Name: ____________________
Chapter 11: Protists
Revised: Spring 2007
Learning Objectives:

Gain an appreciation of the diversity of organisms considered to be “protists.”

Describe differences between the major kingdoms of protists.

Understand some of the different methods used by protists for obtaining nutrients and for moving
about in the world.

Explain the key role that protists play in supporting life in aquatic communities, as well as sustaining
human life on the planet.

Understand what information is important for classifying
organisms.
Contents:
Introduction ............................................................................................................... 146
Ecological Importance of Protists ............................................................................. 147
Exercise 1: Protozoa ................................................................................................. 148
Ciliated Protozoa ........................................................................................... 148
Paramecium ....................................................................................... 148
Stentor................................................................................................ 150
Amoeboid Protozoa ....................................................................................... 151
Exercise 2: Algae ...................................................................................................... 152
Green Algae ................................................................................................... 153
Chlamydomonas ................................................................................ 153
Volvox ................................................................................................ 154
Spirogyra ........................................................................................... 154
Ulva ................................................................................................... 155
Diatoms.......................................................................................................... 155
Dinoflagellates ............................................................................................... 156
Brown Algae .................................................................................................. 157
Red Algae ...................................................................................................... 157
Euglenoid Algae ............................................................................................ 158
Exercise 3: End of Lab Questions ............................................................................ 159
Exercise 4: Protist Review Worksheet ..................................................................... 160
protists:
145
INTRODUCTION
Protists are eukaryotes, but beyond that, they are difficult to classify. The group of organisms that fit
into the “protist” category has more than 7 kingdoms and 10,000 species. About the only thing they all have
truly in common is that they are all eukaryotes. They also are all similar in having a less complex
organismal organization than the fungus, plants, or animals. To make more sense of this catch-all group, it is
divided into three major groups. These groups are:
1. The protozoa - single celled animal-like protists.
2. The algae - plant-like protists.
3. Slime molds - fungus-like protists.
Note that these are also informal group names, like “protist,” and not official classification taxa. You
already studied protists a bit during the Diversity Lab at the start of this semester. You will continue to study
protists here and learn about some of the formal Kingdom and Phylum names that may (or may not) remain
in place. However, in this lab, we will restrict our further study to the protozoa and algae, and we will not be
viewing examples of slime molds.
Why is it that we have so much trouble classifying these organisms? You tried to classify many of
them during the Diversity Lab, but may remember that it wasn’t easy. The quick answer as to why it is so
difficult is because we have only recently developed the appropriate methods to classify them properly! You
see, years ago, people came up with a classification scheme based on readily observable organizational
features. Before the 1900s, we classified all living things as either plant or animal. Then we observed
fungus more closely and realized that they were too different from plants to be grouped with them. As our
microscopes improved, we learned about microscopically-small organisms, and tackled grouping them as
well; this was when the name “protists” arose. By the mid-1900s, we had learned that there were different
types of cells, and by the later 1900s we determined that there were different kinds of prokaryotic organisms
(thus, Domain Archaea and Domain Bacteria were named). However, observable organismal characteristics
are not the only ones we can now use. We can now directly compare the DNA from different organisms to
decipher their relatedness. The more similar the genetic code between two species, the more closely related
they are.
It turns out that not all organisms that look similar are closely related! You can probably relate to this
notion if you think about the fact that while some human siblings look similar, others don’t look at all
alike—and yet they are still siblings and very closely related. It is the genetic code of the organisms that
provides the key to understanding how related different organisms truly are. We have only learned how to
obtain the genetic code of organisms quickly and easily in the last 15 years with the international effort made
on the Human Genome Project. Therefore, now we have a lot of new data to look at and re-evaluate
organismal relatedness. This new information is going to help us shape our taxonomic classification, and
make it more accurate. Until that time when we know exactly how many kingdoms lie within the informal
grouping called the protists, we will have to just do our best to try to understand these organisms.
protists:
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Ecological Importance of Protists
While responsible for causing many dreaded human diseases (malaria, sleeping sickness, and giardiasis to
list a few), protozoa also benefit humans tremendously. Protozoa are important nutrient recyclers in natural
ecosystems. Without organisms like bacteria, fungi and protozoa, soils would quickly become depleted of
nutrients making plant growth impossible. All organisms on earth depend on healthy plant populations for
survival. Protozoa also play a key role in wastewater treatment plants by consuming enormous quantities of
bacteria, and are important components of food chains.
