Protist

A eukaryotic organism outside the groups of animals, plants, and fungi. Protists span diverse evolutionary lineages rather than forming one natural group.

Eukaryote: An organism whose cells contain a nucleus and membrane-bound organelles. Protists are eukaryotes, distinguished from bacteria and archaea by their cellular organization.
Cilia: Short, hairlike cell projections that move cells or propel material across their surfaces. Cilia let ciliates swim and sweep food particles toward their cell mouths.
Amoeba: A single-celled eukaryote that moves and feeds by extending temporary portions of its cell membrane. Amoebae exemplify flexible cell shape and movement among protists.
Malaria: A mosquito-borne disease caused by Plasmodium parasites. Malaria is the major human disease caused by a protist.
Animal: A multicellular eukaryote that obtains nutrients by consuming other organisms or organic matter. Animals are excluded from the traditional protist category despite sharing eukaryotic cells.
Endosymbiotic theory: The theory that mitochondria and chloroplasts originated as bacteria living inside ancestral cells. Endosymbiosis explains the origins of organelles found in many protists.
Flagellum: A whip-like cellular appendage that drives movement in many eukaryotic cells. Many flagellated protists use one or more flagella to move through water.
Paramecium: A ciliate protist with an elongated cell covered in rows of beating cilia. Paramecium illustrates how cilia can support both locomotion and feeding.
Trypanosomiasis: A group of diseases caused by Trypanosoma parasites and transmitted by insect vectors. Trypanosomes are protists whose infections include African sleeping sickness and Chagas disease.
Plant: A member of the land-plant lineage, typically multicellular and photosynthetic. Plants are excluded from protists, though some protists also photosynthesize.

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