Chromista is a proposed but polyphyletic biological kingdom, refined from the Chromalveolata, consisting of single-celled and multicellular eukaryotic species that share similar features in their photosynthetic organelles (plastids). It includes all eukaryotes whose plastids contain chlorophyll c and are surrounded by four membranes. If the ancestor already possessed chloroplasts derived by endosymbiosis from red algae, all non-photosynthetic Chromista have secondarily lost the ability to photosynthesise. Its members might have arisen independently as separate evolutionary groups from the last eukaryotic common ancestor.
Chromista
Structure of some types of Chromista compared with plant cell (left). The idea was that the Chromista had arisen, supposedly just once (making them monophyletic, and in Tom Cavalier-Smith's view a separate Kingdom) by enslaving a red alga, ending up with multiple membranes around what became their red plastids. Groups lacking red plastids were supposed to have secondarily lost them. The Cryptophyta are within the Cryptista; the Myzozoa are within the
Chromista classification according to Cavalier-Smith, 2018, with supposed events marking group divergences
Chromalveolata was a eukaryote supergroup present in a major classification of 2005, then regarded as one of the six major groups within the eukaryotes. It was a refinement of the kingdom Chromista, first proposed by Thomas Cavalier-Smith in 1981. Chromalveolata was proposed to represent the organisms descended from a single secondary endosymbiosis involving a red alga and a bikont. The plastids in these organisms are those that contain chlorophyll c.
Chromalveolata
A Californian kelp forest
A potato plant infected with Phytophthora infestans
