Protist is a catch-all term that usually refers to single-celled, eukaryotic organisms. Protists can be animal-like, fungal-like or plant-like in terms of the organelles they contain. The animal-like protists have traditionally been called “protozoans.” They are heterotrophic and usually have structures for motility. Plant-like protists are autotrophic and capable of photosynthesis. Many of them are floaters, with no structures for motility.
Protists are among the largest of all eukaryotic cells. They often have specialized organelles that are not found in the cells of multicellular organisms. These organelles combine to accomplish the basic functions that we associate with entire organ systems of plants and animals. For example, there are organelles in some freshwater protists that maintain osmotic equilibrium by pumping excess fluid out of the cell—a function performed by the urinary system of most animals. There are also protists that do not fit neatly into plant-like or animal-like categories.
- Study the following video of an ambiguous protist. (The video has no sound.) Then write a short description indicating why you think the protist is more animal-like or more plant-like. (Base your answer on observations of the protist.)
Ambiguous Protist. Introductory Biology: Ecology, Evolution, and Biodiversity. Retrieved March 27, 2018, from http://projects.ncsu.edu/project/bio181de/Lab/protists-fungi/euglena.html
- View the following video of two animal-like protists, Stentor and Voticella (audio included), and then answer the questions listed below:
Stentor and Vorticella. Introductory Biology: Ecology, Evolution, and Biodiversity.Retrieved March 27, 2018, from http://projects.ncsu.edu/project/bio181de/Lab/protists-fungi/protozoans.html
- Describe the ways in which Stentor and Vorticella feed; what structures are involved in feeding?
- Name, and briefly describe, one internal organelle in each protist.
- Research one additional protist. Insert an image of your chosen protist into your word document (it should be no larger than 2.5-by-3 inches). Describe its beneficial or harmful effects on humans.