"Protists"
SAR Supergroup
The term protist is an old "catch-all" term for algal-like or fungal-like organisms that didn't seem to fit into other kingdoms. With better technology, the evolutionary relationships of these organisms are being refined. The "protists" that are presented all exist in the SAR supergroup, which is an acronym for the Stramenopiles, the Alveolates, and Rhizaria. They descended from an endosymbiotic event between a bikont (organism with 2 flagella) and a red alga, which became the ancestor of chloroplastid with chlorophyll c. Thus, the photosynthetic members of this group possess both chlorophyll a and c
Classification
SAR Supergroup (Stramenopiles, Alveolata, Rhizaria)
Infrakingdom Heterokontophyta (or also called Stramenopiles)
Water molds (Oomycota)
Diatoms (Bacillariophyceae)
Brown algae (Phaeophyceae)
Infrakingdom Alveolata
Dinoflagellates (Dinoflagellata)
Infrakingdom Rhizaria (not covered in this website)
Questions for Thought
Why is the term "protist" not very useful for evolutionary studies?
What is the synapomorphy of the Chromalveolates? ... of the Heterokonts? ...of the Alveolates?
What life cycle (i.e. haplontic, diplontic, diplo-haplontic) does each group exhibit?
The brown algae are not closely related to land plants, but what aspect of their life cycle made past researchers assume an ancestor-descendant relationship?
How have the water molds impacted plants and human history?
Why are the diatoms so ecologically significant?
Why are dinoflagellates so ecologically significant?
What ecological niche(s) do the brown algae occupy?
Additional Resources
Marine Algae Gene Unlocks Potential For Super Crops (Science Blog 6Mar2024)
Climate change clues from tiny marine algae - ancient and modern