protistes

Protists, often referred to as protistes in some languages, are a diverse group of mostly single‑celled eukaryotes that do not belong to the plant, animal, or fungal kingdoms. Historically placed in a single kingdom named Protista, modern systematics treat Protista as a loose, non‑monophyletic category that groups together many distinct lineages within the domain Eukarya. In practice, “protist” is a useful umbrella term for eukaryotes that are not easily classified as other major kingdoms.

The diversity of protists is vast. They include photosynthetic algae such as diatoms, dinoflagellates, and green algae, as well as non‑photosynthetic groups such as protozoa (for example, amoebae, ciliates, and flagellates). Slime molds and some other simple multicellular forms are also included in traditional discussions of protists. Protists can be unicellular, colonial, or, in some lineages, truly multicellular.

Cell biology among protists is equally varied. They range from simple, free‑living cells to highly organized organisms with complex life cycles and diverse reproductive strategies, including asexual division, sexual reproduction, and spore formation. Many protists possess organelles such as mitochondria and, in photosynthetic lineages, chloroplasts acquired through endosymbiosis.

Ecologically, protists inhabit virtually every moist environment, including oceans, rivers, soils, and wetlands. They play critical roles as primary producers, decomposers, and as part of the food web, and some are parasites or pathogens. Their study contributes to understanding eukaryotic evolution, ecology, and the biology of microscopic life.