…And the 3 “Classic” Protists! The Protist Kingdom …And the 3 “Classic” Protists!

What is a Protist? Protists: Eukaryotic organisms that cannot be classified as animals, plants, or fungi. Protists are very varied, but they do have some similarities. Beside the fact that they are all eukaryotic, they all live in moist surroundings as well.

How Diverse? The protists kingdom is one of the most diverse. Most are unicellular, although some are multicellular. Some are heterotrophs, some are autotrophs and some are…. BOTH! Some protists cannot move while some others have no problem zipping around their surroundings.

How are they grouped? Because protists are so varied, Scientist group them into smaller categories: Animal-like protists (protozoa) Plantlike protists (algae) Funguslike protists (funguslike) Though we will be discussing all protists in class, this powerpoint will focus on the animal-like protists.

Animal-like Protists Like animals, animal-like protists are heterotrophs. Most are able to move from place to place to obtain food. Unlike animals, animal-like protists are unicellular. Animal-like protists are also called Protozoans.

Protozoans Just as protists are split into smaller groups, so are protozoans. They can be split into 4 categories based on the way they move and get food. The groups are: Protozoans with pseudopods (sarcodines) Protozoans with cilia (ciliates) Protozoans with flagella (flagellates) Protozoans that are parasites

Protozoans with Pseudopods Protozoans that have pseudopods are called sarcodines. Pseudopod: Means “false foot”, it is a temporary bulge of the cell that allows for feeding and movement. Pseudopods form when cytoplasm flows toward one location and the rest of the cell follows.

Amoeba Amoeba: Sarcodines that live in either water or soil. They feed on bacteria and smaller protists. Like all sarcodines, amoebas move and obtain food with their pseudopods.

Amoeba

Protozoans in fresh water Protozoans that live in fresh water have a big problem. Water can move easily through the cell membrane and too much can cause the cell to burst (passive transport or osmosis). Fortunately for these protozoans, they have a contractile vacuole. A contractile vacuole is a structure that collects and expels excess water from the cell.

Protozoans with Cilia Protozoans with cilia are called ciliates. Cilia: Hair like projections from a cell that move with a wavelike motion. Just like pseudopods, ciliates use cilia to move and obtain food. Ciliates have complex cells. Many have more than one contractile vacuole and some (like paramecium), have 2 nuclei. The macronucleus (large) controls everyday tasks and the micronucleus (small) aids in reproduction.

Paramecium Paramecium: Ciliates that live mostly in fresh water. Like amoebas, paramecia feed on bacteria and smaller protists. Like all ciliates, paramecia move and obtain food with their cilia.

Paramecium

Protozoans with flagella Protists with flagella are called flagellates. Flagella: Whip-like structure that allows for movement. Many flagellates form symbiotic relationships, both good and bad.

Euglena Euglena: A common protozoa that lives in fresh water. In sunlight, euglena can make their own food. What makes them bizarre is that when the lights go down, they become heterotrophic predators! Like all flagellates, euglena move with a flagellum.

Euglena

Parasitic Protozoans Protozoans that are parasitic feed on cells and bodily fluids of their hosts. They move in a variety of ways, some have flagella and some depend on their host for movement. Some have more than one host, relying on one organism for transport and one for food.