Section 18
Protists
By Boundless
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Protists are eukaryotes that first appeared approximately 2 billion years ago with the rise of atmospheric oxygen levels.
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Excavata, defined by a feeding groove that is "excavated" from one side, includes Diplomonads, Parabasalids and Euglenozoans.
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Alveolates are defined by the presence of an alveolus beneath the cell membrane and include dinoflagellates, apicomplexans and ciliates.
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Stramenophiles include photosynthetic marine algae and heterotrophic protists such as diatoms, brown and golden algae, and oomycetes.
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Rhizaria are a supergroup of protists, typically amoebas, that are characterized by the presence of needle-like pseudopodia.
![Thumbnail](../../../../../../figures.boundless-cdn.com/19153/square/figure-23-03-17.jpeg)
Amoebozoa are a type of protist that is characterized by the presence of pseudopodia which they use for locomotion and feeding.