Chromista

Chromista is a proposed kingdom of eukaryotes that includes organisms such as diatoms, brown algae, and oomycetes. Its membership varies among classifications.

Eukaryote: An organism whose cells contain a nucleus and membrane-bound organelles. Chromista is proposed as one kingdom within the eukaryotes.
Diatom: A single-celled alga whose cell wall contains intricately patterned silica. Diatoms are a major photosynthetic group commonly assigned to Chromista.
Thomas Cavalier-Smith: A British biologist known for influential proposals about eukaryotic classification and evolution. He proposed Chromista as a kingdom in a system that grouped diverse lineages.
SAR supergroup: A major eukaryotic grouping comprising stramenopiles, alveolates, and rhizarians. SAR organizes many proposed chromists with rhizarians, which are often excluded from Chromista.
Stramenopile: A major eukaryotic lineage that includes diatoms, brown algae, and oomycetes. Many organisms assigned to Chromista belong to this lineage.
Brown algae: A group of mostly marine multicellular algae that includes kelps. Brown algae are conspicuous chromists and include the largest seaweeds.
Endosymbiotic theory: The theory that some eukaryotic organelles originated as free-living bacteria engulfed by ancestral cells. Complex plastid histories helped shape hypotheses about chromist relationships.
Protist: An informal term for eukaryotes that are not animals, plants, or fungi. Protist is broader and less formal than kingdom-level Chromista.
Alveolate: A eukaryotic lineage characterized by membrane-bound sacs beneath the cell surface. Some classifications place alveolates alongside stramenopiles within Chromista.
Oomycete: A group of fungus-like organisms that includes many water molds and plant pathogens. Oomycetes show that proposed Chromista includes nonphotosynthetic members.

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ProtozoaRelated: Some organisms once called protozoa are classified among chromists in modern schemes.