Algae is much more than simply "seaweed" or "pond scum"--it is a vital component of our biosphere, and the
survival of humans would be jeopardized without it. We often hear of the rain forests as being important in
making oxygen, and they are important in many ways, but most of the oxygen we actually breathe is made
by algae in the ocean. Indeed, algae produced more than 50% of the oxygen molecules that your cells
consumed during this laboratory! Algae also form the base of aquatic food chains. This algae is primarily
microscopic, and is called phytoplankton. Without algae in lakes, rivers, and oceans, there could be no life
in these environments since all aquatic life either directly feeds on algae, or feeds on organisms that feed on
algae. Humans usually eat from the top of the food pyramid. Without phytoplankton in the oceans, salmon,
tuna, cod, shrimp, lobsters and a myriad of other seafood products would not be available to us.
An Aquatic Food Chain
1000 pounds of algae
(phytoplankton).
100 pounds of
zooplankton.
protists:
10 pounds of small fish.
147
1 pound of large
fish for dinner.
Exercise 1: The Protozoa
Protozoa are single-celled, heterotrophic organisms. Although most are single celled, that one cell
is still able to carry out all the functions necessary for life: ingesting and digesting food, expelling waste, and
obtaining oxygen.
Protozoa live just about anywhere that is moist, on both land and sea, but in this lab we will primarily
be looking at protozoa that live in fresh water environments.
Protozoa that live in fresh water face a problem;
compared to the surrounding water the high
concentration of solute in their cells creates an osmotic
gradient. Which way do you think the water moves in
this gradient? Protozoa respond to this problem with a
contractile vacuole. The contractile vacuole is a cellular
structure that constantly pumps water out of the cell.
There are so many different protozoa, it’s not easy to
divide them up into species. The current approach is for
taxonomists to classify protozoa according to their
method of movement, and it is the mode of locomotion
on which we will base our study of the protists today.
Contractile vacuole in a
paramecium. Note the array
of channels that carry water
to the central vacuole.
Ciliated Protozoa
Ciliates are protozoa that move and obtain food by means of short, hair-like structures called cilia. It
is thought that they fit into Kingdom Alveolata. A cilium (singular) extends from the cell membrane and is
composed of bundles of microtubules. In most ciliates, cilia cover the entire cell surface. Protozoa use their
cilia for two purposes:
1. Locomotion
2. Feeding. The cilia sweep smaller protists, bacteria, and non-living organic matter into an oral
groove on the cell surface. At the far
end of the oral groove, a food vacuole
forms. Ciliates occupy a variety of
habitats including freshwater, soil and as
symbiotes in the guts of invertebrates.
 Study of Paramecium - Prepare a wet mount
of living Paramecium. Add methyl cellulose
to your wet mount to slow the Paramecium
down. View using 10x magnification.
Paramecium will be gray or tan and will move
quickly in a spiraling manner.
Find a
Paramecium that cannot move and observe this
individual under 40x magnification.
protists:
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 Questions about Paramecium.
 Do the cilia beat in a synchronized pattern, or does each just beat on its own? ________________
 Explain why Paramecium’s body spirals as it moves through the water?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
 Look for contractile vacuoles within each cell. What collects within the contractile vacuoles of the cell?
__________________________________________
 Why are contractile vacuoles are needed by these organisms (hint: think in terms of osmotic gradients)?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
 Please explain what might happen to Paramecium if the contractile vacuoles stopped functioning?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
 The following two graphs show how many times Paramecium’s vacuole might contract in pond waters of
varying saltiness. One graph is correct and the other is not. Circle the correct graph. Explain your
choice on the next page.
Circle the correct graph.
6
6
5
5
Graph A
Contractions 4
per minute.
Graph B
Contractions 4
per minute.
3
3
2
2
1
1
0
1
2
3
0
4
1
Less salty
More salty
Saltiness of pond water.
protists:
2
3
4
Less salty
More salty
Saltiness of pond water.
149
 Did you circle Graph A or Graph B on the previous page? ______________________________
 Please explain your choice. _____________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
 Sketch a Paramecium in the space below the way it looks to you. Label your sketch.
 Study of Stentor: Prepare a wet mount of living
Stentor. Add methyl cellulose to your wet mount to
slow the movements of these very large organisms. You
will be able to see these using only your scanning power
objective. Once you find one, increase your
magnification to answer the questions below. Food
vacuoles should be apparent in these organisms.
Stentor
 Are the cilia the same all over the cell, or are they more
dense in some areas. Explain. ________________________________________________________
_________________________________________________________________________________
 Sketch a Stentor in the space below the way it looks to you. Label your sketch.
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Amoeboid Protozoa
Amoeboid protozoa are a large group that includes the amoebas. Amoebas move using pseudopodia.
