inspiration thanks to Susan Kornfeld

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Special thanks to Claire Doyle Ragin for scanning some early photos

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