The kingdom Heterkonta (also known as Straminopiles or Chromalveolata) is characterised by the fact that the (unicellular) motile stages possess two flagella that are strongly different in shape and function. One is a simple whip flagellum that also is found in primitive fungi. The other is a dragging flagellum with complex structure, somewhat resembling a test tube brush. This second type is unique to the Heterkonta.

Most groups have photosynthic pigments and are autotrophic, like Bacillariophyceae (diatoms), Chrysophyceae (gold algae), Phaeophyceae (brown algae), Xanthophyceae (yellow-green algae); others lack pigments and are saprophytes or parasites, like the Oomycota (“water moulds”)

mod 25.vii.2017