What can hunt prey and move, but is not an animal?
Some protists, like these Paramecium , act much like animals. Notice the tiny hair-like cilia that help them move. The food vacuoles, where they digest their prey, are colored in orange.
Animal-like protists are called protozoa. Protozoa are single-celled eukaryotes that share some traits with animals. Like animals, they can move, and they are heterotrophs . That means they eat things outside of themselves instead of producing their own food.
Animal-like protists are very small, measuring only about 0.01–0.5mm. Animal-like protists include the flagellates, ciliates, and the sporozoans.
Different Kinds of Animal-like Protists
There are many different types of animal-like protists. They are different because they move in different ways.
- Flagellates have long flagella, or tails. Flagella rotate in a propeller-like fashion, pushing the protist through its environment ( Figure below ). An example of a flagellate is Trypanosoma , which causes African sleeping sickness.
- Other protists have what are called transient pseudopodia , which are like temporary feet. The cell surface extends out to form feet-like structures that propel the cell forward. An example of a protist with pseudopodia is the amoeba.
- The ciliates are protists that move by using cilia. Cilia are thin, very small tail-like projections that extend outward from the cell body. Cilia beat back and forth, moving the protist along. Paramecium has cilia that propel it.
- The sporozoans are protists that produce spores, such as the toxoplasma . These protists do not move at all. The spores develop into new protists.
These flagellates all cause diseases in humans.
A video of the animal-like amoeba can be viewed at: http://commons.wikimedia.org/wiki/File:Amoeba_engulfing_diatom.ogg .
- cilia : Very small tail-like projections that beat back and forth to allow movement.
- ciliate : Type of protozoa, such as Paramecium , that moves with cilia.
- flagellate : Type of protozoa, such as Giardia , that moves with flagella.
- heterotroph : Organism that must eat food to obtain energy.
- protozoa : Single-celled eukaryotes that share many traits with animals.
- pseudopodia : Temporary feet where the cell surface extends out.
- sporozoa ( singular , sporozoan ): Type of protozoa that cannot move as adults.
- Protozoa are single-celled eukaryotes that share some traits with animals.
- Protozoa can move by flagella, cilia, or pseudopodia, or they may not move at all.
Use the resource below to answer the questions that follow.
- Protozoa Classification Part 1 at http://www.youtube.com/watch?v=KQBE94x5TfE (8:19)
- What are the characteristics of Sarcomastigophora? Where can they be found?
- What are the characteristics of Sporozoa? Where can they be found?
- What are the characteristics of Cnidospora? Where can they be found?
- What are the characteristics of Ciliophora? Where can they be found?
- What features describe the protozoa?
- How can animal-like protists move?