University of Pittsburgh at Bradford
Science in Motion
Biology 012
Protist Identification
Introduction:
The kingdom Protista contains diverse species that share several characteristics. A protist is a
eukaryotic, meaning that their DNA is enclosed in a nucleus inside the cell, unlike bacteria that
are prokaryotic and have no nucleus to surround their DNA. It lacks complex organ systems and
lives in moist environments. There are several types of protists. Fossils of plant-like protists,
which contain chlorophyll and are able to produce their own food, show that protists existed on
Earth up to two billion years ago. An alga is a plant-like protist. Varieties include euglenas,
diatoms, dinoflagellates, green algae, red algae and brown algae. Algae are important as primary
producers of organic matter at the base of the food chain. They also provide oxygen for other
aquatic life. Algae may contribute to mass mortality of other organisms, in cases of algal blooms,
but they also contribute to economic well- being in the form of food, medicine and other
products. In tropical regions, coralline algae can be as important as corals in the formation of
reefs.
Protozoa are animal-like such that they are unable to make their own food and depend on hunting
and gathering to eat. Varieties of protozoa include sarcodines, flagellates, ciliates and
sporozoans. Some protozoan can cause disease. Mosquitoes spread the protozoan that causes
Malaria. The word protozoa means "any of the singled-cell, usually microscopic organisms of
the phylum or subkingdom Protozoa, which includes the most primitive forms of animal life."
Protozoan comes from the New Latin word Protozoa which was formed by the word proto,
which means first, and zoan which means animal.
Slime molds are the third group of protists. These protists are parasites or decomposers. These
organisms can cause disease that can destroy food crops. Fungus-like protists also cause disease
in animals. Although some protists are unicellular, others are multicellular.
The method of locomotion is one of the factors used to identify the protists. Cilia are short, hairlike structures, flagella are long, whip-like structures, and pseudopods are cytoplasm-containing
extensions of the protist’s plasma membrane.
Classifying organisms can be a useful tool for scientists who work in agriculture, forestry, and
medicine. One such instrument that is used to help with classifying is called a dichotomous key.
This key is made up of sets of numbered statements. Each set deals with a single characteristic
of an organism, such as color. Follow the numbered sets until they key reveals the name of the
organism.
The culture of protists that you will be working with contains nine different protist types that you
will be asked to identify using the dichotomous key provided.
Objectives:
1. Students will be able to utilize a dichotomous key to identify the protists by their
characteristics.
2. Students will be able to discuss the differences found in the protists available.
3. Students will be able to use the digital microscope in order to identify the organism and
will learn how to make microscopic measurements.
Materials:
Computer
Motic System/Digital Microscope
Lens Paper
Mixed Protist Culture
Micro Concave Slide
Dichotomous Key of Protists
Beral Pipet
Procedure:
1. To bring up the motic system: Double click on the Motic Images icon on the desktop.
2. File: Capture Window. This will enable you to view the images on your screen.
3. Prepare a slide of protist culture by placing two drops of the culture onto your concave
slide using a beral pipet.
4. Place 1-2 drops of detain into the well of the slide to slow organisms’ movements.
5. Place slide on microscope and bring into focus viewing the image on your laptop screen.
This should be at low power on the 4X objective lens. If your image is too DARK to
view: click on the Option: Video Capture filter: change the Brightness.
6. Increase the magnification of the protist until you are either at the 10x or 40x—depending
on the size of your organism. You must be able to view the entire organism in your
capture window.
7. Using the motic system you are able to measure your organism:
a. You must snap a photo of your organism: Capture: Still Image
b. Click on the LINE icon • • This will bring up a box at the bottom of the screen.
Select the correct objective lens that you are looking through in the drop down
menu (10X or 40X).
c. Draw a line by holding down the left click button and dragging the line the length
of the organism. When you let go, it should give the length in um. Mark this
number down on your chart. After getting this number, you may click on the X to
close this window out.
8. Use your dichotomous key to identify the organism that is on your slide.
Repeat steps 1-5 to identify as many different protists as you can find on your prepared slide.
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Name ____________________________
Conclusion/Analysis:
1. Would you expect all students to observe exactly the same shape when observing a live
amoeba under the microscope? Explain.
2. What is a pseudopod?
3. What two functions do the cilia provide for the paramecium?
a.
b.
4. Unlike the higher plants, plantlike protists do not have roots, stems, or leaves. Explain
why they do not require these structures.
5. Why do protists live in aqueous environments?
6. What three groups make up the kingdom Protista?
7. What characteristics distinguish plant-like protists from animal-like protists?
Information cited from the following websites:
http://www.microbe.org/microbes/protists1.asp
http://www.nmnh.si.edu/botany/projects/algae/AlgIntro.htm
http://www.usoe.k12.ut.us/curr/science/core/6th/sciber6/MICRO/PROTISTS/protists.htm
http://www.microbeworld.org/htm/aboutmicro/microbes/types/protista.htm
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Dichomotous Key Chart
Length of Protist
Drawing of Protist
Name of Protist
Color:
Color:
Color:
Color:
Color:
Color:
Color:
Color:
Color:
Color:
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Teacher notes:
1. Amoeba have no cell wall and form pseudopodia to move and feed. So as a pseudopodia
forms, the shape of the cell changes and the amoeba moves. Therefore, no two amoebas
will have exactly the same shape.
2. Cytoplasm-containing extensions of the protists plasma membranes.
3. a. It can move by beating its cilia
b. Digestion
4. The protists are mobile and therefore do not have roots and do not have cell wall made up
of cellulose so they do not have leaves or stems. They contain chloroplasts to produce
their chlorophyll.
5. Movement/mobility.
6. a. algae
b. protozoa
c. slime molds
7. Plant-like protists contain chlorophyll and are able to produce their own food (autotroph)
whereas the animal-like protists must rely on hunting and gathering to obtain food
(heterotroph).
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