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.
- 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?