BIO170 General Biology Freeman/Mac Leod FMCC
PROTISTS
Objective: After completing this exercise, you should be able to do the following:
 Describe the diversity of protists.
 Describe the key characteristics of 4 of the major eukaryotic lineages (Amoebozoa,
Excavata, Alveolata and Stramenopila).
 Identify representative organisms in those 4 major eukaryotic lineages.
 Identify prominent morphological structures of each organism observed.
Introduction:
Unicellular eukaryotic organisms originated over 2 billion years ago, and today they are found in
every habitable region of Earth. The enormous diversity of organisms, their numerous
adaptations, and their cellular complexity reflect the long evolutionary history of eukaryotes.
The protists have been called a “catch-all group” in the domain Eukarya. They included not
only the unicellular eukaryotes but also their multicellular relatives, like the giant kelps and
seaweeds.
Figure 1: 3-Domain Tree of Life System
The most familiar groups of protists, commonly called algae and protozoans, have been well
studied since the earliest development of the microscope. Therefore, one might assume that the
taxonomic relationships among these groups are well understood. However, their phylogeny
(evolutionary history) has been difficult to determine from comparisons of cell structure and
function, nutrition and reproduction. Recent molecular and biochemical research, particularly the
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ability to sequence ribosomal and transfer RNA genes, has provided strong new evidence for
reconstructing the evolutionary relationships among the protists.
The three-domain system is a biological classification introduced by Carl Woese in 1977 that
divides cellular life forms into Archaea, Bacteria, and Eukarya domains. Domains are further
divided into major lineages separated by morphology. In this lab, you will become familiar
with 4 of these lineages: Amoebozoa, Excavata, Alveolata, and Stramenopila.
The protists range in size from microscopic to macroscopic. Some of the large brown algae can
be 60 m long. Many protists have a characteristic overall form, organelles with distinctive
features, or both. All eukaryotes alive today, including all living protists, have a nucleus and
endomembrane system, mitochondria or genes that are normally found in mitochondria, and a
cytoskeleton.
As you examine the diverse samples notice how this taxon ranges from heterotroph to
autotroph, and from structurally simple (unicellular) to complex (multicellular). Autotrophic
organisms are able to convert the sun’s energy to organic compounds. Heterotrophic organisms
must ingest organic compounds via ingestion (uptake of large particles or whole organisms by
pinching inward of the plasma membrane). Traditionally, autotrophic protists are called algae
and heterotrophic protists are called protozoa. Some protozoa, euglenoids for example, are
mixotrophic, capable of photosynthesis and ingestion.
As you work through this lab, look for characteristics of each protist that are shared with
animals, plants and/or fungi. Most evolutionary biologists believe the remaining multicellular
kingdoms arose from protist ancestors. Determine the nutritive mode of each organism. Note
morphological characteristics of each example studied. Determine which characteristics are
found in the same clade and which are shared with other clades. What means of locomotion does
each organism possess? What role does it play in the ecosystem? Where does it live? What
taxon does each organism belong to and why?
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BIO170 General Biology Freeman/Mac Leod FMCC
Figure 2: Phylogenetic Tree of Eukarya
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BIO170 General Biology Freeman/Mac Leod FMCC
In this lab you will study the examples of groups of protists shown in Table 1.
Table 1: Groups of protists investigated in this lab exercise
Major Lineage
Major subgroup
Procedure
Excavata
Euglenida
A
Example
Genus
Euglena
Alveolata
Ciliata
B
Paramecium
Dinoflagellata
C
Peridinium
Diatoms
D
Thalassiosira
Diatoms
D
Mixed diatoms
Lobose amoeba
E
Amoeba
Stramenopila
Amoebozoa
THE EXCAVATA
Key features of the lineage Excavata are
1) A feeding groove on one side of the cell (the “excavation”).
2) Lack of mitochondria (evolutionarily, mitochondria were lost).
SUBGROUP EUGLENIDA
One sub group of this lineage is the Euglenida. These are aquatic organisms (both freshwater
and marine) that lack a cell wall. The cell membrane is supported by a unique set of proteins that
form a pellicle. Some are autotrophic (via photosynthesis) but most ingest their food. They
reproduce asexually.
The organism you will observe belongs to the genus Euglena. These organisms move by use of a
long flagellum (also possess a second flagellum), are unicellular, are mixotrophic and can be
found in fresh and salt waters.
Procedure:
1. Refer to Photo atlas p.18 as you do this exercise.
2. Obtain a prepared slide of Euglena and observe it using scanning, low and high powers of
the compound microscope.
3. Draw your specimen (indicate magnification) in your notebook and label clearly using
Fig 3 as a guide only (do not just copy):
 flagellum, chloroplasts, nucleus, eyespot, pellicle (thin layer supporting the
plasma membrane).
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BIO170 General Biology Freeman/Mac Leod FMCC
Fig. 3: Diagram of Euglena sp.
B. THE ALVEOLATA
Key features of the lineage Alveolata are
1) The presence of alveoli (small sacs located under the plasma membrane).
You will study 2 sub-groups of this lineage: the Ciliata and the Dinoflagellata
SUBGROUP CILIATA:
The Ciliata have cilia that cover their body. They require water to survive and so are found in
aquatic and wet terrestrial habitats (like wet soil). They have two nuclei: a large macronucleus
and a small micronucleus. Ciliates obtain food by ingestion. They reproduce asexually though
they also can exchange genetic material during the process of conjugation.