Pseudopodia are protoplasmic extensions that pull the organism in a particular direction. Amoebas also use
these "false feet" to capture food through a type of endocytosis known as phagocytosis. Most freshwater
environments include harmless species of amoeba, and it is one of these we will be observing today. In
addition to slow moving streams and ponds, Amoeba species also inhabit soil and saltwater and a few even
live as parasites in the digestive systems of humans and other animals.
 Study of Amoeba - Make a wet mount of Amoeba. Using your scanning objective, scan your slide for
a grayish, irregular-shaped object. Reducing your light intensity may help you find this organism.
Don’t be fooled by dead vegetation, which is yellowish brown, the amoebas you are looking for are more
grayish black. If after a few minutes you have still not located an amoeba, rinse your slide and try
another drop. Persistence is the key to finding these organisms!
 Note the irregular shape, the slow movement (streaming) of the protoplasm, and the formation of
pseudopodia.
 List 2 functions of pseudopodia __________________________________________________________
____________________________________________________________________________________
 Do you see any food vacuoles? If so, describe their appearance. ______________________
___________________________________________________________________________
 Do you think it is likely that amoeba require contractile vacuoles? Please explain your answer.
___________________________________________________________________
__________________________________________________________________________
__________________________________________________________________________
 Sketch an Amoeba in the space below the way it looks to you. Label your sketch.
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Exercise 2: The Algae
Algae are autotrophic (photosynthetic) organisms. Like the
protozoa, some algae are single-celled. Unlike the protozoa
however, many algae are multicellular and may be quite large. Most
algae live in water, but they may also be found in any place that is moist at
least part of the time. Algae are around us all the time and can be found on
shady brick walls, the fur of some mammals, in swimming pools, birdbaths,
flowerpots, and gutters on the roof.
Over 30,000 species of algae have been described by Phycologists (Phycology is the study of algae). Like
the protozoa, taxonomists need a way to divide up all these species. The way they do it is by color and by
how complicated the algae is.
Divisions of algae by color.
Different species of algae use different types and mixes of chlorophyll and this leads to their being
different colors. Based on color, there are four main groups of algae. They are:
A. Green algae
B. Brown algae
C. Golden-brown algae
D. Red algae
Look at the seaweed the next time you’re at the beach. The four colors are usually pretty easy to find.
Divisions of algae by complexity.
In addition to being different colors, some algae are more complex than others. Algae can be divided
into the following four categories based on the complexity of the organism:
A. Unicellular algae Consist of only one cell living on its own.
B. Colonial algae
Consists of a colony or cluster of more or
less identical cells. Each cell could live on
its own, but they choose to live together.
C. Filamentous algae Consists of a long chain of more or less
identical cells. Again, each cell could live
on its own, but they choose to live
together.
D. Multicellular algae These are diverse, since they may be very
simple (where all the cells look similar) or
they may be more complex (and have
specialized cells). Large seaweed, for
example, has special cells that form rootlike holdfasts to hold on to rocks.
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152
Groupings of algae by genetic comparisons into Kingdoms
A. Kingdom Euglenozoa
These algae are motile (using flagella) and can either eat like a
protozoan or carry out photosynthesis.
B. Kingdom Stramenopila
This group contains the brown algae, the diatoms and other
groups.
C. Kingdom Rhodophyta
This group contains the red algae.
D. Kingdom Alveolata
Although we saw this kingdom back in the protozoa section as the
group that contains ciliates, it also contains the dinoflagellates.
E. No Green Algae!
The green algae have been temporarily re-assigned into the
Kingdom Plantae as Division Chlorophyta. These organisms may
stay in with the plants, or may return to the group of protists as
their own kingdom.
Question: Which of
these products
contains algae?
Answer:
They all do!
Green Algae
Chlamydomonas
Chlamydomonas is algae, but it has an eyespot to detect light and
flagella to swim toward the light. It’s a good example of how it is
hard to fit protists into categories. Each cell also has a granule of
stored starch and two flagella.
 Examine a living specimen or prepared slide of
Chlamydomonas beneath your microscope. Note their small
size. Identify flagella and the starch granule if possible.
 To which of the 4 color categories does Chlamydomonas
belong? __________________________
 To which of the 4 complexity categories does Chlamydomonas
belong? __________________________
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153
Volvox
Each of the cells in Volvox also has a flagella. Flagella are beat by
individual cells in synchrony with other cells. This allows the whole
Volvox to move through the water in an orderly manner.
 Prepare a wet mount of Volvox. If available, use a depression
slide for Volvox so it is not crushed by the coverslip. Note the
daughter (reproductive) colonies that may be seen inside some
Volvox.
