Name: ____________________________________________
Period: _______________
Biology LAB: Microscopic Investigation of Protists
Wherever you find water, you will likely find one-celled organisms of the Kingdom Protista. Although these protists
are unicellular, they each perform the same life functions as most multicellular plants and animals that you may be
more familiar with. Protists produce energy from food, exchange gases, get rid of wastes, respond to their
environment and reproduce. Many protists are motile. In this investigation, you will compare the structure, behavior
and methods of movements of three motile (in some cases very motile!) representatives of the Kingdom Protista.
Pre-lab
1. Read through the instructions for the investigations and answer the Pre-lab questions.
2. Label the structures of Euglena, Amoeba and Paramecium. Your textbook will be helpful for this.
Investigation Procedure
PART A: Euglena
1. Form a small (a bit smaller than a dime) circle of Proto-Slo on the center of a clean slide. Using ONLY the
dropper labeled “E” for euglena, obtain a drop from the euglena culture and place it within the ring of ProtoSlo. Cover carefully with a coverslip, minimizing air bubbles (a few air bubbles are okay because they
provide a focus guide).
2. Place the slide under a microscope and observe under LOW power to locate some euglenas. At this
magnification, euglenas appear as tiny slivers of green. If they are not trapped in the Proto-Slo, they will be
swimming in lazy circles and spirals. Move the slide so that a euglena that is not moving or moving only
slowly is centered on the slide. Switch to medium power, refocus and re-center the specimen, then switch to
high power for your detailed observation.
3. Observe your euglena for several minutes, following its movement by adjusting the fine-focus up and down
and moving the slide slightly if needed to maintain the euglena in view. Make note of how the euglena moves.
Study its structure, color and shape. Answer the questions in Part A of the lab report.
4. In the space provided, draw the euglena under high power including as much detail as possible. Label the end
of the euglena that moves first as front.
5. Carefully clean the slide and coverslip and reuse for Part B and C of the investigation.
PART B: Amoeba
1. Using ONLY the dropper labeled “A”, carefully take a small drop from the bottom edge of the culture jar. Be
careful not to stir the culture. Place the sample on a slide and cover with a coverslip. Proto-Slo is not needed
for amoebas. Observe under low power to locate an amoeba. Unlike euglena, amoebas are relatively large (at
least in the unicellular world) and are easy to find under low power, if they are present. Unfortunately, while
amoebas are sizeable enough to easily be seen, most cultures do not have a large number of them in it so it
may take several slides before you find one.
2. Center the amoeba and switch to high power to observe the amoeba’s structures and method of movement.
Answer the first 5 questions in Part B of the lab report.
3. Return the slide to low power and re-center the amoeba. Allow the slide to sit for five minutes without being
disturbed, then observe the amoeba again. Answer questions 6 and 7 from part B.
4. If you have found a good amoeba, ask other students if they wish to use your slide when you have finished. If
no one needs your specimen, carefully clean the slide and coverslip.
PART C: Paramecium
1. Apply Proto-Slo to the slide as described in part A. Using ONLY the dropper labeled “P”, take a sample from
the jar of paramecium. If there is food or debris in the culture jar, put the dropper tip near that debris when
collecting the sample and you are far more likely to get paramecia to observe.
2. Scan your slide on low power to find a paramecium. Those in the middle of the slide will be swimming
rapidly; hopefully some nearer the edge will be bogged down by the Proto-Slo. Observe a free-swimming
paramecium under low power and answer questions 1-2 in part C.
3. Find a trapped paramecium and observe it under high power (moving the magnification in steps as described
in Part A). In the space provided, draw a paramecium under high power with as much detail as possible.
Label the end of the paramecium that moves first (most of the time) as front.
4. If time permits, ask your teacher for a red-stained sample of yeast. Add some red yeast to a paramecium
sample and observe under low power (do NOT add Proto-Slo). You should be able to observe paramecia
feeding and be able to answer question 4 of Part C.
CLEAN-UP
1. Clean your slide and throw away the coverslip in the glass disposal box in the room. Return the clean slide
neatly to the box. Wipe any spills in your area, pack up the microscope following correct storage procedures
and return it to the cart.
2. Complete the protist comparison chart and answer the concluding questions.
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Pre-Lab Questions
1. What is a protist?
2. Define autotroph.
3. Define heterotroph.
4. Why is the low-power objective lens used to scan a slide rather than the high-power lens?
5. Proto-Slo is a viscous (thick) liquid. What is its purpose in this lab? Why is it not needed with the amoeba?
6. Label the parts of the three protists.
A. euglena
B. amoeba
C. paramecium
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INVESTIGATION
Observations and Data
PART A: Euglena
1. Describe the general shape of the euglena. Other than moving, does the shape ever change? Explain.
2. Describe the color of the euglena. Explain why it has this color.
3. How does the euglena obtain its food?
4. In what way(s) is the euglena’s pellicle similar to the silica cell wall of a diatom and in what way(s) different?
5. The euglena can move by two methods. Describe each.
6. Draw a euglena under high power with as much detail as you can.
_________ X
PART B: Amoeba
1. Describe the amoeba’s shape and color.
2. Describe the process by which an amoeba takes in food.
3. How does an amoeba move?
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4. Based on your observations, describe how pseudopods are formed.
5. Could you label a particular side of the amoeba as “front”? Explain.
6. After five minutes, was the amoeba still in the field? Compare the shape of the amoeba before and after the
five minutes.
7. Why do you think the amoeba responded the way it did?
PART C: Paramecium
1. Describe the color and shape of the paramecium.
2. Describe the movement of a paramecium as it zips around your slide (use low or medium power for a bigger
field of view). Is it completely random? Can you determine if anything is “guiding” their movements?
3. Draw a paramecium under high power with as much detail as possible.
_________ X
4. Describe how the paramecium takes in food.
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SUMMARY
Common
Name
Phylum
Autotroph or
Heterotroph
Shape
Relative Size
Method of
Movement
Method of
food-getting
Euglena
Amoeba
Paramecium
ANALYSIS AND CONCLUSION
1. Where does each of the three organisms studied in this lab “fit” into the environment? What is their niche?
2. Of the three protists, the only one with a sensory organ is the euglena. What is this structure and why is it so
important to the euglena?
3. All of the protists in this lab have contractile vacuoles. What is the function of contractile vacuoles and why
do these protists need them?
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