Protista is one kingdom in the domain Eukarya.

Classification of Protists Protists are grouped by how they move and how they obtain nutrients. They are arranged into three main categories: animal-like protists, plant-like protists, and fungus-like protists. The animal-like protists are also known as protozoans, which is Latin for ‘first animals.

Plant-like protists are called algae (singular, alga). They are a large and diverse group. Some algae, diatoms, are single-celled….Classification of Algae.

Why is “Kingdom Protista” no longer a valid taxonomic grouping? Protists include all eukaryotes except the clades Planta, Animalia and Fungi. Since all of these organisms are presumed to share a common ancestor, protists as a group would not include all of its descendents thereby making the grouping paraphyletic.

The Protista, or Protoctista, are a kingdom of simple eukaryotic organisms, usually composed of a single cell or a colony of similar cells. Protists live in water, in moist terrestrial habitats, and as parasites and other symbionts in the bodies of multicellular eukaroytes.

Protists are found in many habitats, particularly those containing water.

• Basics. Protists are among the most complex living cells.
• Aquatic Environments. Protists make their homes in aquatic environments such as oceans, ponds, lakes and streams.
• Symbiotic Relationships.
• Jobs Within the Habitat.

In the five-kingdom system of Lynn Margulis, the term protist is reserved for microscopic organisms, while the more inclusive kingdom Protoctista (or protoctists) included certain large multicellular eukaryotes, such as kelp, red algae and slime molds.

Lesson Summary

• Animal-like protists are called protozoa. Most consist of a single cell.
• Plant-like protists are called algae. They include single-celled diatoms and multicellular seaweed.
• Fungus-like protists are molds. They are absorptive feeders, found on decaying organic matter.

Most protists are aquatic organisms. They need a moist environment to survive and are found in places where there is enough water for them, such as marshes, puddles, damp soil, lakes, and the ocean. Some protists are free-living organisms and others are symbionts, living inside or on other organisms, including humans.

Protists get food in one of three ways. They may ingest, absorb, or make their own organic molecules. Ingestive protists ingest, or engulf, bacteria and other small particles. They extend their cell wall and cell membrane around the food item, forming a food vacuole.