Volvox
 To which of the 4 color categories does Volvox belong?
__________________________
 To which of the 4 complexity categories does Volvox belong? __________________________
 Sketch a Volvox in the space below the way it looks to you. Label your sketch.
Spirogyra
Spirogyra is what we may think of as "pond scum", since it forms thick
mats on the surface of ponds when conditions are right. Spirogyra takes the
form of thread-like strands called filaments. Each filament is composed of
many cells linked end to end. Spirogyra gets its name from the fact that the
chloroplasts inside the cells are arranged in distinctive spirals.
 Prepare a wet mount of Spirogyra and examine beneath the
microscope. Note the characteristic spiral-shaped chloroplasts. Look
for a nucleus within each cell of the filament. The nucleus is
suspended in strands of cytoplasm, much like a spider might be found
sitting in the center of a web.
Spirogyra
 Note the filamentous shape of the algae. Are the filaments branched? _________________
 Can you see cell walls separating the individual cells of the filament? _________________
 To which of the 4 color categories does Spirogyra belong? __________________________
 To which of the 4 complexity categories does Spirogyra belong? __________________________
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 Sketch Spirogyra below and label any visible features.
Ulva
An abundant marine species of algae is "sea lettuce" or Ulva. The body or thallus of Ulva includes a tiny
root-like holdfast that anchors the algae onto rocks or other substrate on which it is growing. The thallus of
Ulva is only several cell layers thick.
 Observe the living specimens of Ulva on display in the lab.
 To which of the 4 color categories does Ulva belong? __________________________
 To which of the 4 complexity categories does Ulva belong? __________________________
Diatoms
Diatoms usually have very small cells and are found in
abundance in both terrestrial, marine, and freshwater
environments. The defining characteristic of diatoms is the
presence of their glass-like cell walls or frustules composed of
silica. The walls are arranged in overlapping halves, much like
candy box or petri dish fits together.
Electron microscope picture of a diatom's
frustule. An incredibly complex shell for a
creature that is only one cell!
a
Once the organism dies, the cell inside decomposes but the glasslike frustule remains intact for hundreds or thousands of years.
Over thousands of years significant deposits of frustules may
accumulate on the ocean floor. These deposits may then be mined
to provide diatomaceous earth. Humans use this material in a wide
array of products, including paints, cement, fertilizers, toothpaste,
polishes, and cleaners. Diatomaceous earth also kills snails and
slugs. Examine the diatomaceous earth on display in lab.
 Examine prepared slides of diatoms or, if available, prepare a wet mount and examine sediments for
both living and dead diatoms.
 Note the many shapes. To which of the 4 complexity categories do Diatoms belong? ________________
protists:
155
 Sketch a few diatoms below, in the area between the photos of diatoms:
 To which of the 4 color categories do Diatoms belong?
________________
 To which of the 4 complexity categories do Diatoms belong? ________________
Dinoflagellates
Dinoflagellates are unicellular algae that move with two
flagella. Because of the positioning of their flagella, they tend to
whirl about in the water. The prefix “dino-” means whirling, so
they are named according to the way they move. Although
dinoflagellates move, they are also autotrophic. They are also
algae because they have very interesting cell walls made up of
many plates like armor. Their two flagella have to stick out
through grooves in their cell plates.
 Observe the living specimens of Peridinium available in the
lab.
 To which of the 4 complexity categories does Peridinium
belong? __________________________
protists:
156
Brown Algae
Laminaria and Fucus are types of kelp. Kelps are typically dark brown in
color and are only found in marine environments. They generally prefer
cooler oceans over warm. Each individual kelp is composed of a basal
holdfast, which anchors the organism, blades which look and act like leaves,
and a stalk-like stipe. Keep in mind though, that kelp are not plants because
they lack true stems, leaves and roots. Distributed along the blade may be
several or many air bladders that help to keep the blade buoyant.
A thick growth of kelp can create an underwater forest along many temperate
shores. Kelp forest are extremely important ecologically because they create
an environment where marine mammals, fish, and invertebrates can hide, raise
their young, and seek protection from storms.
 Observe living specimens of kelp on display. Make a sketch in the space
below. Include and label on your sketch: Holdfast, blade, and stipe. If
time allows, make a wet mount of a small section of the blade, and draw
the cells you see below as well.
 To which of the 4 color categories does kelp belong? __________________________
 To which of the 4 complexity categories does kelp belong? __________________________
Red Algae
Callithamnion is a filamentous algae of the type that can often be found floating in the surf along New
England shores. A commercially important species related to Callithamnion is Irish Moss, which is a source
of the carageenan used as a thickener in many food products. You may also have the opportunity to see
Chondrus crispus, which is a larger multicellular organism.
