Animal-like Protists
Jessica Harwood
Douglas Wilkin, Ph.D.
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AUTHORS
Jessica Harwood
Douglas Wilkin, Ph.D.
EDITOR
Douglas Wilkin, Ph.D.
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Printed: November 9, 2015
CONTRIBUTORS
Doris Kraus, Ph.D.
Niamh Gray-Wilson
Jean Brainard, Ph.D.
Sarah Johnson
Jane Willan
Corliss Karasov
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C HAPTER
Chapter 1. Animal-like Protists
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Animal-like Protists
• Define protozoa.
• Describe the types of animal-like protists.
• Distinguish flagellates from ciliates.
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
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.
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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 1.1). 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.
FIGURE 1.1
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 .
Summary
• 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.
Explore More
Use the resource below to answer the questions that follow.
• What are Protozoa? - Definition, Characteristics Examples at http://education-portal.com/academy/less
on/what-are-protozoa-definition-characteristics-examples.html#lesson
1. Who proposed the five kingdom taxonomic system?
2. How did the Kingdom Protista come about?
3. Define protozoa.
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Chapter 1. Animal-like Protists
4. There are four groups of protozoa. What are the four groups and how are these groups distinguished?
5. What is a flagellate?
6. What distinguishes the sporozoans?
Review
1. What features describe the protozoa?
2. What are three main types of protozoa?
3. Distinguish flagellates from ciliates.
References
1. Laura Guerin. These flagellates all cause diseases in humans . CC BY-NC 3.0
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