The organism you will observe belongs to the genus Paramecium.
Procedure:
1. Refer to Photo Atlas page 22.
2. Using the compound microscope, examine a living Paramecium. Place a drop of water
from the bottom of the culture on a clean slide. Add small drop of Protosol and then the
coverslip.
3. Observe your specimen using scanning, low and high powers
4. Describe the movement of your specimen. Is it directional or random?
5. Draw your specimen in your notebook (indicate magnification) and label clearly using
Fig 4 as a guide only (do not just copy):
 Oral groove, food vacuole, macronucleus, cilia
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6. Observe your specimen feeding by adding a drop of yeast stained with Congo red to the
edge of the coverslip (it will diffuse around the paramecia). Watch as the yeast moves
into the oral groove, gullet and food vacuole
Fig 4: Diagram of Paramecium caudatum
SUBGROUP DINOFLAGELLATA
Swirl your hand through tropical ocean waters at night and you may notice a burst of tiny lights
(bioluminescence). Visit a warm, stagnant inlet and you might notice that the water appears
reddish and dead fish are floating on the surface. Both of these phenomena may be due to
activities of dinoflagellates.
The subgroup Dinoflagellata is characterized by cellulose plates that contribute to their
characteristic shape. They have two flagella. One extends from the organism and the other is
found in a groove around the body of the organisms. The two perpendicular flagella help the
organism move through their environment.
Procedure:
1. Refer to Photo atlas p.21.
2. Obtain a prepared slide and prepare a wet mount of Peridinium.
3. Focus the slide using scanning power. You may have to switch to a higher power
objective to see them clearly
4. Detect locomotion in your living specimen
5. Observe the intricate geometric patterns using the prepared slide
6. Draw your specimen in your notebook (indicate magnification) and label clearly using
Fig 5 as a guide only (do not just copy).
 Flagella, nucleus, sulcus
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Fig 5: basic structure of Peridinium
C. THE STRAMENOPILA
Key features of the lineage Stramenopila are
1) The presence of hairs that cover the flagellum. This is present in at least one stage of
their life cycle.
SUBGROUP DIATOMS
One subgroup of the Stramenopila is the Diatoms. These organisms have silica rich “glassy”
cell walls that can be very ornate. They gain energy through photosynthesis and are the most
important photosynthesizers in cold marine waters. Their cell wall deposits are mined as
diatomaceous earth and have numerous economic uses (swimming pool filters, abrasive in
toothpastes and silver polish). Diatoms reproduce both asexually and sexually.
Diatom cells are either elongated, boat-shaped, bilaterally symmetrical pennate forms or radially
symmetrical centric forms. The cell wall consists of two valves, one fitting inside the other, in
the manner of the lid and bottom of a petri dish.
You will observe organisms from the genus Thalassiosira as well as “mixed” species of diatoms.
Procedure:
1. Refer to Photo atlas p.20
2. Prepare a wet mount of Thalassiosira and observe it using the compound microscope.
 Are you able to detect locomotion?
 Can you see chloroplasts?
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BIO170 General Biology Freeman/Mac Leod FMCC
3. Draw your specimen in your notebook (indicate magnification) and label clearly your
photo atlas as a guide only (do not just copy) and indicate its shape.
a. Cell wall, chloroplast
4. Obtain a prepared slide of diatoms and observe it using the compound microscope.
5. Observe the intricate geometric form using the prepared slide
 Are they centric, pennate or both?
6. Draw your specimen in your notebook (indicate magnification) and label clearly using
your photo atlas as a guide only (do not just copy) and indicate its shape.
a. Cell wall, chloroplast
D. THE AMOEBAZOA
Key features of the lineage Amoebozoa are
1) The lack of a cell wall.
2) The presence of pseudopodia (used for ingestion and movement).
SUBGROUP LOBOSE AMOEBA
Most Amoebozoa are unicellular and are common in soils and aquatic habitats.
One subgroup of the Amoebozoa is the Lobose amoeba. These organisms produce lobose
pseudopods; blunt extensions of the organism that are characterized by a clear ectoplasm and
granular endoplasm.
The species Amoeba proteus will be observed in this lab exercise. Amoeba proteus occupies
freshwater environments and feeds on algae, rotifers, and even smaller amoebae. Due to the
presence of phytochrome (pigment) A. proteus may appear in a variety of colors under the
microscope.
Procedure:
1. Refer to Photo atlas p.22
2. Obtain a prepared slide of Amoeba proteus and observe it using the compound
microscope.
7. Draw your specimen in your notebook (indicate magnification) and label clearly using
Fig 6 as a guide only (do not just copy).
a. cytoplasm, ectoplasm, endoplasm, pseudopodium, nucleus, food vacuole,
plasma membrane
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Fig. 6 Anatomy of an amoeba courtesy of Wikipedia
Synthesis
1. Complete the following Table (on the next page). Cut it out. Tape or paste it into your
notebook.
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BIO170 General Biology Freeman/Mac Leod FMCC
Comparison Table of Protists:
Major Lineage
Major Subgroup
Defining
characteristics
Examples from lab
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BIO170 General Biology Freeman/Mac Leod FMCC
Major Lineage
Major Subgroup
Defining
characteristics
Examples from lab
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