Which kingdom includes simple, mostly single-celled eukaryotes not classified as plants, animals, or fungi?

Which kingdom includes simple, mostly single-celled eukaryotes not classified as plants, animals, or fungi?

• A. Plantae
• B. Protista
• C. Animalia
• D. Fungi

Answer: (B)

Recognizing organisms that are eukaryotic, often simple and single-celled, but not part of the plant, animal, or fungal lineages. This is why the group Protista fits: it historically served as a catch-all kingdom for diverse eukaryotes that don’t share the defining features of plants (multicellular, photosynthetic, cellulose walls), animals (multicellular, ingestive heterotrophs), or fungi (mostly multicellular, absorptive, with chitin walls). Protists can be unicellular or simple colonies and include a range of modes of life, from photosynthetic algae to slime molds and protozoa that ingest nutrients. The other kingdoms describe more tightly linked traits—plants being predominantly photosynthetic, multicellular organisms with cell walls; animals being multicellular and heterotrophic without cell walls; fungi being mostly multicellular absorbers with chitin walls. Because the question targets those simple, mostly single-celled eukaryotes that don’t fit the other groups, Protista is the best match.

Recognizing organisms that are eukaryotic, often simple and single-celled, but not part of the plant, animal, or fungal lineages. This is why the group Protista fits: it historically served as a catch-all kingdom for diverse eukaryotes that don’t share the defining features of plants (multicellular, photosynthetic, cellulose walls), animals (multicellular, ingestive heterotrophs), or fungi (mostly multicellular, absorptive, with chitin walls). Protists can be unicellular or simple colonies and include a range of modes of life, from photosynthetic algae to slime molds and protozoa that ingest nutrients. The other kingdoms describe more tightly linked traits—plants being predominantly photosynthetic, multicellular organisms with cell walls; animals being multicellular and heterotrophic without cell walls; fungi being mostly multicellular absorbers with chitin walls. Because the question targets those simple, mostly single-celled eukaryotes that don’t fit the other groups, Protista is the best match.