 Observe the living specimens of Callithamnion on display in the lab.
 Note the filamentous shape of the algae. Are the filaments branched? _________________
 Can you see cell walls separating the individual cells of the filament? _________________
 To which of the 4 color categories does Callithamnion belong? __________________________
protists:
157
 To which of the 4 complexity categories does Callithamnion belong? __________________________
 Sketch Callithamnion in the space below the way it looks to you. Label your sketch.
Euglenoid Algae
Study of Euglena - Euglena are freshwater protists that exhibit characteristics of both
protozoa and algae. Algal characteristics include the ability to photosynthesize and store
starch. Protozoan characteristics include the lack of a cell wall, and the ability to ingest food.
Some species of Euglena are very tolerant of polluted waters, and act as water quality
indicators for humans when expensive pollution monitoring equipment is not available.
 Prepare a wet mount of Euglena. Methyl cellulose will help slow these fast-moving organisms.
Reduce the light with the iris diaphragm and work up to your 40x objective. Find an individual that
cannot move and note the movement of the flagellum. Look for the red stigma or “eyespot” near the
flagellum. This structure allows the organism to sense different light intensities. Note the very flexible
external membrane or pellicle, as well as green coloration of the organism that indicates the presence of
chloroplasts.
 Why is a structure such as the stigma important for photosynthetic organisms like the Euglena?
____________________________________________________________________________________
 Do you think Euglena require contractile vacuoles?
Explain.
_______________________
____________________________________________________________________________________
 Chlamydomonas is a lot like Euglena in many ways. There is another organism we have seen today that
also shares some similarity to Euglena. What other organism has traits in common with Euglena and
what are the traits?
___________________________________________________________________________________
___________________________________________________________________________________
___________________________________________________________________________________
 To which of the 4 complexity categories does Euglena belong? __________________________
 Note that you were not asked to put Euglena into a color category… that is because this organism is NOT
a green algae, but is in a different phylum, the Euglenoids.
 Sketch a Euglena in the space below the way it looks to you. Label your sketch.
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Exercise 3: End of Lab Questions
You may have to consult other sources of information to correctly answer some questions.
1.
Approximately 100,000 species of protists have been identified and classified. Most taxonomists,
however, believe that this number is low and that many thousands more await discovery by humans.
Explain why you think it is so hard to find new species of protists.
2.
List functions of the following: Pseudopodia, flagella, chloroplast, stigma, holdfast, cilia, food vacuole,
contractile vacuole.
3.
Suppose that as the result of extensive pollution to the ocean, kelp forests are killed. Explain how this
would affect not only kelp populations, but also many other forms of marine life.
4.
Why are protozoa not classified into the animal kingdom? List 2 reasons.
5.
Why are algae not classified into the plant kingdom? List 2 reasons.
6.
What is agar? Carrageenan? Algin?
7.
List 3 ways an amoeba is similar to a human.
8.
List 3 ways humans and Paramecium differ.
9.
Protozoa are: Heterotrophic or Autotrophic? Define your answer.
10. On your first day on the job as Naturalist at Cape Cod National Seashore, an angry visitor approaches
you complaining about all the "good fer nuthin seaweed" littering the beach. In a paragraph, explain to
the visitor 5 ways humans benefit from algae.
11. If both protozoa and most bacteria are single-celled and heterotrophic, why are they classified into
separate kingdoms? Explain.
12. Paramecium possesses unique organelles called trichocysts. See if you can find out what these are and
their function.
13. Suppose that as a result of a genetic mutation a particular freshwater protozoan loses the use of its
contractile vacuole. Is this organism likely to survive, reproduce, and pass this characteristic on to its
offspring? Explain.
protists:
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Exercise 4: Protist Review Worksheet
protists
Protozoa
Brown Algae
Dinoflagellate
Multicellular
Euglenoids
UniColonial
FilaMulticellular
mentous cellular
Diatoms
UniUniUnicellular cellular cellular
Red Algae
Green Algae
Flagellates
Ciliates
O
r
g
a
n
i
s
m
Amoebas
G
r
o
u
p
i
n
g
Algae
MultiUniUniUniMulticellular cellular cellular cellular cellular
no
example
given
Organisms you may have seen today:





protists:
Spirogyra
Chlamydomonas
Euglena
Stentor
Chondus Crispus
160





Amoeba
Fucus or Laminaria
Paramecium
Callithamnion
Volvox



Ulva
Diatoms
Peridinium
Put each organism you saw into an
organism box above to organize all that
you viewed!
protists:
161